Fibre optic transmission system errors

[DrWhoF]

I have a problem with a system where I have a 87C51 microcontroller reading a small keypad, then fibre optic data transmission system and at the other end another 87C51 executes commands,
Problem occures after unpredicted time: the top end stops sending commands.
How can I find out why?
DrWhoF

 

[IanP]

Re: Fibre optic data

If you have an oscilloscope start with the 87C51 TX pin, then go to the input of the fibre optic modem, and so on.
By doing this you will find out where the commands are stopped, or not generated at all - if the mcu is faulty..
It looks for me like a thermal fault, so you can arm yourself with a heatgun and a freazing spray.
Heat up crucial components in your circuit and simulate this fault .. again, start with the 87C51 ..
Regards,
IanP

 

[DrWhoF]

Re: Fibre optic data

This idea with heating and cooling was very good.
That was 87C51 which caused the problem.
Thank you very much.
DrWhoF