B4R Question WeMos WiFi not working [SOLVED]

[Computersmith64]

Hi all - I have stumbled across an issue with a WeMos D1 R2 board that has me a bit stumped.

I have a flow sensor connected to the board - the power & ground are coming direct from the 12v power supply I'm using & the output from the sensor is connected to D4 (so I can see the LED on the board come on when the sensor output is high).

The issue I am seeing is that whenever the board is powered up, if the sensor output is high, the WiFi on the board won't start up. Also, when it's in this state even if I disconnect the output from the sensor (by pulling the pin out of D4), the LED on the board stays on - so I suspect the board has gone into some weird frozen state. If I power the board up with the output from the sensor either low or disconnected, everything works fine.

Has anyone else experienced this issue? If so, is there a way to work around it? I've tried not initializing the D4 until after I've started the WiFi in AP mode, however I think this is a hardware issue so that's not helping.

Thanks,

Colin.

 

[Computersmith64]

OK - so it turns out that setting certain pins high/low puts the board into various boot modes:

a) GPIO15 (D8) - high state makes go go to sdio mode (sd card boot mode)
b) GPIO15 (D8) - low, GPIO0 (D3) - low, GPIO2(D4) - high = UART download mode
c) GPIO15 (D8) - low, GPIO0 (D3)- high, GPIO2(D4) - high = boot from SPI

The occasions that D4 was high on boot would have put the board into UART download mode. Problem solved by moving the sensor output to one of the digital inputs that won't affect boot mode if it's high on startup.