Sonoff Relay, UDP SendTo, and Wifi interference

[mrh_icb]

I ran into an interesting issue, when trying to use Global Sync / ESPEasy P2P to network several Sonoff BASIC relays.
It seems that RF interference is caused by the Sonoff relay, which causes UDP packets dopped over Wifi. I thought I report my finding, in case anybody runs into it.

I used 2 Sonoff BASIC R2 relays, with an external switch on GPIO-14 each. Operating the switch on either unit shall flip the relay on both.
I enabled Global Sync / P2P on both, and assigned unit number 1 and 2.

First the non-working code, the sendto command never worked. It seems the UDP send gets disturbed by the local relay operating on GPIO-12.

Code: Select all

on switch#state do
  if [relay#state]=1
    gpio,12,0 // turn off local relay
    sendto,1,gpio,12,0 // turn off remote relay
  else
    gpio,12,1 // turn on local relay
    sendto,1,gpio,12,1 // turn on remote relay
  endif
endon

After lots debugging, the solution was to simply switch the order of commands:

Code: Select all

on switch#state do
  if [relay#state]=1
    sendto,1,gpio,12,0
    gpio,12,0
  else
    sendto,1,gpio,12,1
    gpio,12,1
  endif
endon

[Ath]

Does this also happen when switching another gpio? For example gpio 2, instead of 12.

[TD-er]

To me it looks like the extra power drawn from the relay may make the WiFi a bit unstable.

Can you at least also try with enabling sending Gratuitous ARP to see if it changes behavior?