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• Crowd Supply pre-campaign page live

  Patrick Van Oosterwijck • 09/05/2018 at 00:17 • 0 comments

  The wESP32 Crowd Supply pre-campaign page is now live!

  Check it out and sign up if you want to be notified when the campaign goes live!  There will be some early bird specials so signing up may land you a special deal. :)
  

• Coming to Crowd Supply!

  Patrick Van Oosterwijck • 08/31/2018 at 18:43 • 0 comments

  The wESP32 is coming to Crowd Supply!  After seeing how successful our #LiFePO4wered/Pi+ campaign was, it made sense to repeat the same thing for the wESP32.  I hope to have the campaign up very soon now so you can start ordering!
  

  I've been very busy the past week with ordering boards, ordering components, and coming up with marketing materials.  A campaign video is in the works, and we need demos to show off some cool stuff you can do with the wESP32.  One simple idea was to make a "remote status display" you can send messages to:

  You'd probably want a bigger screen for the real deal, but is conveys the idea. :)

  @martinschki had a good question in the comments: "How much heat do they emit under a low power application?"  I've been doing tests and taking thermal pictures at high load, but I never thought of doing it for low loads!  And in applications such as his where things get built into a wall this is important.  So here's a thermal image under low load, running the demo shown above:

  So it looks like the hottest thing on the board is the Ethernet phy chip.  At 51°C I don't expect any problems for having it in a wall.  But if you're going to use this to build an environmental sensor, you definitely need to keep this heat in mind when you design your device or your readings will be way off!
  

• Final performance checks

  Patrick Van Oosterwijck • 08/21/2018 at 18:19 • 0 comments

  I had left off my data performance testing last time wondering why the iperf UDP data rate was so low.  Well, @aenertia on Twitter gave me a hint: you need to specify the amount of bandwidth you want to test on the client side, otherwise the UDP test defaults to 1 Mbit/s!  So, just an average case of operator error. :)  The iperf on ESP32 example code is too simple and doesn't provide / need this option, and I haven't played enough with this kind of stuff before to know things like that.
  

  Here are the results for UDP when the wESP32 is the client (outgoing traffic):

  Around 70 Mbit /s, nice!

  So to test server, I used the following command on the client:

  iperf -c 10.10.16.44 -i 3 -t 60 -u -b 100m

   This sets the target bendwidth to 100 MBit/s.
  

  Here are the results for UDP when the wESP32 is the server (incoming traffic):

  Wow, >90 Mbit/s!  That's close to the theoretical maximum!

  Now I'm pretty sure that from the moment the ESP32 would start to do anything with this data other than throw it away, the data rate would go down, but it's still nice to see that the Ethernet data system as implemented on the wESP32 performs very well.

  One last thing left on my list to validate the design was to test power performance when the 5V power option is selected by bridging the solder jumper.  As mentioned before, the whole power system is optimized for 12V power, and the 5V option was a little bit of an afterthought but it could be useful to many people.  So how does it do?

  In my first test I was really pushing it:

  Trying to push >2A through a power path that was designed for 1A: not a good idea.  That poor diode was frying, but it lived.  So, intermittent 10W may be possible at 5V, but don't run it like this continuously.

  Here's a more moderate test:

  That's better.  At 6W output (1.2A), the diode temperature isn't so bad.  Still, when running at 5V, your continuous average load should probably be kept below 5W.

  These results are fine though.  If you need high power, use 12V.  It keeps the currents much more reasonable.  If you really need high power at 5V, add your own buck converter.  The on-board option for 5V will likely still be very useful for the majority of people who need 5V in their system though.  5V sensors, keypads, displays, etc. usually don't need that much power.
  

• More data performance

  Patrick Van Oosterwijck • 08/19/2018 at 05:14 • 3 comments

  After I posted the previous log, I kept working on trying to figure out the data rate figures, the worrying one being iperf performance when the wESP32 was the server, which was really poor.
  

  Taking a step back, the reason I was doing these tests in the first place was to validate the hardware.  Before I go to production, I need to have confidence that the design is sound, and in the case of this test, that there aren't any circuit or layout issues that are making the signal path performance poor, such as interference from the PoE power system or impedance mismatches causing reflections and affecting the signal to noise ratio.  Such issues would result in high packet loss, making retransmission necessary, which in turn is observed by poor data rates.

