I'm puzzled by Espressif's naming here. We had the ESP32-S3, so "S31" sounds like "S3, variant 1," but this part doesn't really look like a simple S3 variant. And then there's an ESP32-E22, but no E21 or even a plain E2 anywhere.
It was because IA-64 was a completely different unrelated architecture that until AMD succeeded with K8 was "the plan" for both 64bit intel roadmap and the roadmap to kill off compatible vendors (AMD, VIA)
They claim that the chip has an "MMU". But unfortunately this doesn't seem to be a true RISC-V MMU (according to the Sv32 specification) integrated into the CPU core itself, but just a peripheral designed for memory mapped SPI flash and PSRAM. So as far as I understand there is no true process isolation with page faults and dynamic paging.
Maybe Espressif will notice that there are no RV32 chips with MMU so far (at least to my knowledge); we only have 32 bit MCUs or then only 64 bits for the CPUs. Something like Cortex-A7 is missing.
Baochip looks very interesting, and I highly respect bunnie's work, but I can't realistically say Baochip is a viable option for me, an unprofessional tinkerer.
I'm not sure why you are not sure - S3 was using Cadence's Xtensa 32-bit LX7 dual-core microprocessor, but the article on S31 only mentions "dual core" without too much detail.
That's the SoC. The CPU is a small part of it. For example they could be using an open source design like the CVA6, or a commercial design from someone like Andes.
Nah, ESP32's have had ethernet capability for a while and ESP-IDF supports it well. I've been using one I built for 5+ years now. Unfortunately RMII (ethernet phy) interface takes up a lot of the GPIO pins. This part looks like it'll remedy that issue.
There's two ESP32 boards that have been around for a while with PoE:
> I'm more hopeful for single-pair ethernet to gain momentum though!
I keep looking for a reasonably priced 10baseT to 10Base-T1L bridge... everything commercial seems too expensive (for me) and the two hobby designs [1] [2] I've seen are not orderable :(
But I'm seeing more commercial options lately, so that's hopeful.
Multidrop SPE isn't going to outperform newer CAN versions though. Somewhere in the sub-100Mb/s (e.g. 10-20Mb/s range) is the practical maximum speed of a multidrop bus at useful lengths, and that essentially applies equally to CAN or SPE. The only way to really get faster in a "multidrop-like" sense is with logically loop-like systems like ethercat and Fibre Channel where each network segment is point-to-point and the nodes are responsible for the routing.
On that note, why does the PoE capability often add such a big proportion of the price of various items? Is the technology really costly for some reason, or is it just more there's fairly low demand and people are still willing to pay?
PoE is not obvious to implement (take it from someone who has done it with a fair share of mistakes), uses more expensive components that normal ethernet, takes up more space on the board, makes passing emissions certification more complex, and is more prone to mistakes that ruin boards in the future, causing support/warranty issues. In other words, a bag of worms: not impossible to handle, but something you would rather avoid if possible.
I wouldn't call it "better", but the least-effort path among hobbyists and low end gear is often 12v or 24v sent over a pair with Gnd and a forgiving voltage regulator on the other end.
A full-module add-on in this power class is about $7 at 1,000 unit scale [0]. It would be around $3 with your own custom PCB design in terms of BoM addon at scale. That’s power only. Add another dollar or two for 10/100 PHY.
The trick is as others have said in what adding it to your design does in terms of complicating compliance design.
PoE power supplies need to be isolated (except in rare exceptions) and handle much higher voltages than common USB-C or wall wart power supplies.
They have to use a transformer and a more complex control strategy, not a simple buck regulator with an inductor. PoE inputs need to tolerate voltages several times higher than the highest USB-C voltages, so more expensive parts are used everywhere.
Any Ethernet (well, any RJ45 you expect in a home/office) has to have at least 1500V isolation from the RJ45 wire to anything metal that can be touched or is a connector on the device.
A PoE-only device with no electrical connectors besides the RJ45 can just use a very cheap RJ45 port with integrated magnetics and PoE allowance (tiny bit bigger wires and a center pin exposed, less than 50ct more than the cheapest RJ45 with integrated magnetics) and a cheap buck from 40~80V to e.g. 5V.
Oh, and a cheap bridge rectifier and some signaling resistors to take care of input polarity and signal to the source that we in fact want the approximately 50V that could hurt a device not made for it.
That’s not a cheap buck lol. Order of magnitude more expensive then 12v not even mentioning capacitors that can withstand 80v is $$$ and your derating goes to shit
It sounds like the PoE spec was designed before the arrival of “IoT” type things like the esp32, raspberry pi’s, etc.
How much of the complexity is a “fundamental electrical engineering problem” and how much of it is just a spec written to solve a different set of problems?
Whenever you combine two things into one, the complexity and cost go up considerably. A regular coffee machine is pretty cheap. Add high pressure so it can make espresso and it gets considerably more expensive. Add milk so it can make cappuccino, again more complex and expensive. The same holds for electronics. Isolating power when it's alone is fairly straightforward. It gets considerably more tricky and hence more expensive the moment you want to place any kind of a meaningful data signal in its vicinity.
Can't you run a 5V supply from where your router is all the way to every god damn device in your house, and then pretend the wifi is also going through it? If you just want it to be inconvenient, there's no reason to let a lack of PoE stop you!
> You don't need long cables, just a local power source
Which means batteries that have to be replaced and maintained or cables... So ethernet with PoE or even better SPE (single pair Ethernet) with PoDL (power over data lines which is PoE for SPE) is the best from my point of view
I mean, if I just look at my house. There is just one ethernet outlet, but many power sockets. If I want to connect devices all over my house, the best way is to use wifi and usb power adapters. Not ethernet.
Both solutions require 1 cable per device, but the first solution would require only short and thin cables, and the second solution would require very long cables which I don't know even how to do properly without milling my walls.
Yep. Mains electricity is ubiquitous, highly interoperable, very reliable, very high power available per drop, can be outdoor capable, common standards, understandable by users, requiring no active components, with many on-call experts available who can come to fix problems or extend/alter connectivity. Mains power wall plates with inbuilt USB power outlets are even available at quite small cost if the look of the bigger plug and wiring is not appealing.
