PIC18F2431 and SPI

temtronic · Posted: Wed Feb 08, 2012 1:48 pm

I suggest looking in the examples folder and open up a few of the examples that have SPI code inside them to see how CCS handles it.

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

This example uses software SPI for the master and
hardware SPI for the slave (all in the same PIC):
http://www.ccsinfo.com/forum/viewtopic.php?t=26888

Here is an example of hardware SPI for master and slave (using 2 PICs
on separate boards):
http://www.ccsinfo.com/forum/viewtopic.php?t=39145

If you need more help, use the forum's search page to search for

brutus · Joined: 14 Apr 2004 Posts: 12

Thanks both for the suggestions;
the fact is not "how" to use SPI, I've read a lot of documentation ( from microchip and CCS ) and I'm quite sure that the code is working...also because it's so simple and i'ts been used form another guy

http://www.ccsinfo.com/forum/viewtopic.php?t=43461

The problem is: could be the micro? Do I need a particular configuration?

I really don't know...something from the pins should go out!

C

temtronic · Posted: Thu Feb 09, 2012 6:26 am

hmmm...

I don't have that PIC / compiler so....

You could cut code for a simple LED blinking program and see if the PIC is alive and well,toggling all pins.esp. the SPI ones.

You might try removing the set_tris() and fast_IO functions...

Also check to see what other onboard peripherals might be enabled in the default configuration.

All of these tests would narrow down the problem.

brutus · Joined: 14 Apr 2004 Posts: 12

Hi temtronic,
I've just done a lot of tests; the led is blinking, other functions seem ok, and I've tested many different configurations...

I'm sure that the problem is somewhere else, but in this moment I can't find it.

Thanks again for the suggestions..
Claudio

Ttelmah · Joined: 11 Mar 2010 Posts: 19513

Question - what compiler version?.
Have used the SPI on the 2431, without problems. Yours, may be a 'version specific' problem with the compiler.

Best Wishes

brutus · Joined: 14 Apr 2004 Posts: 12

Hi,
my compiler is 4.110.

Just to check, could you post the code you've used for the SPI?

Thanks,
Claudio

Ttelmah · Joined: 11 Mar 2010 Posts: 19513

Unfortunately, the SPI is fairly 'scattered' through a largish project, so not easy to pick out. 'm actually running as switchable master/slave. Things different that I notice:
1) Running much faster. clock/4, not 64.
2) I try to avoid using fast_io mode on pins for the hardware peripherals. Makes future portability much easier to other chips. So using standard_io mode on the SPI pins.
3) Have a bodge in place, where I switch to slave operation, for the erratum regarding this - you have to verify the incoming clock line is being held to the IDLE state for the mode you select, before switching to slave mode. Obviously should not apply to a master only device.

Using SPI Mode2.

However none of these would seem to affect your behaviour, so the next thing is to compiler your code with 4.110, and look at the assembly to see if it does correctly configure everything - it looks as if it should.....

Best Wishes

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

brutus · Joined: 14 Apr 2004 Posts: 12

Hi,
1) according to the PIC18F2431 DS, the hw pins for SPI are

RC4 - SDI
RC5 - SCK
RC6 - SS
RC7 - SDO

So I expect to see some signals over C5 and C7 in MASTER configuration. Is it correct?

2) I've a last generation digital oscilloscope, and I'm quite sure to trigger the signal.

3) I'll try with a short delay.

Thanks,
C