Raspberry Pi Pico's built-in bootloader allows you to write firmware via USB or SWD. However, in some situations, other interfaces may be useful. Picoboot3 now offers the options of UART, I2C and SPI.
Your old Raspberry Pi and E-Ink display are about to become way more useful ...
Nucleo-144 (F429ZI, NUCLEO_F746NG, NUCLEO_F746ZG, NUCLEO_F756ZG) Discovery (DISCO_F746NG) STM32F4 boards (BLACK_F407VE, BLACK_F407VG, BLACK_F407ZE, BLACK_F407ZG, BLACK_F407VE_Mini, DIYMORE_F407VGT, ...
The ESP32 keeps finding new jobs in my house.