PoE is much fewer of those things. Difficult to recommend it these days with wifi being fast and reliable and so widely used. Certainly not for average residential user.
That's half the equation. The other half is the reliability and security of wifi, which is less than that of ethernet for people without physical access to my wall innards
Reliability of wifi is not as good I guess, although these days it is extremely good for decent devices. For poor quality devices, I have also heard of PoE routers blowing ports and devices that don't work properly.
Is security of wifi an actual practical concern? I've not heard of it since WPA2.
For average residential user, even most hobbyist / enthusiast, I doubt those things will matter. Almost everybody who wants extremely fast reliable wired connectivity will be much better off using fiber, and using wifi for cameras and automation and streaming and other such things. Getting power to where you need it is not the difficult part, especially if you're pulling wires anyway, which is why PoE has always been fairly niche.
Pretty niche requirement for personal user though. Protection against eavesdropping is the main thing required, and PoE is actually much worse for that than WiFi is you have any drops in less secured ares (e.g., outdoor cameras).
I can see that. I have security devices on my network (e.g. a camera), so I might come at this with a different perspective (since it's not uncommon for burglars to jam wifi).
On the other hand, _all_ the WiFi devices that I had at some point fell off the network, at least once. Including doorbells and cameras. While PoE devices just work.
Another point is that mains power in my area can go down periodically. My PoE switch is powered by a Li-Ion UPS and can provide power for about a day.
> On the other hand, _all_ the WiFi devices that I had at some point fell off the network, at least once. Including doorbells and cameras. While PoE devices just work.
I've not had that in a decade, and only for really shitty devices. I've also had crappy PoE devices stop working, ports blow. Too much effort to be worth the bother for me nowadays. If I had to bet my life sure I'd probably use wired ethernet. But if I had to bet my life I wouldn't be using PoE for power either.
UPS is entirely possible to do on residential mains circuits.
> I've not had that in a decade, and only for really shitty devices. I've also had crappy PoE devices stop working, ports blow.
Every ESP32-based WiFi device _will_ at some point get stuck in the disconnected state. It's almost an ironclad guarantee.
> UPS is entirely possible to do on residential mains circuits.
Sure, but then you're getting into the "whole house" backup with subpanel, transfer switches, etc. You can install backup for your router as a small UPS, but then I also have cameras, doorbells, sensors, etc.
If you already have a house without Ethernet wiring, then opening up the walls just to run PoE makes no sense. But if you're building a new house or if you have pre-existing wiring (and a lot of newish houses do), then PoE is a no-brainer.
> Every ESP32-based WiFi device _will_ at some point get stuck in the disconnected state. It's almost an ironclad guarantee.
See earlier note about crappy devices.
> Sure, but then you're getting into the "whole house" backup with subpanel, transfer switches, etc. You can install backup for your router as a small UPS, but then I also have cameras, doorbells, sensors, etc.
Well you can get small UPS for them too, but sure there are probably some points you can find around your corner of the envelope where PoE makes sense. That's not where many people are though.
> If you already have a house without Ethernet wiring, then opening up the walls just to run PoE makes no sense. But if you're building a new house or if you have pre-existing wiring (and a lot of newish houses do), then PoE is a no-brainer.
Not many new houses do at all because it costs money nobody really wants to pay. A builder will put some in if you ask but not off their own bat because they think it'll make the house worth more, because it won't. So unless some super nerd like your or I ask, no houses will be wired for ethernet. There was a brief window where wifi was non-existent or pretty slow and terrible where it got slightly popular, but that's long past.
If I was building a new house I would wire ethernet from a small server room/cupboard to just several places for wifi APs, plus ethernet and fiber from there to office. No PoE, they would all have USB-C power from same/adjacent wall plate as ethernet. And would probably look at solar+battery system with UPS capability, especially if I lived somewhere with shitty mains power. But even that is not appropriate for normies. They'd just buy a few mesh/repeater wifi things, not care that much about power going out once every few years, and be done with it.
Interesting that they made a new chip with BLE+BR/EDR again. all the chips after the original ESP32 were BLE only.
Hope this chip has good low power options so we can use it in Bluetooth audio workloads.
It would be good if this chip had good idle current comparable to other MCUs. I have used the ESP32S3 and it's idle current with the radio enabled, but not transmitting, is quite terrible.
My application needed both can bus and Bluetooth (though no wifi) so the S3 was one of the only options available. I'm sure the high current draw is because the wifi and ble share the same radio?
I assume their chips don't really exist until they're actually supported by ESP-IDF. The ESP32-C5 was announced in June 2022, received initial support in -IDF in August 2025, and more complete support in December. It seems to have only recently started getting third party dev boards.
I have great news for you: after several years of growing frustration with Espressif's inability to launch this chip properly in NA, I found a company called Wireless Tag that presumably felt the same way and just did it themselves:
I've now used this module in several projects. I love it. And I love (x3) the P4. It is amazingly powerful.
A lot of folks talk about the P4 not having radios as a problem; I personally think that it's an advantage. The assumption that every device is a wifi/BT device is baffling to me.
You'd have a very hard time convincing me to use anything but the WT0132P4-A1 at this point. They are cheaper than ESP32-S3-MINI-1U, too.
> A lot of folks talk about the P4 not having radios as a problem; I personally think that it's an advantage.
I believe, the problem is that there isn't a comparable chip with WiFi/BT (ignoring S3, because, you know, Xtensa), not that P4 itself doesn't have them.
I don't use these directly myself in any projects, so I'm citing hearsay... but from what I understand, Espressif officially recommends using an ESP32-C6 as a radio module with the P4. Wouldn't that cover it?
What I have seen directly is a lot of folks reacting negatively to the P4 because it doesn't have radios. They seem to be coming from a "what could it possibly be useful for if it can't [wifi/BT]". While it's easy to see this as a failure of imagination, it does seem true that a lot of folks equate the ESP32 line as what you use when you want to create an IoT device. While that's not wrong or necessarily bad, I've always felt like it's a weird way to pigeonhole an entire SoC family that might be self-limiting.
I guess it hit mass production and then suddenly recalled and is now in sample status again with “X” variant. I designed boards using esp32-p4 and deployed and then suddenly local supply of esp32-p4 went dry. Now waiting for the x variant to go mass production but you can by samples directly from espressif for 3.33$.
