Getting an AT / ATtiny microcontroller ready for serial port Arduino programming
To be able to program using just the serial port pins you need your AT/ATtiny to first be programmed with a bootloader, as has been done on the microcontroller fitted on an Arduino manufactured PCB.
There are many, we’ve used successfully
You use “burn bootloader” from the Arduino IDE
Serial Port Programming
Once the bootloader has been programmed the AT/ATtiny can then be programmed using the UART TX and RX pins, BUT you also have to use the RESET pin as the arduino must be reset for programming to be carried out. For this reason its often simpler to use an Arduino UNO (for 5V parts) with its microcontroller removed over say a FTDI USB serial cable. See here
To program the bootloader running AT/ATtiny in circuit you have to connect:
- The 2 UART serial port connections: TX, RX
- The reset pin
Gotchas to watch out for!!!!
AT micro’s can have duplicate pins for the same port! For instance the ATtiny841 has TXD0 and RXD0 duplicated and the bootloader will only work for one pair! A good idea can be to find a development PCB and see which pin they have connected to