GPIO16 as output on ESP12S

ESPHome
1

Hi, ESP newby here.
I bought a ESP12S based development board (link). Unfortunately I cannot find much information about the board, but I did find the datasheet of the ESP-12S module itself. It is supposed to have 9 IO pins, which (by luck) matches my needs. I would like to attach 4 push-buttons and 3 relays right now and add one (or more) I2C sensor(s) later. However that also means I need to use GPIO16 as an relay output, but I’m having trouble getting it to work. I managed to get the four push-buttons and 2 relays to function properly. The last relay which I would to control via GPIO16 is giving troubles. If I understood correctly, GPIO16 differs from the other GPIOs since it has an internal pull-down instead of an internal pull-up and that it is used to wake from deep sleep. I’m not planning to use any deep-sleep, so that should not be an issue. I conducted a small series of experiments, but the results do not make sense to me: (first line of the table is for reference only):

pull Inverted Code Behav without relay Behav with relay
none No - platform: gpio
pin:
number: GPIO15
name: Two		 Boots normal
off: 0.3mV
on: 3.24V		 Short relay on/off flash during boot
off: 0.4mV - 0.0mA
on: 3.19V - 2.0mA
none No - platform: gpio
pin:
number: GPIO16
inverted: False
name: Three		 Relay on during boot - then reboot loop
0.3mV - unstable		 Relay on during boot - then reboot loop
0.3mV - unstable
none Yes - platform: gpio
pin:
number: GPIO16
inverted: True
name: Three		 Boots normal
off: 0.3mV - unstable
on: 0.3mV - Goes into reboot loop		 Relay on during boot
off: 0.3mV - unstable
on: 0.3mv - Goes onto reboot loop
INPUT_PULLDOWN16 No - platform: gpio
pin:
number: GPIO16
mode: INPUT_PULLDOWN_16
inverted: FALSE
name: Three		 Boots normal
off: 0.3mV - unstable
on: 0.3mV - unstable		 Relay on during boot - then reboot loop
0.3mV - unstable
INPUT_PULLDOWN16 Yes - platform: gpio
pin:
number: GPIO16
mode: INPUT_PULLDOWN_16
inverted: True
name: Three		 Boots normal
off: 0.3mV - unstable
on: 0.3mV - unstable		 Relay on during boot - then reboot loop
0.3mV - unstable
INPUT_PULLUP No - platform: gpio
pin:
number: GPIO16
mode: INPUT_PULLUP
inverted: False
name: Three		 Boots normal
off: 0.3mV - unstable
on: 0.3mV - unstable		 Relay on during boot - then reboot loop
0.3mV - unstable
INPUT_PULLUP Yes - platform: gpio
pin:
number: GPIO16
mode: INPUT_PULLUP
inverted: True
name: Three		 Boots normal
off: 0.3mV - unstable
on: 0.3mV - unstable		 Relay on during boot - then reboot loop
0.3mV - unstable

Anybody any idea what is going on here and how to get GPIO16 working as a switch? Should I use a hardware pull-up or pull-down? What should be the value?
I could also connect a scope, but since I do not own one myself it’s a bit harder to do so.
I could also just get another board with more GPIO pins, but I still what like to understand what is going on here.

2

I only just now realized that an input pull-up and input pull-down doesn’t make much sense on an output. Still stuck on the fact that board goes into some kind of reboot loop when GPIO16 goes high low.

3

Have you seen this page? ESP8266 Pinout Reference: Which GPIO pins should you use? | Random Nerd Tutorials

4

Yes, I have, and many other pages with similar info. My conclusion from most of them is that it can work like I want it to work and also that I’m actually doing it correctly. Still, it doesn’t work, therefore I’m seeking help. For now, I think that the issue it is related to the specific development board I bought. Is seems that GPIO16 and the reset pin are connected (through a 470 Ohm resistor) on this board. That would make sense if you want to use the deep sleep functionality. I asked the seller for the schematics and support. If that is not successful I’ll buy an ‘official’ Lolin D1 mini and try again.