Realistically 2.4Ghz is far from "greatest backward compatibility" since there is a real benefit of running 5Ghz and 6Ghz only networks.
2.4Ghz makes sense because this tiny device does not need high speeds Wi-Fi connection, and deployment scenarios benefit from 2.4 GHz penetration more.
Honestly, I have very little interest in this module. I was a frequent S3 user who switched to the P4 last year when I realized that I could buy it in a WROOM-sized package:
The P4 is an amazing part, and the WT0132P4-A1 is cheap, highly available and easy to use. It has so much horsepower, and it's not encumbered by the mandatory wifi/BT stacks. It also has a genuinely superior capacitive touch solution compared to the S3.
For those of you who need radios, the recommended solution is to add a C3 as a coprocessor. I think this makes way more sense than bundling them, because it means you are free to use newer radio chips as they come out; this also makes the P4 somehow cheaper than the S3-MINI modules.
As for the S31, I just hope that they finally fixed the issues with ADC2.
Without being hands on, it's difficult to make a direct comparison. There's 2 processors according to CNX [0], and the HP core's instruction set might roughly be comparable to M55.
Don’t know the specifics of the Espressif RISC-V cores, but in general they can’t really compete on those aspects with ARM.
ARM is a much more mature platform, and the licensing scheme helps somewhat to keep really good physical implementations of the cores, since some advances get “distributed” through ARM itself.
Compute capabilities and power efficiency are very tied to physical implementations, which for the best part is happening behind closed doors.
I don't understand what possesses these folks to continue making 2.4ghz devices. I understand there are use cases for low bandwidth, high range. But surely we've passed the point where that is more desirable to most than lower latency and high throughput, right?
Is what you described a truth for all IoT devices? If I have los of my AP, why do I need 2.4Ghz? Even so, what SNR do you truly need for this low bandwidth application? Where is the engineering here?
I have a unique position of having a data set over 8000 APs with 40k unique devices. If you design properly, there is no need for 2.4 ever. 2.4Ghz congestion (with nearly no actual 802.11 traffic) is very high. To the point where the IoT folks are struggling.
Yes. And 2.4 lives and dies by that sword. What downsides might there be in areas where dozens of APs hear each other and 100s of clients hear each other?
It's an IoT device, not a laptop. It does not really need 5ghz to fulfill its purpose as an embedded CPU, and adding 5ghz likely would require making some room for it by removing other functionality.
Yes and in some uses cases it works against you. 2.4 is incredibly crowded without adding 802.11 to the mix. My IoT admins would have less complaints if they could take advantage of my small cell 5Ghz spectrum. This isn't 2005 with widely deployed asymmetrical wireless networks.
I use ESP32s extensively. I also use wifi extensively around the house - I have about 8 wifi access points around the property, with a ton of commercial IoT stuff powered on including sensors, lights, cameras, you name it, I got it. It's about as wifi-congested as any house can get.
So, I was measuring about 250KBit/s on an ESP32, and I decided to test everything that might increase the speed. I tried all the available antenna options for the ESP32 including many exotic antennas using the IPEX antenna connector variant of the ESP32, the stock ESP32 pcb antenna, and several chip antennas. A couple of them got up to 300KBit/s.
I also decided to see what happens when I power everything else off except for a single wifi router. So I did that, and I found that the stock ESP32 pcb antenna still got only 250KBit/s, and the other antennas measured exactly the same as they did before shutting everything down, too.
So, I don't know... 2.4ghz seems fine to me from my anecdotal tests.
Can't you just underpower the antenna on a 2.4 radio if you need networks that don't bleed into each other as badly? Unless it's an issue because of the tiny antennas that usually come on microcontrollers.
True for devices under your control. But think venues with large BYOD counts. Add in that all client devices generally transmit at full power. End result is an environment with not a lot of headroom in the 2.4 space.
2.4ghz isn't the only problem - even cell towers have problems with large amounts of devices. And "large BYOD" events are not a normal use case for wireless, and even 5GHz will have problems in those situations.
My 2.4ghz is basically all IOT these days. Things that matter are on 5 or 6 ghz. Busy moving the entire thing to be entirely firewalled off given how clean the separation is
Don't think you're ever going to reclaim that spectrum successfully. There must be billions of devices on it. Pretty much any other ghz number is a better bet
Not across all features, but certainly in specific ones. There are more advanced WiFi 6 chips, more advanced Bluetooth chips and faster MCUs. But they are all separate chips or companion ICs.
Although, I'd like to seem some non-paid blogger head-to-head reviews benchmarking instruction cycle efficiency per power of comparable Arm vs. ESP32 Xtensa LX6* and RISC-V parts.
* Metric crap tons of WROOM parts are still available and ancient ESP8266 probably too.
That native sdk and the vscode plugin are very professional. There is a bit of a learning curve to get into it, but once you do, it's very functional and the developers are super supportive. They have fixed bugs for me in days.
Boards like the ESP32-C6, almost 5 years old, are not supported in PlatformIO with Arduino libraries, because they refuse to update the Arduino core in some kind of stand-off with Espressif. This has been going on for years. There is a fork [1] that offers support but none of it makes back upstream.
As a hobbyist I've given up on PIO and moved to a barebones arduino-cli setup instead. Much lighter and less painful.
Still requires using rust compiled against their llm fork. 'espup' makes it easy if you're okay with using it.
Other than that it works pretty well. This is if you run ESP-IDF, with bare-metal rust it's either best thing ever or meh. Rust community seems to use stm32 and picos more.
> although it is not clear to me how much alive is the project
It's essentially dead. There are very few practical applications for it - modern embedded RTOSes are better suited to low-memory MMU-less parts, and SoCs with a MMU and more memory that can run a "real" Linux aren't very expensive.
you can run linux on riscv without an MMU. There is mainline support for Kendryte K210 chip, so it should be possible port to this chip provided you have enough PSRAM.
It’s not like creating a chip gives you unfettered access to it. You _can_ add 0-day flaws and backdoors, but these can be discovered, leaked, etc. Has there been any case of such a backdoor built in consumer chips like theses? I’m not talking about CIA ops like snowden described, that’s supply chain interception. I mean, has anybody ever found such a backdoor?
