[PIC] PIC18F25K80-I/SS Very strange problem

[aqua_life]

Hello,

First of all I want to thank you everyone that will try to help me solving this problem.
During last years I have been developing projects for Automotive applications using PIC18 products.
Since the projects need CAN communication with the vehicle I have been using PIC18F25K80.
We have simple projects that the PIC only transmit up to 10 CAN messages and when we program 20 PIC´s all of them work correctly.
However we have other project that the PIC has to transmit 15 CAN messages and when we program 20 PIC´s half of them don´t work correctly. The program is always running in the PIC because we have other outputs (i.e. PWM) and these are working however CAN communication just don´t work on half of these.
We already tried to program the PIC again, same result, we already tried to replace all other components on the PCB without success (oscillator, mcp2551, etc).

So, when we program 20 PIC18F25K80-I/SS and we test them only half of them is working correctly on CAN communication.
The PIC´s that aren´t working correctly we use them for other project also with CAN but with less messages and it work perfect.
We have a development board with a 18F25K80-I/SP and during development of projects we never had any problems. So, maybe problem is with I/SS processors and not with I/SP processors.
I sincerelly thought that maybe this batch of processors might be faulty and I ordered 20 PIC18F26K80-I/SS which is very similar only memory size is different and I have the same problem. I program the 20 PIC´s and only half of them work with this program. The others must program with a simpler CAN project to work.

What should I do ? Any ideas ?
Do you know any Microchip technical support contact to ask them if any other customer with these PIC´s has same problem ?

Thanks for your help

 

[KlausST]

Hi,

I guess it´s a software problem.
Maybe when powering up a timing - even for a periferal part - is not clearly deifned.
Maybe a clock frequency problem

Btw: "only half of them work" is no error description. It is meaningless without detailed description.
--> Your software designer need to debug which section of your software is working properly and which section does not work properly.

Klaus

 

[aqua_life]

I have been testing a lot more now and I think we found the problem.
Using a 12 Volt car battery as a power supply the CAN bus communication always work correctly.
And we were testing the system on the bench using a DC Power Supply.
We think this power supply might put some electrical noise on the system and sometimes it doesn´t work correctly.
We will keep testing to make sure this was our problem...

Thanks !

 

[Aussie Susan]

I suspect that you will get a LOT more noise on an automotive power supply than a bench supply.
Susan