ESP32 autoreset

This little project utilises an ATtiny9 to automatically reset the ESP32 into bootloader mode

Gearloose

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Description

This little project utilises an ATtiny9 to reset an ESP32 into bootmode. It is used when programming the ESP32 with the Arduino IDE.

I thought it was a bit annoying that I had to manually put the ESP32 in to bootloader mode by pressing the buttons. So this hack utilises an ATtiny9 the micro sized 6 pin SOT23 device from Atmel.

It connects to the RXD line of the ESP (TXD from PC) and to the BOOT0 and RESET lines. When trying to upload the program from the Arduino IDE the ATtiny9 detects the bootloader signature that is sent from the PC to the ESP. It then automatically puts the ESP in bootloader mode. So the Arduino IDE can directly program the ESP32 without the user having to press any buttons. The ATtiny9 is super cheap and does not need any external components. I suppose this could also be used for the ESP8266. And it makes the use of the Arduino IDE with ESP32 much simpler. Also only the RxD and TxD lines are needed (with a CH340E for example).

Details

This code is for Atmel AVR ATtiny9
Connect ESP-EN to PortB0
Connect ESP-Boot0 to PortB1
Connect ESP-RxD0 to PortB2
Only a baudrate of 115200 is supported at this point
Do not program the ATtiny9 when the ESP32 is connected to the TPI lines
ATtiny9 needs 5 V to program but can run on 3.3 V
Outputmodes can be chosen between pushpull and opencollector at compiletime (see config.h)
RxD pin pullup can be chosen at compiletime (see config.h)
The baudrate is calibrated within a certain range
Arduino bootsequence to test with HTERM in HEX format: "C0 00 08 24 00 00 00 00 00 07 07 12 20 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 55 C0"

Files

espautoreset_attiny9_opencollector.hex

The HEX file. EN and BOOT0 need a pullup (pushpull version is also possible). Flash it with AVR Studio and ISP MK2 via TPI.

hex - 2.02 kB - 04/28/2019 at 15:22

Download

Components

1 × ATtiny9 ATMEL AVR ATtiny9 SOT23-6

Discussions

Jose Baars wrote 05/01/2019 at 12:46

The problem is the ESP32 dev boards. The enable pins usually have a capacitor that is too small
to keep the anble pin low long enough. With a 1 uF capacitor to the enable pin the standard nodemcu-cross-transistor circuit it works well. Making your own devboard fixes this and maybe other issues, like too few ground pins. Nice workaround though. More=better :-)

Are you sure? yes | no