Well, that depends on what you count as a backdoor, but Espressif has had some questionable flaws:
- Early (ESP8622) MCUs had weak security, implementation flaws, and a host of issues that meant an attacker could hijack and maintain control of devices via OTA updates.
- Their chosen way to implement these systems makes them more vulnerable. They explicitly reduce hardware footprint by moving functionality from hardware to software.
- More recently there was some controversy about hidden commands in the BT chain, which were claimed to be debug functionality. Even if you take them at their word, that speaks volumes about their practices and procedures.
That’s the main problem with these kinds of backdoors, you can never really prove they exist because there’s reasonable alternative explanations since bugs do happen.
What I can tell you is that every single company I’ve worked which took security seriously (medical implants, critical safety industry) not only banned their use on our designs, they banned the presence of ESP32 based devices on our networks.
Except if you penetrate the market with modules that cost 5% of similar US made solutions, you start to win mindshare. At least some of those hobbyists start making a product, and sometimes the determination of whether a product is "safety critical" isn't agreed upon until after it's failed catastrophically.
I'm puzzled by Espressif's naming here. We had the ESP32-S3, so "S31" sounds like "S3, variant 1," but this part doesn't really look like a simple S3 variant. And then there's an ESP32-E22, but no E21 or even a plain E2 anywhere.
Edit: found an article explaining some of their naming logic, and said that the SoC naming will get its follow-up article, but sadly it never happened. https://developer.espressif.com/blog/2025/03/espressif-part-...
It reminds me a bit of the new STM32s (STM32MP2) which are actually 64 bit, but they kept the name STM32 because everyone knows it
Didn’t Intel also try to brand the 64bit x86 extensions as ia-32e initially? Seemed like wasting an opportunity to me.
(Disclaimer: I work at Intel but this was way before my tenure.)
It was because IA-64 was a completely different unrelated architecture that until AMD succeeded with K8 was "the plan" for both 64bit intel roadmap and the roadmap to kill off compatible vendors (AMD, VIA)
I stopped following the producer logic when Intel went from Pentium 4 to Pentium D
They claim that the chip has an "MMU". But unfortunately this doesn't seem to be a true RISC-V MMU (according to the Sv32 specification) integrated into the CPU core itself, but just a peripheral designed for memory mapped SPI flash and PSRAM. So as far as I understand there is no true process isolation with page faults and dynamic paging.
That’s a shame, it’d be a cool and, afaik, unique feature for this niche.
Maybe Espressif will notice that there are no RV32 chips with MMU so far (at least to my knowledge); we only have 32 bit MCUs or then only 64 bits for the CPUs. Something like Cortex-A7 is missing.
The upcoming Baochip is an RV32 chip with an MMU, I believe.
https://www.bunniestudios.com/blog/2026/baochip-1x-a-mostly-...
Edit - Oops GeorgeHahn beat me to it
There’s one incoming, https://baochip.github.io/baochip-1x/ It would be great to see more.
Baochip looks very interesting, and I highly respect bunnie's work, but I can't realistically say Baochip is a viable option for me, an unprofessional tinkerer.
Does anyone know what CPU this uses? Is it their own first party design?
Not sure I understand your question, but the ESP32-S3[1] is the "CPU" here.
> Not sure I understand your question
I'm not sure why you are not sure - S3 was using Cadence's Xtensa 32-bit LX7 dual-core microprocessor, but the article on S31 only mentions "dual core" without too much detail.
That's the SoC. The CPU is a small part of it. For example they could be using an open source design like the CVA6, or a commercial design from someone like Andes.
Espressif has a designed-in-house RISC-V CPU, so far as I know.
ESP32-S31 (very different from the S3)
That's literally and exactly what I said.
To be fair to GP, I too was confused by your use of brackets here.
I wasn't trying to be obtuse.
Formal grammar / technical documentation style guides consistently define:
[ ... ] = optional
{ ... } = repetition
| = alternatives
Hacker news isn't a formal grammar specification though. People use [1] for references here too (which you could easily have forgotten).
I believe this is the first ESP to gain Ethernet capability?
I totally wish that a board would come with PoE…
Because as it is right now, powering a fleet of those with USB power supplies is annoying as fsck…
Nah, ESP32's have had ethernet capability for a while and ESP-IDF supports it well. I've been using one I built for 5+ years now. Unfortunately RMII (ethernet phy) interface takes up a lot of the GPIO pins. This part looks like it'll remedy that issue.
There's two ESP32 boards that have been around for a while with PoE:
- https://www.tme.com/us/en-us/details/esp32-poe/development-k... - https://wesp32.com/
I'm more hopeful for single-pair ethernet to gain momentum though! Deterministic, faster than CANBUS, single pair, with power delivery:
https://www.hackster.io/rahulkhanna/sustainable-real-time-la...
Waiting for my ManT1S:
https://www.crowdsupply.com/silicognition/mant1s
I really wish there was a camera option. You’d have made wired doorbell cameras possible without a retrofit.
I’d buy in a heartbeat
> I'm more hopeful for single-pair ethernet to gain momentum though!
I keep looking for a reasonably priced 10baseT to 10Base-T1L bridge... everything commercial seems too expensive (for me) and the two hobby designs [1] [2] I've seen are not orderable :(
But I'm seeing more commercial options lately, so that's hopeful.
[1] http://robruark.com/projects/10BASE-T1L/10BASE-T1L.html
[2] https://matthewtran.dev/2024/08/10base-t1l-converter/
The ManT1S linked by a sibling has a bridge. Still not cheap, but probably better than most commercial ones.
any reason you won't send #2 to a pcbfab? include assembly if that's an issue.
SPE with multidrop and PoDL would be awesome ! They are working on that and it will be everywhere.
Multidrop SPE isn't going to outperform newer CAN versions though. Somewhere in the sub-100Mb/s (e.g. 10-20Mb/s range) is the practical maximum speed of a multidrop bus at useful lengths, and that essentially applies equally to CAN or SPE. The only way to really get faster in a "multidrop-like" sense is with logically loop-like systems like ethercat and Fibre Channel where each network segment is point-to-point and the nodes are responsible for the routing.
Are the newer CAN versions single pair with power delivery? Those are the real sweet spots of SPE.
This would be great indeed.
