ESP32 Forum

My WROVER custom board has an RS-232 serial port rather than USB. I implemented the automatic programming circuit as in https://dl.espressif.com/dl/schematics/ ... _SCH-2.pdf with 2 NPNs, a 12K pullup on EN over 2nF, and a 5 K pullup on GPIO0 over 1nF. In my case GPIO2 is open

What's odd is that the circuit works fine to get the board into flash mode. And you can ID the board and get the MAC. But then the flash id phase fails, and so does the flash write. Those pins are not used in that phase at all.

Log: I've debugged into esptool.py, stepped through, and both IOs seem to be doing exactly what they should. And by stepping through, I've slowed it down so the cap values and delays in the code should not be relevant.

I realize now that V2 may not have been the best model, since these circuits have changed. But I can't see why what I'm measuring does not work.

There is apparently some black magic with this pins. Why isn't what's depicted here working?

Is it just not reliable like: https://esp32.com/viewtopic.php?f=12&t=12154

Thanks!

FWIW, I found the issue. RTS and DTR should have been inverted. Using FT_Prog on an FTDI adapter, you can just program the part to invert those outputs to active when low. The difficulty was is in diagnosing when those 2 inputs trip each other through the NPN pair.

Here's what a correct sequence looks like for anyone who might be having the same problem.