Wifi / Bluetooth Problems with custom Board

[pathob]

Hi,

we have developed a custom board based on the ESP32 (ESP32D0WDQ5, revision 0) and are facing major problems with Wifi and Bluetooth. We are not able to connect to a station or to create an access point at all. The only thing that is working is scanning for networks. For example, this project (https://github.com/VALERE91/ESP32_WifiScan) is working on our boards and shows better RSSI values than other working development boards like Nano32. Bluetooth does not seem to work at all.

We are using a ceramic antenna that we have already used on many other custom boards. We are quite sure that antenna impedance matching has been done right. We are using 40 MHz crystals that are running slightly slower (39.996 MHz). We measured the noise on the supply voltage and it is comparable to the noise of the Nano32. We are using external memory with 1.8 V and 32 Mbit (MX25U3235FM2I-10G), the external RAM (LY68S3200SLT) is currently disabled. The external RTC crystal was not working and is currently disabled.

Is there anything that we might have forgotten? Have you any ideas what we can test why Wifi / Bluetooth is not working?

Thank you in adavance for your responses!

Edit:

I added verbose logs for working and failing boards. The code can be found here https://github.com/pathob/esp32-connect-example

[pathob]

No suggestions?

[BrucePerens]

I'd suggest you start by taking a look with a spectrum analyzer connected to a nearby antenna, just to make sure you have WiFi on the right frequency and at a reasonable amplitude.

[Lucas.Hutchinson]

Check that you have a full ground plane underneath the crystal.
We has a similar problem with the debug uart lines going under the crystal.

Also try contacting espressif directly via email. Their hardware support team is great and really helpful.

[ESP_Angus]

Hi pathob,

Sorry for the slow reply.

We are using 40 MHz crystals that are running slightly slower (39.996 MHz).

This is most likely the problem. The relevant document is the ESP32 Hardware Design Guidelines (available from the documents page), section 2.1.4 "Crystal Oscillator" which specifies +/-10ppm. It looks like your crystal is out by 4kHz, ie 100ppm, before considering any relevant tolerances.

I would guess that you can scan but not associate because the ESP32 is being a little more liberal in what it accepts as a valid WiFi frame than the router which it is trying to associate with.

[pathob]

Thanks for your replies!

Yes, we already checked the frequency on a spectrum analyzer and it looked good.

And yes, we have a full ground plane under the crystal.

And today, I removed the 40 MHz crystal and soldered a 26 MHz crystal taken from an ESP-01 on the board. Now, even scanning did not work at all. Of course, I changed the main crystal frequency in menuconfig. This is really weird...

Any further suggestions what we should check? Is it possible that we received faulty chips?

[JimmyPedersen]

Just guessing but can it be a power supply issue?
Takes a lot more power to connect to an AP than to just scan for them.
Are you sure you can supply enough power to the ESP? Do you have sufficient decoupling next to the power pins?
Good luck
Jimmy