On that note, why does the PoE capability often add such a big proportion of the price of various items? Is the technology really costly for some reason, or is it just more there's fairly low demand and people are still willing to pay?
PoE is not obvious to implement (take it from someone who has done it with a fair share of mistakes), uses more expensive components that normal ethernet, takes up more space on the board, makes passing emissions certification more complex, and is more prone to mistakes that ruin boards in the future, causing support/warranty issues. In other words, a bag of worms: not impossible to handle, but something you would rather avoid if possible.
And what would a better alternative look like ?
I wouldn't call it "better", but the least-effort path among hobbyists and low end gear is often 12v or 24v sent over a pair with Gnd and a forgiving voltage regulator on the other end.
There is none, I never said PoE is "bad": it's a very good solution, it's just difficult to implement.
A full-module add-on in this power class is about $7 at 1,000 unit scale [0]. It would be around $3 with your own custom PCB design in terms of BoM addon at scale. That’s power only. Add another dollar or two for 10/100 PHY.
The trick is as others have said in what adding it to your design does in terms of complicating compliance design.
[0] https://www.digikey.com/en/products/detail/silvertel/AG9705-...
PoE power supplies need to be isolated (except in rare exceptions) and handle much higher voltages than common USB-C or wall wart power supplies.
They have to use a transformer and a more complex control strategy, not a simple buck regulator with an inductor. PoE inputs need to tolerate voltages several times higher than the highest USB-C voltages, so more expensive parts are used everywhere.
Any Ethernet (well, any RJ45 you expect in a home/office) has to have at least 1500V isolation from the RJ45 wire to anything metal that can be touched or is a connector on the device. A PoE-only device with no electrical connectors besides the RJ45 can just use a very cheap RJ45 port with integrated magnetics and PoE allowance (tiny bit bigger wires and a center pin exposed, less than 50ct more than the cheapest RJ45 with integrated magnetics) and a cheap buck from 40~80V to e.g. 5V.
Oh, and a cheap bridge rectifier and some signaling resistors to take care of input polarity and signal to the source that we in fact want the approximately 50V that could hurt a device not made for it.
> cheap buck from 40~80V to e.g. 5V.
That’s not a cheap buck lol. Order of magnitude more expensive then 12v not even mentioning capacitors that can withstand 80v is $$$ and your derating goes to shit
It sounds like the PoE spec was designed before the arrival of “IoT” type things like the esp32, raspberry pi’s, etc.
How much of the complexity is a “fundamental electrical engineering problem” and how much of it is just a spec written to solve a different set of problems?
Ethernet is already one of the most expensive standards because you need magnetics for isolation. Adding power on top of that is genuinely expensive.
Whenever you combine two things into one, the complexity and cost go up considerably. A regular coffee machine is pretty cheap. Add high pressure so it can make espresso and it gets considerably more expensive. Add milk so it can make cappuccino, again more complex and expensive. The same holds for electronics. Isolating power when it's alone is fairly straightforward. It gets considerably more tricky and hence more expensive the moment you want to place any kind of a meaningful data signal in its vicinity.
I’m sure the other commenters are right, but I’m guessing market segmentation may play a role here too.
The original ESP32 has Ethernet as well, I believe in the form of RMII. Then it has been removed from the chip, never specified the reason.
Can't you run a 5V supply from where your router is all the way to every god damn device in your house, and then pretend the wifi is also going through it? If you just want it to be inconvenient, there's no reason to let a lack of PoE stop you!
> Because as it is right now, powering a fleet of those with USB power supplies is annoying as fsck…
Therefore, wifi is more convenient than ethernet.
You don't need long cables, just a local power source.
> You don't need long cables, just a local power source
Which means batteries that have to be replaced and maintained or cables... So ethernet with PoE or even better SPE (single pair Ethernet) with PoDL (power over data lines which is PoE for SPE) is the best from my point of view
Well, yes, but then you need to be "in range" of PoE switch and drag the ethernet cable from it vs the nearby socket. Still, nice to have options
I mean, if I just look at my house. There is just one ethernet outlet, but many power sockets. If I want to connect devices all over my house, the best way is to use wifi and usb power adapters. Not ethernet.
Both solutions require 1 cable per device, but the first solution would require only short and thin cables, and the second solution would require very long cables which I don't know even how to do properly without milling my walls.
Yep. Mains electricity is ubiquitous, highly interoperable, very reliable, very high power available per drop, can be outdoor capable, common standards, understandable by users, requiring no active components, with many on-call experts available who can come to fix problems or extend/alter connectivity. Mains power wall plates with inbuilt USB power outlets are even available at quite small cost if the look of the bigger plug and wiring is not appealing.
PoE is much fewer of those things. Difficult to recommend it these days with wifi being fast and reliable and so widely used. Certainly not for average residential user.
That's half the equation. The other half is the reliability and security of wifi, which is less than that of ethernet for people without physical access to my wall innards
Reliability of wifi is not as good I guess, although these days it is extremely good for decent devices. For poor quality devices, I have also heard of PoE routers blowing ports and devices that don't work properly.
Is security of wifi an actual practical concern? I've not heard of it since WPA2.
For average residential user, even most hobbyist / enthusiast, I doubt those things will matter. Almost everybody who wants extremely fast reliable wired connectivity will be much better off using fiber, and using wifi for cameras and automation and streaming and other such things. Getting power to where you need it is not the difficult part, especially if you're pulling wires anyway, which is why PoE has always been fairly niche.
Reliability and security of wifi isn't good when jamming of it is so easy and available. It's a lot harder to jam ethernet at a distance.
Pretty niche requirement for personal user though. Protection against eavesdropping is the main thing required, and PoE is actually much worse for that than WiFi is you have any drops in less secured ares (e.g., outdoor cameras).
I can see that. I have security devices on my network (e.g. a camera), so I might come at this with a different perspective (since it's not uncommon for burglars to jam wifi).
On the other hand, _all_ the WiFi devices that I had at some point fell off the network, at least once. Including doorbells and cameras. While PoE devices just work.
Another point is that mains power in my area can go down periodically. My PoE switch is powered by a Li-Ion UPS and can provide power for about a day.
> On the other hand, _all_ the WiFi devices that I had at some point fell off the network, at least once. Including doorbells and cameras. While PoE devices just work.
