mod-wifi-esp8266-dev Rev A only boots after soft reset when uploading firmware

Started by Darkness, April 19, 2021, 11:12:33 pm

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Darkness

Hi,

Quite some time ago, I got a mod-wifi-esp8266-dev REV A and recently I decided to experiment a little with it.

A simple noob tutorial to get started would be helpful, but after some time I realized that bringing pin 21 to ground when powering the device activates bootloader mode without having to mess with the solder pads.

I did some simple tests with arduino IDE (blink led, connect to wifi, temperature sensor).
I am using a SH-U09C, FT232 based USB to Uart to upload new firmware but also to power the device (for now).

Programming the sketch with arduino IDE is working which is followed by a soft reset to start the firmware.
This seems to work as expected and starts blinking the led, send serial data, connect to wfi etc...

However, if I just power on the device with serial port connected, nothing happens. No blinking led, no data on the serial port.
The solder pads are in flash mode (I did not change that).
I have just the Vcc, GND, Tx and Rx pins connected and a temperature sensor on pin 16 - GPIO 12.


Is there perhaps something that I missed?
Should I bring a certain pin to ground or Vcc with a resistor to get it booting the program when powering the device?

I tried bringing pin 21 - GPIO0 to Vcc with a 4.7k resistor, but that does not seem to help.