I/O on the ICSP connector

Projects Programming
1

I'm building a breadboard system with an ATMEGA328P. To keep things really simple, I had the idea of installing an ICSP connector and using a USBASP to program it. It occurred to me that I could use the same connector to drive a MAX7219 based LED display. Hey, they're already there, with power and ground available too, right?

I have all the hardware sitting in front of me. However, I realized that my program would set those pins to output mode. So I wonder if that would damage the USBASP programming device, once the program is loaded? It would still be attached, at the time that the program is loaded into the AVR.

Is there a risk? Or does the USBASP hold the device in reset until it is detached (for example)?

Thanks.

2

I'm not totally sure with USBASP. But with my PICkit2 (yeay yeay, it's not Atmel but I think USBASP is smart enough as well...) the programmer only drives his outputs when the devices entered programming mode, so after a reset. Once it is programmed the outputs are set to high Z and the reset is released. So it does nog damage anything.

And I think it's the same with a USBASP. Even though you never used the ISP header itself to connect to anything, the ISP pins are just shared with the shield breakout pins...