I've not had that in a decade, and only for really shitty devices. I've also had crappy PoE devices stop working, ports blow. Too much effort to be worth the bother for me nowadays. If I had to bet my life sure I'd probably use wired ethernet. But if I had to bet my life I wouldn't be using PoE for power either.
UPS is entirely possible to do on residential mains circuits.
> I've not had that in a decade, and only for really shitty devices. I've also had crappy PoE devices stop working, ports blow.
Every ESP32-based WiFi device _will_ at some point get stuck in the disconnected state. It's almost an ironclad guarantee.
> UPS is entirely possible to do on residential mains circuits.
Sure, but then you're getting into the "whole house" backup with subpanel, transfer switches, etc. You can install backup for your router as a small UPS, but then I also have cameras, doorbells, sensors, etc.
If you already have a house without Ethernet wiring, then opening up the walls just to run PoE makes no sense. But if you're building a new house or if you have pre-existing wiring (and a lot of newish houses do), then PoE is a no-brainer.
> Every ESP32-based WiFi device _will_ at some point get stuck in the disconnected state. It's almost an ironclad guarantee.
See earlier note about crappy devices.
> Sure, but then you're getting into the "whole house" backup with subpanel, transfer switches, etc. You can install backup for your router as a small UPS, but then I also have cameras, doorbells, sensors, etc.
Well you can get small UPS for them too, but sure there are probably some points you can find around your corner of the envelope where PoE makes sense. That's not where many people are though.
> If you already have a house without Ethernet wiring, then opening up the walls just to run PoE makes no sense. But if you're building a new house or if you have pre-existing wiring (and a lot of newish houses do), then PoE is a no-brainer.
Not many new houses do at all because it costs money nobody really wants to pay. A builder will put some in if you ask but not off their own bat because they think it'll make the house worth more, because it won't. So unless some super nerd like your or I ask, no houses will be wired for ethernet. There was a brief window where wifi was non-existent or pretty slow and terrible where it got slightly popular, but that's long past.
If I was building a new house I would wire ethernet from a small server room/cupboard to just several places for wifi APs, plus ethernet and fiber from there to office. No PoE, they would all have USB-C power from same/adjacent wall plate as ethernet. And would probably look at solar+battery system with UPS capability, especially if I lived somewhere with shitty mains power. But even that is not appropriate for normies. They'd just buy a few mesh/repeater wifi things, not care that much about power going out once every few years, and be done with it.
> My PoE switch is powered by a Li-Ion UPS and can provide power for about a day.
Same - and i can "remote yank" the power, thus restart the devices without lifting a finger (much).
Esp32 's wifi is only 2.4ghz though.
No. It’s there already. I used Ethernet on esp32-p4 and it nicely hovers around 90-100 mbps with lan8720 chip.
M5stack has PoE offerings
Interesting that they made a new chip with BLE+BR/EDR again. all the chips after the original ESP32 were BLE only. Hope this chip has good low power options so we can use it in Bluetooth audio workloads.
It supports LE Audio, might help getting that tech some traction
> high-speed 250 MHz 8-bit DDR PSRAM with concurrent flash and PSRAM access
This is perhaps lost in the noise but IMO a large deal. PSRAM starting to get serious bandwidth.
For reference, the 4-bit PSRAM interface on the ESP32-S3 normally runs at 80 MHz (maximum 120 MHz) and shares bandwidth with the external flash.
I wonder if it will be possible to (ab)use the faster PSRAM interface on the ESP32-S31 as a general purpose 8-bit parallel interface, eg. for ADCs...
It would be good if this chip had good idle current comparable to other MCUs. I have used the ESP32S3 and it's idle current with the radio enabled, but not transmitting, is quite terrible.
My application needed both can bus and Bluetooth (though no wifi) so the S3 was one of the only options available. I'm sure the high current draw is because the wifi and ble share the same radio?
I had the same theory, but IIRC the H2 isn't much better with radio on.
I don’t trust Espressif’s releases, I am still waiting for ESP32-P4 to hit distributors. It is now more than 2 years and 3rd chip revision
I assume their chips don't really exist until they're actually supported by ESP-IDF. The ESP32-C5 was announced in June 2022, received initial support in -IDF in August 2025, and more complete support in December. It seems to have only recently started getting third party dev boards.
I have great news for you: after several years of growing frustration with Espressif's inability to launch this chip properly in NA, I found a company called Wireless Tag that presumably felt the same way and just did it themselves:
https://en.wireless-tag.com/product-item-56.html
I've now used this module in several projects. I love it. And I love (x3) the P4. It is amazingly powerful.
A lot of folks talk about the P4 not having radios as a problem; I personally think that it's an advantage. The assumption that every device is a wifi/BT device is baffling to me.
You'd have a very hard time convincing me to use anything but the WT0132P4-A1 at this point. They are cheaper than ESP32-S3-MINI-1U, too.
> A lot of folks talk about the P4 not having radios as a problem; I personally think that it's an advantage.
I believe, the problem is that there isn't a comparable chip with WiFi/BT (ignoring S3, because, you know, Xtensa), not that P4 itself doesn't have them.
I don't use these directly myself in any projects, so I'm citing hearsay... but from what I understand, Espressif officially recommends using an ESP32-C6 as a radio module with the P4. Wouldn't that cover it?
What I have seen directly is a lot of folks reacting negatively to the P4 because it doesn't have radios. They seem to be coming from a "what could it possibly be useful for if it can't [wifi/BT]". While it's easy to see this as a failure of imagination, it does seem true that a lot of folks equate the ESP32 line as what you use when you want to create an IoT device. While that's not wrong or necessarily bad, I've always felt like it's a weird way to pigeonhole an entire SoC family that might be self-limiting.
Can also be ordered on JLCPCB in a custom PCB: https://www.lcsc.com/product-detail/C22387510.html?s_z=n_ESP...
I guess it hit mass production and then suddenly recalled and is now in sample status again with “X” variant. I designed boards using esp32-p4 and deployed and then suddenly local supply of esp32-p4 went dry. Now waiting for the x variant to go mass production but you can by samples directly from espressif for 3.33$.
HN title entropy record?
Only a few characters away from my password!
