Hi all
I am not sure whether this is the right place to bring up this issue. Still i am posting this so that people could share their experience and throw some light on possible cause for this intermittent issue.
In our custom board using DM8148, some of the setups (2 out of 14) has an intermittent bar-code issue. The bar code reader is a module with UART interface for transferring data from the module to the DM8148 on successful bar-code reading. The module is controlled by two control signals - (i) Power Enable and (ii) Trigger. Power enable signal brings out the module from power down mode back to normal operating mode and Trigger is issued 300ms after Power Enable is activated. The path taken by signals are Main PCBA-->Cable Harness-->Another Sub- PCBA-->FFC-->Barcode Module.
The issue we face is that of intermittent bar-code reading occasionally. It is very random and happens once in few weeks - the systems are running tests every work day. Power cycling does not help most of the times. The interesting part is whenever the issue props up and i hook up the probes to the two control lines, the things starts working and then no matter what we try, it continues to work after the probes are removed. hence we are unsure how to reproduce this issue.
We have followed all guidelines of the bar-code manufacture with respect to the interfacing and also with the control signal issuance for the module
Since these are not exactly high speed interfaces, what is causing the issue? The signals 'look' clean on normal operation. Would adding a capacitor of around 22pF to ground solve this intermittent issue? (I am assuming the probe is presenting a capacitve load to the lines). Even if that is the case, what could be the possible root cause?
Suggestions and inputs welcome! Thanks :)
Regards,
KS
