Flashing the AVR through Wifi
From Just in Time
Wifi flashing through ESP8266
After a long search and many discarded ideas, this hackaday page points to esp-link, an esp8266 firmware dedicated to providing a transparent wifi-serial bridge.
This page lists available esp8266 modules. I've got an esp-01 (and several esp-03s).
The tool esptool is documented here. This page also explains how to connect the gpio pins to get the device into serial programming mode. Notably:
- GPIO0 to GND to select serial bootloader.
- GPIO2 to Vcc using a resistor
- GPIO15 is already pulled low on the module (apparently)
Flashing the esp firmware
my command line (given the 4Mbit flash, see instructions here:
esptool.py --port /dev/ttyUSB1 --baud 115200 write_flash -fs 4m -ff 40m 0x00000 boot_v1.6.bin 0x1000 user1.bin 0x7C000 esp_init_data_default.bin 0x7E000 blank.bin
- bluetooth (HC05) appears too unreliable