Love ESP boards, and with Raspberry pi pricing though the roof, I’m hoping more will discover the love of getting the job done on a 10mm2 package.
I suspect a lot of the things people are using RPi for are better served by things like this (and virtualisation for the heavier end)
Pardon for off topic. The designer in me hates that they used AI for every single asset in this release post, looks so amateurish.
I hope this one has multiple radios so you can actually use BT/Wifi/Thread simultaneously.
Argh…Wifi 6 , but 2.4ghz.
Adding 2 frequency ranges is more expensive. If you're going to choose just one, you should choose the one with the greatest backward compatibility.
Realistically 2.4Ghz is far from "greatest backward compatibility" since there is a real benefit of running 5Ghz and 6Ghz only networks.
2.4Ghz makes sense because this tiny device does not need high speeds Wi-Fi connection, and deployment scenarios benefit from 2.4 GHz penetration more.
There is an ESP-C5 (https://www.espressif.com/en/products/socs/esp32-c5) that supports 2.4 and 5 GHz dual-band WiFi. And unlike the ESP32-S31 you can buy it today.
Oh neat. Zigbee support.
I wonder if I at some point can create low power devices with EspHome for home assistant. I assume this should use less power than connecting to wifi?
The C6 and the H2 already support ZigBee. Their SDK has a thin layer on top of zboss.
You already can with nRF52 boards. Presumably they'll add ESP32 support soon too.
https://esphome.io/components/zigbee/
Perfect timing. I just started planning to build a DIY smartwatch and was looking into the S3. Having native zigbee support could be nice.
The S3 (and other Espressif chips) are pretty power-hungry. May want to keep looking for a smartwatch application.
S3 was just for me to do an initial prototype. Longer term was going to try with the C3, though I'm open to suggestions :)
You could consider similar devices and what they have used. Another angle is to look at ULPMark results: https://www.eembc.org/ulpmark/
Honestly, I have very little interest in this module. I was a frequent S3 user who switched to the P4 last year when I realized that I could buy it in a WROOM-sized package:
https://en.wireless-tag.com/product-item-56.html
The P4 is an amazing part, and the WT0132P4-A1 is cheap, highly available and easy to use. It has so much horsepower, and it's not encumbered by the mandatory wifi/BT stacks. It also has a genuinely superior capacitive touch solution compared to the S3.
For those of you who need radios, the recommended solution is to add a C3 as a coprocessor. I think this makes way more sense than bundling them, because it means you are free to use newer radio chips as they come out; this also makes the P4 somehow cheaper than the S3-MINI modules.
As for the S31, I just hope that they finally fixed the issues with ADC2.
How do Espressif’s RISC-V cores compare to existing ARM or RISC-V options in terms of power efficiency (computational power / electrical power)?
Without being hands on, it's difficult to make a direct comparison. There's 2 processors according to CNX [0], and the HP core's instruction set might roughly be comparable to M55.
[0] https://www.cnx-software.com/2026/03/24/esp32-s31-dual-core-...
Don’t know the specifics of the Espressif RISC-V cores, but in general they can’t really compete on those aspects with ARM.
ARM is a much more mature platform, and the licensing scheme helps somewhat to keep really good physical implementations of the cores, since some advances get “distributed” through ARM itself.
Compute capabilities and power efficiency are very tied to physical implementations, which for the best part is happening behind closed doors.
Are there any US vendors with wifi/BLE-integrated MCUs -- a single package that does it all?
It has become limited. Some have WiFi, some have Bluetooth but rarely both. There is the SiWx917M (https://www.silabs.com/wireless/wi-fi/siwx917-wireless-socs) by SiliconLabs though.
If we include western companies you get the NXP RW612 (https://www.nxp.com/products/wireless-connectivity/wi-fi-plu...) which is dutch.
Roughly how much do you think this costs?
Given their history, I would guess <$6 a piece for a dev board, <$2 for the chip at scale.
I don't understand what possesses these folks to continue making 2.4ghz devices. I understand there are use cases for low bandwidth, high range. But surely we've passed the point where that is more desirable to most than lower latency and high throughput, right?
> I understand there are use cases for low bandwidth, high range.
Use cases like IoT? The very thing this is for?
Is what you described a truth for all IoT devices? If I have los of my AP, why do I need 2.4Ghz? Even so, what SNR do you truly need for this low bandwidth application? Where is the engineering here?
I have a unique position of having a data set over 8000 APs with 40k unique devices. If you design properly, there is no need for 2.4 ever. 2.4Ghz congestion (with nearly no actual 802.11 traffic) is very high. To the point where the IoT folks are struggling.
2.4 GHz has the advantage of it passing through obstacles easier. The higher the frequency the more easily it gets blocked.
Yes. And 2.4 lives and dies by that sword. What downsides might there be in areas where dozens of APs hear each other and 100s of clients hear each other?
It's an IoT device, not a laptop. It does not really need 5ghz to fulfill its purpose as an embedded CPU, and adding 5ghz likely would require making some room for it by removing other functionality.
Yes and in some uses cases it works against you. 2.4 is incredibly crowded without adding 802.11 to the mix. My IoT admins would have less complaints if they could take advantage of my small cell 5Ghz spectrum. This isn't 2005 with widely deployed asymmetrical wireless networks.
I use ESP32s extensively. I also use wifi extensively around the house - I have about 8 wifi access points around the property, with a ton of commercial IoT stuff powered on including sensors, lights, cameras, you name it, I got it. It's about as wifi-congested as any house can get.
So, I was measuring about 250KBit/s on an ESP32, and I decided to test everything that might increase the speed. I tried all the available antenna options for the ESP32 including many exotic antennas using the IPEX antenna connector variant of the ESP32, the stock ESP32 pcb antenna, and several chip antennas. A couple of them got up to 300KBit/s.
I also decided to see what happens when I power everything else off except for a single wifi router. So I did that, and I found that the stock ESP32 pcb antenna still got only 250KBit/s, and the other antennas measured exactly the same as they did before shutting everything down, too.
So, I don't know... 2.4ghz seems fine to me from my anecdotal tests.
Can't you just underpower the antenna on a 2.4 radio if you need networks that don't bleed into each other as badly? Unless it's an issue because of the tiny antennas that usually come on microcontrollers.
