Cannot set some pins to digital when #pin_select is used

dcm684 · Joined: 08 Sep 2010 Posts: 8

I am working on a PIC18F97J94 with CCS PCH 5.075. I am trying, and failing, to set several pins on the H port to digital when I use #pin_select. I have no issues setting the non-H-port pins to digital when #pin_select is used. I also have no problems changing the H-port pins to digital when #pin_select isn't used. The H-port pins all use ANCON3. I've tried using set_analog_pins() to do this as well as directly setting the ANCON3 register.

The only thing that I could do to get it working is using the pin_select() function. The problem with this is that there is more overhead, requires the fuse IOL1WAY to be off, and I cannot use the #use spi() and #use UART() helpers.

An example of the non-working code is:

newguy · Joined: 24 Jun 2004 Posts: 1909

I had similar issues with 5.073 and 5.074 last year with a PIC18F25K40. I had to implement the PPS assembly unlock procedure along with the proper fuse (forget the name) to allow it all. I then had to take direct control of the PPS registers to do what I needed it to do. I haven't tried that code with a newer release as it works and the thought of playing with it just to get it to work with the CCS functions honestly turns my stomach.

Try "doing it the hard way" and see if you can gain full control of port H.

dcm684 · Joined: 08 Sep 2010 Posts: 8

Thanks newguy.

I went deeper into it and found that if I clear the bit, IOLOCK, I can change the values in ANCON3. I then re-set IOLOCK. This requires the fuse NOIOL1WAY.

Another interesting tidbit is that I can set the bits of ANCON3 even if IOLOCK is set. I just cannot clear the bits unless IOLOCK is clear.

Ttelmah · Joined: 11 Mar 2010 Posts: 19549

That is really odd!...

IOLOCK is not meant to affect ANCON, just the PPS control. Wow.
I would suggest reporting this to CCS and possibly MicroChip.
Presumably, since you were seeing the problem only with PortH, it is not happening with the other ANCON registers?.
It does sound as if you have found a chip 'oddity'.
Certainly one designed to drive you mad.

Just a teeny bit 'puzzled' though by your comment about not being able to use the #USE SPI 'helper' and #PIN_SELECT. Of course you can use #PIN select and #USE RS232 and #USE SPI. Just select the pins, and then use the port name in these. Look at the sticky at the head of the forum for how to do this.