  So from the previous tests, it looked like the outgoing signal path had been validated as working well (iperf client), but the incoming signal path was suspect (iperf server).  So I started looking at the layout to see if there was anything obviously different between the incoming and outgoing signal paths.  Not really, both the TXP/TXN and RXP/RXN were laid out as impedance matched differential pairs.  In the picture below, you can see them as the 4 fatter traces under the "Wired ESP32 with PoE" writing:

  While I was perusing the LAN8720A phy datasheet to see which pair was suspect, I looked at the "Architectural Overview" block diagram on page 5, and I noticed something I had forgotten: that this chip implements "Auto-MDIX", a feature that automatically switches the TXP/TXN and RXP/RXN pairs as required to work correctly with either straight or crossover Ethernet cables.

  This gave me an idea: if I used a crossover cable, the incoming and outgoing data would switch on which differential pairs they were travelling, and the phy would internally switch them back so things would still work.  If the problem moved from incoming to outgoing when I did this, then I'd know one of the data pairs was performing poorly.  If nothing changed, and the performance on the outgoing data test was still good, I'd know both data pairs were performing well.

  After locating a crossover cable, I ran the test, and the results were identical to the ones from the test with the straight cable.  This means both data pairs are performing equally well and the data path is sound!  Yay! :)

  So, the question remained: why was the iperf server test working so poorly?  Even though I had pretty much validated the hardware, this still bugged me so I kept trying to see if I could figure out the issue.  I decided to play with some of the settings offered in 'make menuconfig'.  In the process of doing this, at some point I got the client performance to >80 Mbit/s, but the server performance remained poor.  Eventually I did find something that made the TCP test work: the option "CONFIG_EMAC_L2_TO_L3_RX_BUF_MODE".

  The docs explain that "when Ethernet MAC doesn’t have any unused buffers left, it will drop incoming packets (flow control may help with this problem, to some extent)".  Still, the docs recommend to keep this turned off if unsure, because it involves copying data instead of passing pointers, which decreases performance.  Still, the iperf test was apparently running into the problem that the MAC didn't have buffers left, because turning it on made a big difference.  Here are the results of the iperf client test with this config:

  And here are the results of the server test, which now performs well:

  That's when testing with TCP.  Oddly, the UDP server test still performs very poorly: I only get around 1 Mbps.

  Obviously, this is some other configuration issue.  Since TCP was working well, I called it a day.

  Overall, I'm very happy with the performance of these first prototypes: the power output beats my expectations and the spec, the attainable data rate is very good and beats my expectations as well.  With these prototypes working as well...

  Read more »

• Data performance

  Patrick Van Oosterwijck • 08/17/2018 at 18:41 • 0 comments

  After confirming the PoE power subsystem performance, I wanted to make sure that the data path was sound as well.  To do this, I needed some performance test.  The ESP-IDF contains an iperf example for WiFi, but there isn't any for Ethernet.  So I decided to try and hack the Ethernet example and the WiFi iperf together.  It's messy and ugly, but eventually I got it to work.  Here are the test results:

  Around 63-64 Mbit/s, not too shabby for a little chip!  Of course I don't really have much to compare to.  Anyone have any numbers on how much speed can be expected from an Ethernet connected ESP32?

  The first test was in TCP mode.  Then I tried the same thing in UDP mode:

  Wow, more than 70 Mbit/s, even better!
  

  Then I decided to try the ESP32 as a server instead of client:

  Whaaa?  That's just weird, something seems wrong.  Anyone have any idea why this would happen?
  

• Initial test results

  Patrick Van Oosterwijck • 08/02/2018 at 03:16 • 1 comment

  Initial test results are in!

  I used my electronic load to see if the wESP32 prototypes would achieve my target of 12.95W output power to meet the 802.3at Type 1 PoE specification.  Here's my setup:

  Yes, you are seeing that correctly on the display of the electronic load: 13.5W!  What's more, I kept it running like this for a couple of hours and it was stable!  No over current or thermal shutdown.  And this is without any heat sink attached to the mounting hole!  I never expected I would get full target power without extra heat sinking.
  

