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Topic: Adding extra AUX pins to BP 3.6 (Read 1713 times) previous topic - next topic

Adding extra AUX pins to BP 3.6

I have a Sparkfun, SEEED, and two Adafruit 3.6 bus pirates. I usually have multiple irons in the fire, and multiple BPs hooked up to them.

The other day I could have used a second AUX pin to toggle RST on a device under test. I know the BP4 has 2 extra AUX pins but I already have multiple version 3 BPs. I downloaded the 6.1 source and looked at the BP4 interface and how the extra AUX pins are controlled. The interface and code looks pretty straight forward.

Looking at the BP 3.6 the AUX pin is straight out of the processor, no external pullup. The AUX pin is a 3.3v pin 5v tolerant. The AUX pin comes off of RB10.

The ICSP header is pinned out and includes PGC and PGD. PGC and PGD are RB1 and RB0. They come straight off of the processor, just like the existing AUX pin, they are 3.3v but NOT 5v tolerant.

What do you think about using the PGC/PGD (RB1/RB0) pins as additional AUX pins on the BP 3.6?

As long as I stick with 3.3v interfacing, which more and more of my work is tending to, I should be safe.

Has anyone already done this? No sense reinventing the wheel.

I would keep the same cA/kA syntax as in BP4.

I see hints that the PB3.6 is code size limited. It doesn't look like a lot more code but am I going to run into problems trying to fit it in?

I am able to build the 6.1 source using the Microchip XC16 (v1.22) compiler and I get program space at 92% and data space at 66%.

Re: Adding extra AUX pins to BP 3.6

Reply #1
I would advise against using a pin that isnt 5v tolerant. It is ok if you are fully consent of it (you in your case ;)). however a slight moment of unattendancy would potentially fry your buspirate.