I have a relayboard, ESP-01/0S1 with a ESP8266 on it. The GPIO0 pin from the ESP8266 drives the relay.
On the boot it raises GPIO0's level high, 5V. Not optimal but I could cope with it.
This, with the "factory" firmware as reported by:
AT version:18.104.22.168(Jul 1 2016 20:04:45)
However, when I install a firmware/scetch using Arduinon's IDE, even a trivial one which doesn't touch GPIO,
after a power-cycle/reset GPIO0 does a quick toggle: up and down. This is a real problem because it triggers the relay
and makes it useless for driving something like a garage door controller.
As the behaviour changes with the firmware change I think/hope it would be possible to make/modify a firmware
to make it let alone GPIOs and let the user configure it, like Linux does it. For those not familliar with Linux:
before declaring GPIO's pin direction (In/Out) you can specify its level, on boot the pin is floating. Smart.
Currently I have a Raspi Zero with a relay which does the job, wanted a cooler solution but failed
Any help would be greatly appreciated.