B4R Question Slow clocking ESP8266

[peacemaker]

Hi, All

I'm assembling and flashing ESP8266 units basing on NodeMCU boards.
All the time 7...10 pcs were fully the same work on the same .bin FW.
The sketch is based on self-reset each minute, and the minute counter is saved into RTC-memory OK. The minutes period is variable, is set by command from a server.
And periodical subs are called basing on this minute counter.
All controllers are re-flashed by OTA from the same .bin file.

But suddenly i have met 2 controllers after those 7...10 pcs where the minute counter is changed each ... 3 minutes exactly, instead of 1 min. So -periodical subs are called 3 times more rare. It's sending via WiFi to a server sub.

Maybe anyone knows such situation ? Why so?

 

[peacemaker]

Strange investigation:
1) if ESP8266 is far from WiFi-router - all works OK !
2) But if to place it very near to the WiFi router (10....50 cm) - such strange work - 3 times more rare sending to a server.

 

[agraham]

But if to place it very near to the WiFi router

Asking for trouble! Probably parasitic voltages being induced in wiring/PCB traces by the relatively high field strength close to the router, the effect probably enhanced because the low power CMOS circuitry is relatively high impedance.

 

[peacemaker]

But why it's sharply 3 times rarely ? Exactly 3.0 minutes instead of 1.0 minute.

 

[agraham]

Who knows? I don't. But it's obviously a radio-interference problem as moving it away from the router makes it behave as expected. If you intend a serious use for it I would put in a metal box so it is within a Faraday cage as it does seem susceptible to interference.