  The hot spots are as expected the Si3404A PoE power converter chip and the secondary side Schottky rectifying diode.  The diode is hot, but it's within acceptable limits:

  The power chip is getting much hotter, not enough to trigger over temperature protection apparently, but too hot to run like this for a long time:

  Although it works, I would not recommend running at full power without any heat sinking.  So how much difference does connecting a heat sink to the mounting hole actually make?  Let's find out:

  It may be noted that I'm not trying very hard here to provide an optimal heat sink.  I'm just using a flat piece of aluminum with a stand-off screwed into it, screwed to the mounting hole.  No thermal grease is used.

  As you can see, I decided to really push it and bumped power up to 14.7W.  This was stable with the extra heat sinking.  Of course, the diode got a little hotter now:

  Still perfectly acceptable.  The power chip on the other hand is cooler now, because the heat sink is doing its job pulling heat away from the chip:

  I decided that to compare apples to apples, I better reduce the output load to the same 13.5W as before so I could see how much difference in temperature the heat sink actually makes:

  That's 25°C cooler, at an acceptable temperature while running at a load that's higher than demanded by the spec.  I call that good enough. :)

  An interesting detail in the latter thermal images: the resolution is good enough to see a couple more small hot spots: one by current sense resistor R20 and one by resistor R10 of the RCD clamp.  Both are normal and expected: the current sense resistor senses the current through the primary winding and will dissipate around 0.1W under high load, while the RCD clamp is there to dissipate energy from self-inductance of the primary flyback winding, to prevent this energy from resonating and producing large (noisy and potentially damaging) voltage spikes.
  

  It should be noted that in all these tests the actual load is a little higher than what I see on the electronic load display because the 3.3V buck converter, ESP32 and Ethernet Phy consume some power as well.  But I decided to ignore it for these tests since it's less than 0.5W or so.

  So how does the flyback converter's output power look?  How much noise is on it under various loads?  I had planned to show some scope traces, but I decided against it because they were very boring: just a flat line. :)  That's excellent!  Even under the highest load, the V+ power bus looks very clean.  I haven't had this design tested for EMI but if/when I do, it looks like it may be fine.

  Very happy with these results.  Next, I need to check what happens when 5V output is selected, and try to figure out what's wrong with the two prototypes that aren't fully functional, plus build some more prototypes for the people who are waiting to buy them for their own testing.
  

• Prototypes... built and tested!

  Patrick Van Oosterwijck • 07/28/2018 at 04:30 • 5 comments

  I found time to build four wESP32 prototypes yesterday!  Here are some shots taken during the (manual) assembly process.

  Stencil with board ready to be pasted:
  

  Boards with solder paste, ready for assembly:

  Most components placed:

  After reflow:

  All boards needed some touch up, my solder pasting was kinda messy with the frameless stencil and the old paste, so there was some bridging on the QFNs that needed to be fixed up.

  Then after I completed the assembly of the first prototype I plugged in the PoE Ethernet jack and immediately measured 11.4V on the V+ rail!  Yay, what a relief! :)  The PoE section seems to be immediately operational.  I had some trouble programming the ESP32 using the ESP32-Prog submodule though.  Switched to a different prototype I finished up, and on that one I could program the ESP32 right away!  So I loaded the ESP-IDF Ethernet example and plugged it in:
  

  Behold, blinking LEDs on the Ethernet jack and a sure sign of success! Checking the serial monitor, I could tell the device was successfully getting an IP address from DHCP as well. :)

  This is what has been verified to work so far on some of these prototypes:

  • PoE produces 11.4V on the V+ rail, and 5.1V when the 5V solder bridge is closed.
  • Buck converter produces 3.3V to power the ESP32 and Phy.
  • Ethernet Phy is operational and communicates with the ESP32, tested to the point of getting an IP address from DHCP.
  • ESP32-Prog submodule and on-board logic manages the EN and IO0 signal correctly to allow programming, serial monitoring and 50MHz EMAC clock to work correctly.

