Multi-AVR Upload Board

Hello All!

I've drawn up a schematic for a board that sits multiple AVR chips and incorporates an FT232RL layout pulled from an FTDI Board. The intention is to have one board that will sit various microcontrollers into IC sockets of which can be uploaded to more efficiently. (schematic included below)

I have a couple of questions:

  1. Can 2 microcontrollers share the same external crystal providing only one is powered via the 4-way 5V switch?
  2. Can all microcontrollers share the TX and RX lines providing only one is powered at any time? In other words, should the IDE be able to recognise and upload to the chosen board if there is another un-powered controller on the circuit?

Note: I understand the placement of TX and RX on the ATTINY's may be incorrect/need an alternative method, however this is more of a hypothetical sketch. I believe the 1284p & 328p to be correct.

Thankyou greatly for any responses!

  1. Not sure, but it should work with independent oscillator even both MCUs will be powered.
  2. Yes, the Rx and Tx are disconnected if the MCU is not powered even if the MCU is powered and the RESET is LOW. However, the IDE can recognize nothing. Part type is mandatory for avrdude which is used for uploading.

Brilliant information! Thankyou

You are making a board with multiple sockets, one for each 4 types of AVR MCU ?
So the use case would be that when you want to load a sketch onto am MCU, you would plug it into the appropriate socket and program it, possibly extracting it from its current board to do so ?

I could see the value of such a device for the one off operation of loading the bootloader, if you do this often enough. However, that would require another type of programmer (ICSP). I don't see the benefit for loading sketches.

What happens if you want to view the serial console of one of the chips you have so programmed. You would anyway have to do it with the chip back in its current environment with all its attached modules etc. so you are more or less back to a direct connection between the FTDI device and chip under test.