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Topic: ISP pins, dedicated? (Read 716 times) previous topic - next topic


Oct 24, 2010, 07:19 pm Last Edit: Oct 24, 2010, 07:20 pm by Intosia Reason: 1

Im was wondering if the ISP pins (miso, mosi etc), need to dedicated for ISP programming? Or can the pins be shared with peripherals? For ex. be connected to some LED's or select pins of a multiplexer. Because i really need all the pins i can get... And im using a 644 already :P

Mark S

You can use them all you want. They are need for example for I2C and other things. They only get used as ISP pins when you connect an ISP programmer to them. The ISP programmer puts the processor in RESET and then does it thing.


Coding Badly

You can use them all you want

Are you certain?

I have to remove a piezoelectric buzzer from MOSI or programming consistenly fails.  I imagine there are other devices that should not be connected / powered while programming.


They only get used as ISP pins when you connect an ISP programmer to them.

Wrong.  They're connected to MISO, MOSI, SCK, (also known as digital pins 11, 12, 13 on the Arduino) RESET, 5V, and GND.

It is possible to use them as long as you either a) never use ICSP, b) are very careful about what is connected so that it's compatible with dual use, or c) unplug everything on those lines before you use ICSP.



They are multi-use pins (except for RESET.)  If you want to use them for BOTH ISP and some other use, you'll have to be somewhat careful about the "other use."

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