  I have two prototypes where all the above works, a third seems to work but for unknown reason it is not getting an IP address from DHCP, and on the fourth I can't seem to program the ESP32 yet.  Still work to do to get those going but it seems likely these are just assembly issues and not a problem with the design.  Let's hope.
  

  More testing is still needed to make sure the design is sound:

  • Check the power supplies and see how noisy they are, optimize snubbers and filters in the flyback stage to minimize noise and optimize the EMC.
  • Check how much power can be pulled from the PoE with and without a heat sink attached.  See if we get to 12.95W which is the target for 802.3af (802.3at Type 1).  I hope to get there with a heat sink, but expect a lower maximum when no heat sink is used.
  • Check how much power we can pull when the 5V option is selected.  I'm not expecting to reach 12.95W here, since the flyback is optimized for 12V.
  • Check if we have enough power and good enough signal with really long cables (does anyone know if there is a way to get a signal qualify figure from the phy?).
  • Check how much power is available from the 3.3V rail for the specification.

• ESP32-Prog prototype

  Patrick Van Oosterwijck • 07/25/2018 at 23:27 • 0 comments

  The last three months have been absolutely crazy.  Between vacation, selling a house, buying a house, remodelling 4 bedrooms, moving, visits by family and friends, an audit, and getting the #LiFePO4wered/Pi+ Crowd Supply campaign going, I've had very little time to work on the wESP32 unfortunately.

  So I'm relieved that I finally found some time to relax and work on some electronics!  Here's the result: I built 3 ESP32-Prog prototype modules for the wESP32:

  They are built manually with the hot air rework station so they're a little messy, but they seem to work!  After adding a little patch wire that is.  It's nearly impossible to see, but on the top right corner of the CP2102N, I forgot the connection between pins 7 and 8.  So dumb: Eagle told me clearly there was an air wire left and I completely missed it.

  I tested them by connecting them to my PC and /dev/ttyUSB0 showed up.  Then I ran:
  

  screen /dev/ttyUSB0 115200

   and when I connected TX to RX, the characters I typed were echoed back.  What I haven't tested yet is whether the EN and IO0 management circuitry works.

  I have all the parts to build wESP32 protos as well, but I'm doing that one the "proper" way with solder paste, a stencil and reflow oven.  Hopefully later this week!
  

• Ethernet jacks

  Patrick Van Oosterwijck • 06/21/2018 at 20:05 • 10 comments

  Back from vacation and finally more or less caught up.  My Ethernet jacks arrived from Hanrun while I was away, 250 of them.  A quick check shows that luckily, they seem to fit my footprint:

  That's a relief! :)

  I've also been creating the BOM and crunching some numbers on pricing to get a better idea of what the BOM cost and COGS might be, and unfortunately it's higher than what I had been guessing.  Bottom line is that with the numbers I see, in low quantities this is likely going to be a ~$45 board to make it worth my while.  I know that's a lot more than most ESP32 boards, but usually the only "expensive" part on those is the ESP32 module.  Compared to other "normal" ESP32 boards, the Ethernet jack and phy add a good amount of cost, and the PoE power components like the PD chip and flyback add even more.

  So now the question is: would you still be interested in buying this board at that price?  Please comment!
  

• Proto PCBs arrived!

  Patrick Van Oosterwijck • 05/18/2018 at 15:33 • 4 comments

  First of all: terribly disappointed that my project didn't make it to the next round of the Hackaday Prize.  I tried really hard this time, checked all the check boxes they demanded... except I didn't make a hokey video in which I explain how great my stuff is I guess.  Congrats to the projects that went through, most very deservedly, others, less so... I don't think rotary encoders are a particularly hard problem to solve for instance, but let's leave it at that.

  This project will continue with or without the funding from Hackaday of course.  Maybe a little slower since my focus needs to be on things that let me eat instead, but it will happen.

  As for progress to report, I received PCBs and a stencil from Elecrow:

  They came out nice, the logo printed well in silkscreen and really "pops".  The white on black is looking good.  As I said before, I would likely target yellow on black for production boards, any opinions on that?

  Still waiting on the PoE Ethernet jacks from China, they will likely only arrive during my vacation, which is going to push any built-up prototypes well into the second part of June.  Let's hope they'll work right away! :)
  

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