True for devices under your control. But think venues with large BYOD counts. Add in that all client devices generally transmit at full power. End result is an environment with not a lot of headroom in the 2.4 space.
2.4ghz isn't the only problem - even cell towers have problems with large amounts of devices. And "large BYOD" events are not a normal use case for wireless, and even 5GHz will have problems in those situations.
My 2.4ghz is basically all IOT these days. Things that matter are on 5 or 6 ghz. Busy moving the entire thing to be entirely firewalled off given how clean the separation is
>My 2.4ghz is basically all IOT these days.
Yup. And it's exactly why some of my IoT admins are struggling. There is only so much spectrum to go around.
Don't think you're ever going to reclaim that spectrum successfully. There must be billions of devices on it. Pretty much any other ghz number is a better bet
Is there something that match those elsewhere ?
Not across all features, but certainly in specific ones. There are more advanced WiFi 6 chips, more advanced Bluetooth chips and faster MCUs. But they are all separate chips or companion ICs.
Soon espressif will add TPU to their chips.
Hopefully it will be just added to https://github.com/espressif/esp-nn on software side.
Interesting.
Although, I'd like to seem some non-paid blogger head-to-head reviews benchmarking instruction cycle efficiency per power of comparable Arm vs. ESP32 Xtensa LX6* and RISC-V parts.
* Metric crap tons of WROOM parts are still available and ancient ESP8266 probably too.
The ESP32 boards I own have bad support and are a bit of a hit and miss. (arduino nano esp32) Did this get better? Or is the support still messy?
That native sdk and the vscode plugin are very professional. There is a bit of a learning curve to get into it, but once you do, it's very functional and the developers are super supportive. They have fixed bugs for me in days.
Arduino nano are made by arduino using Espressif chips, and Arduino IDE support is indeed hit and miss.
ESP-IDF, the official C SDK, is a bit more work, and there is drama around platform-io, but it’s significantly more stable.
> there is drama around platform-io
What do you mean ?
Boards like the ESP32-C6, almost 5 years old, are not supported in PlatformIO with Arduino libraries, because they refuse to update the Arduino core in some kind of stand-off with Espressif. This has been going on for years. There is a fork [1] that offers support but none of it makes back upstream.
As a hobbyist I've given up on PIO and moved to a barebones arduino-cli setup instead. Much lighter and less painful.
[1] https://github.com/pioarduino/platform-espressif32
Don't use the Arduino framework, use ESP-IDF or Rust.
For those using PlatformIO, the folks at pioarduino[0] are doing a great job keeping up with Arduino Core 3.x support.
[0]: https://github.com/pioarduino/platform-espressif32how's Rust on the xtensa cores ?
Still requires using rust compiled against their llm fork. 'espup' makes it easy if you're okay with using it.
Other than that it works pretty well. This is if you run ESP-IDF, with bare-metal rust it's either best thing ever or meh. Rust community seems to use stm32 and picos more.
I've found that it does have some issues with the number 4096 though...
POC: https://github.com/astolarz/piper-cannot-select
What do you mean by that? bad support for what?
Does it run Linux?
No, missing a MMU.
There is μClinux [1] although it is not clear to me how much alive is the project
I wish I could run DiscoBSD/RetroBSD [2] on an ESP32, I like the idea of running on a MCU something that was originally meant for a PDP/11 (2.11 BSD)
[1] https://en.wikipedia.org/wiki/%CE%9CClinux
[2] https://github.com/chettrick/discobsd
> although it is not clear to me how much alive is the project
It's essentially dead. There are very few practical applications for it - modern embedded RTOSes are better suited to low-memory MMU-less parts, and SoCs with a MMU and more memory that can run a "real" Linux aren't very expensive.
you can run linux on riscv without an MMU. There is mainline support for Kendryte K210 chip, so it should be possible port to this chip provided you have enough PSRAM.
why would you do that? (unless for the fun of it)
Just to get an idea of its capabilities.
Imagine installing Claude Code in it with full root access. Just by asking a few things, you can have a semi-broken ESP32 doing stuff.
Since the Snowden leaks in 2013, it just doesn't make sense that *any* foreign customers would put US technology inside their firewall. But they do.
It shocks me even more that any Western customer would do the same with network-connected Chinese chips. But we do.
The Espressif chips are truly incredible value, but what are we doing here?
Is there any doubt that these don't represent a major attack surface if a conflict were to heat up?
If you had network-connected chips of your own design inside every household of your adversary, what could you do with that?
It’s not like creating a chip gives you unfettered access to it. You _can_ add 0-day flaws and backdoors, but these can be discovered, leaked, etc. Has there been any case of such a backdoor built in consumer chips like theses? I’m not talking about CIA ops like snowden described, that’s supply chain interception. I mean, has anybody ever found such a backdoor?
Well, that depends on what you count as a backdoor, but Espressif has had some questionable flaws:
- Early (ESP8622) MCUs had weak security, implementation flaws, and a host of issues that meant an attacker could hijack and maintain control of devices via OTA updates.
- Their chosen way to implement these systems makes them more vulnerable. They explicitly reduce hardware footprint by moving functionality from hardware to software.
- More recently there was some controversy about hidden commands in the BT chain, which were claimed to be debug functionality. Even if you take them at their word, that speaks volumes about their practices and procedures.
That’s the main problem with these kinds of backdoors, you can never really prove they exist because there’s reasonable alternative explanations since bugs do happen.
What I can tell you is that every single company I’ve worked which took security seriously (medical implants, critical safety industry) not only banned their use on our designs, they banned the presence of ESP32 based devices on our networks.
You can hide malicious intent, so the repeated negligence patterns you’re pointing out make a better signal. Smart. Thx for the perspective
Obviously... They are not made for safety critical systems. It's for hobbyists.
These parts are in a massive number of retail smart switches 3d printers and iOT devices.
They are definitely beyond a hobby device.
They're made well, designed well and the libraries are some of the best in class.
My concern is purely on risk.
What would any responsible state security agency spend to have devices behind every single firewall of an adversary?
Except if you penetrate the market with modules that cost 5% of similar US made solutions, you start to win mindshare. At least some of those hobbyists start making a product, and sometimes the determination of whether a product is "safety critical" isn't agreed upon until after it's failed catastrophically.