ESP8266 Community Forum

hi
I have a circuit that I designed myself But I encountered a problem
esp8266 works fine, but when I replace uln2003 in my system and restart my system, esp8266 does not work anymore and i have to separate it and replace it again.

You have to be more specific, I'm afraid.
The ULN is a darlington array, mostly used to drive stepper motors (if I recall correctly).

Something like a schematic would be nice to show and the type of ULN2003 you're using (TTL, CMOS, PMOS).

What GPIO pins are you connecting to the ULN2803?

If GPIO-0 or GPIO-2 then the problem might be the loading on that pin preventing the ESP8266 from starting the loaded program. The ULN2003 has a 2K7 Ohm resistor on the inputs before the base of the transistor. That may be too low for the ESP8266 on those two pins.

If this is the problem then you may be able to use a stronger pull up resistor (lower value) to bring the voltage on the pin higher at startup.

You opened the same discussion in another forum, received several guidelines with possible explanations for the root of your problem, and still left the subject open 4 days ago with no updates, and now you're doing it here too? If that's the case, why did not you put all the required information ?

rudy wrote:If GPIO-0 or GPIO-2 then the problem might be the loading on that pin preventing the ESP8266 from starting the loaded program.

Yes, he's using GPIO2 pin: