Olimex's Tsvetan Usunov has warned international makers to avoid trying to use Wi-Fi channels above 11 with ESP8266 and ESP32 devices, having run into reliability issues on a power cycle.
"Recently we are experimenting with Home Assistant installed on A20-OLinuXino-LIME2 Home server and attaching different nodes made with our ESP8266/ESP32 boards," Usunov explains, and noticed odd behavior of ESP[8266/32] when [the] Wi-Fi router is set on the higher frequencies channels."
A router in the workshop set to channel 13, automatically selected by the router as the channel least likely to experience interference, proved the problem: A device running ESPhome connected after three retries straight after it had been flashed, but if it lost power at any point would remain entirely disconnected — showing authentication errors as the problem.
"If we change the WiFi router settings to Channel 1-11," Usunov notes, "all problems now are gone and ESP connects every time no matter how many times power is cycled. Our blind guess is that ESP can’t connect reliable on the higher frequency channels. As far as you choose channels 1-11 everything is fine. We think that most people even do not notice this kind of errors if [their] routers are set to Auto channels as the chances to go up to 12-13-14 are very slim."
The problem could well lie in a lack of international testing: Only channels 1 through 11 inclusive are licensed for use in North America, with channels 12 and 13 available in most other countries. Channel 14, meanwhile, is exclusive to Japan — and limited to 802.11b operation only, for reasons of backwards compatibility.
Usunov's full analysis, including error logs from the device on test, is available on the Olimex blog.