Hy everyone
I just searched for simillar issue i have but couldn't find it so help would be appreciated
Problem is that when board is powered off and then powered on while analog input has some above threshold voltage (like 2V and above), it wont boot up and start working until i remove that voltage and then it boots and starts to work
Then i connect same analog voltage to the same input and everything it works correctly
Also i noticed that uploading code won't work if same analog voltage is present and then i turn pot whole left and then it uploads
When it fails to upload compiler warns that i should disconnect gpio's before another try so obviously there is some kind of protection regarding this
I made few different programs and they all have same issue
For example, yesterday i lost power to my house and fridge with arduino thermostat didn't start when power came back because pot with which i set desired temperature is above mentioned threshold voltage
Then i turned pot to the ground, arduino (TTGO LCD, ESP32) immediately booted and i returned the pot right where it was before shutdown and everything continued to work ok
In general i don't mind this but when fridge won't work after shutdown it's a problem
Any thoughts?
Thanks
You must not have power onto an input if the Arduino is not powered as it can damage it . 2v is likely to be above threshold where the input protection diodes conduct , putting voltage onto other components preventing your boot up.
By doing this you are back Powering it “ fugative power “ via the port and its condition is then uncertain .
Thanks for reply
But how then should i connect that analog input so that's maintenance free?
Another output with time on timer which holds it before another power up?
Yeah i had some thoughts in that directions also, that makes sense
So for this particular program for thermostat i used A14 and A15 inputs for sensing fridge temp and temp setting
Also i forgot to say that i have one other board with two analog input on other TTGO board but i used A0 and A17 inputs and no such problems on it so probably its like you said
Can you please elaborate more which analog inputs are critical and why?
Tnx
Just match up the GPIO numbers with the TTGO GPIO numbers to see which ones you should not use.
Any GPIO that mentions the word boot or strapping pin in the notes column should be avoided.
I see that the TTGO ADC15 is GPIO12 and that pin is used during boot.