Master-board not working without the flasher plugged in

[mnaveau]

Dear all,

I recently had a trouble with a master-board.
I am flashing the board. The board behaves correctly with the flasher plugged.
But when the flasher is unplugged the board does not boot properly.

Let me know if you have the same issue or a solution.

Best
mnaveau

[thomas.flayols]

Hello @mnaveau,

Can you confirm that you unplug the whole programmer and not the usb cable only? The reset line seems to be activated when the programmer is not powered…

[mnaveau]

I flashed the card in different ways after I notice something went wrong…
The last one I did to make sure was the following procedure:

• 1. plug the usb,
• 2. plug the programmer to the master board and the power from the usb as well
• 3. git checkout master on the master-board package
• 4. make flash
• 5. unplug everything
• 6. replug only the power from an another power source (not the usb one).
     => results is that the master did not boot: the status led is idle (dark) and a another green led is on (master board powered on).

[thomas.flayols]

Ok, to know if it is a power issue or a RESET line issue, after flashing the board, can you try to power the board from the programmer power, without the prog connector plugged? Does the board boot?

Another test is to power the board from your external power, and only plug the prog connector and to run make monitor.

[mnaveau]

After discussion with Thomas we notice that two components were missing.
In the picture below you can notice the absence of the resistance at R15 and C9

[thomas.flayols]

Thanks, your board is indeed missing the RESET line circuit (R15 C9)

esp32_master_board.pdf

You can solder this two components:
R15 is a 0402 4.7kOhm resistor
C9 is a 0402 100nF capacitor

the values are not very important (1 to 10k) (100 to 470nF) will probably work fine in case you have only different values.

Without this, the board is in the Reset state when reset pin is left unconnected, that explain why having the programmer plugged was working.

[fgrimminger]

o.k. - thank you!
We’ll add those two components.

[fgrimminger]

We have added the missing components - everything is working fine now.
Thank you!