Reset on ICSP header in Uno > Tiny programming

Other Hardware 3rd Party Boards
1

Hello, I recently put together a PCB which has a mating ICSP header for the port on the Uno, the target device is an ATTiny84. I found out after a couple of attempts that this doesn't directly work because pin 5 on the ICSP header connects to Uno Reset, and not SS, typically on pin 10.

It's not the end of the world as I can run wires, but it kinda defeats the purpose of my board.

The Arduino as ISP example seems to make out that it should be possible to use the header, the SS pin is defined in the code. I found a post from 2015 that suggests in the master > slave relationship, the master is defined by the device that resets the other, so is my misunderstanding down to the ICSP header being intended as an input to flash the Atmega828 and not an output for other devices? Is it possible to use this header in the way I want?

many thanks

2

No, you’ll need another wire to a pin to be used for reset to the attiny (which needs to be manipulated in ways other than “ss” would work, anyway. The isp connector on uno was primarily intended for isp TO the 328, and only noted for generic spi use after the mega came out.

3

Thanks for the reply, that is pretty much the conclusion I came to, not to worry - I have designed a shield which will have a socket for Tiny85, Tiny84 and a header to link to SMD or other types.

Thanks