ATtiny9-Based Module Can Reset an ESP32 Into Bootloader Mode

Electronics purveyor Gearloose has designed an interesting little module that utilizes an ATtiny9 8-bit AVR microcontroller to automatically put an ESP32 into bootloader mode, which is done when programming the ESP32 with the Arduino IDE. Gearloose states, “I thought it was a bit annoying that I had to manually put the ESP32 into bootloader mode by pressing the buttons. So this hack utilizes an ATtiny9 the micro-sized 6-pin SOT23 device from Atmel.”

The device functions by connecting to the RXD line (TXD via PC) of the ESP32, as well as the BOOT0 and Reset lines. When you upload a program from the Arduino IDE, the module detects the bootloader signature and puts the MCU into bootloader mode automatically. This allows you to program the ESP32 without having to press any buttons, as the ATtiny9 emulates the process for you.

“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),” Gearloose explains.

For those looking to recreate the build, Gearloose has uploaded all of the schematics and code necessary to do so. This seems like overkill, in my opinion, especially if you rarely reprogram an ESP32 module for other tasks. That said, it’s a perfect device if you need to reprogram several or more MCUs for different workflows.