18F452 SPI DEBUG problem

aaron · Joined: 07 Sep 2003 Posts: 6

Hi folks,

Something realy strange happens when I run the PIC code without the debugging cable. The PIC talks SPI as a slave with another processor (master) and everything goes fine if the debug cable is plugged in. If I recompile the code without the DEBUG and program it into the PIC it looks like the PIC is able to just receive data but it stops sending. Not a single line of code is changed. If I scope the data out line all I see is a big flat line. Nothing.
Any ideas ? Has anyone seen anything like this ?

On the PIC errata they talk about some issues with the MSSP hardware but I don't think is the case.

Any clues about what is going on ? Same code works with the debugger and doesn't when the code is programmed into the target.

Thanks.

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Here is my setup:
CCS PCH C Compiler, Version 3.186, 18728
Debugger : MPLAB ICD2

Config code:

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

The first question is, have you been able to make any program
work in stand-alone mode ? Or is it just this one program that doesn't
work ?

aaron · Joined: 07 Sep 2003 Posts: 6

Yes. My program runs ok. The ONLY issues is the SPI traffic from PIC to the other processor. Nothing goes out. Everything else seems to work fine.

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

I don't have PCH 3.186, so I used vs. 3.188. Also, my test board
has a 18F458 on it, instead of a 18F452, but they are similar chips.

I made the following simple test program, and it works.
The PIC puts out groups of pulses on the SCK and SDO pins.
I suggest you try this program. Change the preprocessor
statements as required, to match your hardware.

It should work. If your own program doesn't work, then
post a test program, similar to the one I've done below,
but with the methods that you're using. ie., #fast_io,
PLL x 4 oscillator mode, etc. What I will be looking for
is things like the proper set_tris_c() statement, proper
declarations of register addresses by use of the #byte
statement, etc. So make sure you post a full test
program, and not just code fragments.

Guest · Posted: Tue Sep 21, 2004 1:17 pm

The code listing that you posted is very simple and indeed it should work. Is simple because the PIC is configured as a MASTER.
In my case the PIC is configured as a SLAVE but when it has something to send over SPI "acts" like a MASTER. As I said the SPI is used for inter-processor communication. The bus access is guarded by a flip-flop and each processor has a line out to signal a new message.

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

Well, if you want me to work on it, you'll have to post a
small test program.