Faulty ESP32-S2 Saola Boards

[matt001k]

Hello all,

Recently I have done a project for client over in Europe and completed the prototype not too long ago. I won't disclose full details on the device but basically, in order to connect the device to the internet, an http server is instantiated in soft-AP mode in order to take user credentials. When first booting up the device(if not already connected to the users wi-fi) a scan is done of the nearest APs and it is written to a JSON file in SPIFFs and served through the device on a drop down menu in a web page.
When doing this from my own personal living space I can pick up anywhere from 30-50 APs (due to heavily congested area) and have seen no problems with connecting to the ESP or the internet.

When my client tries the same developed firmware over in Europe(I am from USA), when wifi is scanned he only maybe half of the time receives APs surrounding him even when close to access points. He noticed when placing the device in a coffee mug, that he is able to pick up the access points every time, so this had me believing there was cross-talk between signals, he moved the device away from any type of RF devices and had gotten routers very close by but not others in a near vicinity after doing a scan. He also analyzed the wifi of nearby APs when the device is in soft AP mode and noticed that, even when near the device he gets weak signal strength(-80dBm at about 5-7 meters away from the ESP). This made me believe that the dev boards he has ordered is faulty after testing all 3 dev boards he bought from Digikey.

So my question is, is it possible all 3 development boards are faulty (all saola development boards from Espressif directly) or is there something else that may be going on?

This scares me as the project develops further, I am not sure if I will want to use a WROOM module for a prototype board due to the issues were having.

Hope to hear from you all soon!
Thanks.

[ESP_Angus]

Hi Matt,

Could your client please double check exactly which model of Saola they have? Digikey sells Saola boards with both the ESP32-S2-WROOM (PCB antenna) and the ESP32-S2-WROOM-I (Ipex antenna socket).

If they have the WROOM-I module and no antenna plugged in then the behaviour may be quite unexpected (I've fallen into this trap myself at times - the module can still connect to some networks but performance is understandably terrible and easily swamped by other signals.)

If this isn't the case, then can you please confirm that no other hardware is connected to the Saola board itself? Can your client try powering the board in a different way (for example, connecting to a different computer?)


Angus

[matt001k]

Angus,

Thank you for the reply, I noticed that the board that he has is the WROOM-I dev kit. The rate of scanning and properly finding the correct networks is about 40%. I've had him connect far away from any RF signals and he even turned off any IOT devices/RF devices within his home and it was still the same.


Do you know why the WROOM-I has such poor performance? It still includes the antenna PCB trace does it not?
Get back to me when you can.
Regards,

Matt

[ESP_jakob]

Hi Matt,

What Angus is basically suggesting is to connect an antenna to the board via the IPEX connector. Please let your customer connect an antenna and try again. Without the antenna, it won't work anywhere close to properly.

Best,
Jakob

[ESP_Angus]

Hi Matt,

Do you know why the WROOM-I has such poor performance? It still includes the antenna PCB trace does it not?

There is the same PCB antenna as part of the WROOM-I PCB but if you look closely at the antenna feed line then there is a small 0 ohm resistor which can only connect either the IPEX antenna port or the PCB antenna. This is R6 & R7 in the datasheet schematic, and only one is populated at a time.

It is possible to switch the WROOM-I to use the PCB antenna, but only by desoldering and moving this part. Without either doing this or connecting an IPEX antenna to the socket, the performance of a WROOM-I module will be very poor.

[matt001k]

All,

Thank you for the responses. It looks like we will be getting the correct board around this time.
He did stick a jumper wire in the antenna socket and strangely enough it began to pick up APs!
Again thank you for all the help!

Regards,
Matt

[ESP_Angus]

Hi Matt,

Good to hear. Just one note, according to the datasheet the antenna port shouldn't be operated open-circuit or with an incorrect impedance antenna attached. There is potential that running the ESP32-S2 with no antenna (or a random jumper wire antenna) will damage the RF circuitry.

Anecdotally, they seem pretty tough - as I mentioned I had a development board on my desk for quite a while before I realised the poor Wi-Fi performance was due to a totally missing antenna, and it seems to have held up fine. But something to keep in mind if those boards show reduced performance in the future (with the antenna!)