Programming TinyPico Nano (ESP32) from UART

[raff5184]

Hi,

I have a tinyPico Nano
https://www.tinypico.com/tinypico-nano

that I program from Arduino IDE using USB connection. What I am not able to do is programming the ESP32 directly from UART bypassing the USB-to-UART bridge of the board. I tired 2 different USB-to-UART bridges and connected them directly to pin IO1-TX and IO3-RX  of the tinyPico but the issue is that Arduino IDE doesn't find the TinyPico board when I use a different bridge


Some more details:
the tinyPico Nano board has a USB/UART bridge chip (cp2104) so that it is connected to a PC USB for programming the ESP32 of the board. But when the ESP32gets programmed, serial/uart communication is actually used.

What I want to do is bypassing the cp2104 and use an external chip to do the same thing and connecting this external chip to the UART pins of the tinyPico. I tried with 2 different external chips but no luck, because when Arduino IDE tries to program the tinypico, it can't find the board

[PlainName]

The ESP needs DTR and RTS toggled in a specific way to enter boot mode (that's EN and IO0 pins on the ESP). Perhaps you haven't connected those? They don't connect directly, either, but kind of block each other. A quick way to find out if this is the problem is to manually toggle them in a random order - eventually you'll hit a sequence that works

[raff5184]

yes, that was my last understanding and I played around with them a little.

When it is programmed automatically from USB, EN is HIGH all the time and IO0 is HIGH pulls LOW for a moment and then HIGH again before programming starts. And same thing at the end of programming.
I did the same but no result yet. I should probably try a different combination (?)

[PlainName]

You can find the details here:

https://github.com/espressif/esptool/wiki/ESP32-Boot-Mode-Selection