Hang up on pic17c756 with external bus

[juan_manuell]

Hi, I have finished an equipment with a pic17c756 working in extended mode (microprosesor and microntroller). My problem is when i plug / unplug the transformer my equipment hang up.
I conected it to battery and disconnet transformer from board and when i plug /unplug from line the equipment hang up.

Well this toldme that some electromagnetic flow hang my board.
I download the cristal from 16Mhz(bus 4Mhz) to 4Mhz (bus 1Mhz). And still hang on.

I dont know what i could do, to solve this problem.
I tell to my boss to shield the transformer but this is not cheap

If any have some advise or were i could read about how to desing microprocesor bus.

Thanks in advance

 

[C-Man]

juan_manuell,

is your watchdog and brownout detect enabled?

Do you have external inputs which are directly connected to the processor and are connected to you board via wires?

I would suspect that you are catching some spikes via your inputs or supply.

Check decoupling of inputs and supply.

best regards

 

[juan_manuell]

Hi C-Man

is your watchdog and brownout detect enabled?

Yes both are enabled

Do you have external inputs which are directly connected to the processor and are connected to you board via wires?

No, some sensor past trought opto´s and my keyboard pass throght encoder

I would suspect that you are catching some spikes via your inputs or supply.

I was thinking on bus in that case, and in all supply i put 0.1 uF to decoupling

Check decoupling of inputs and supply.

Could you recomend me some methods

Thanks for your help

 

[C-Man]

If the watchdog is enabled and your program is still hanging I would carefully inspect where the watchdog is reset in your program.

You should do this only in a few routines, if you reset the watchdog too often you might be hanging for example in a loop where the watchdog gets reset but your program hangs there.

I once had a situation with a dataflash from Atmel where SPI communication did hang when a relais (which switched a motor) was switched on. Carefully selecting where the watchdog gets reset could at least trap this situation.

Not very easy to give you a good advice here, too many variables ...

Maybe you can try to connect no or as few as possible external sensors to your board and check if this makes a difference.

Also check if you have any unconnected (floating) pins on your processor they can do a low of harm in EMI situations.

best regards

 

[juan_manuell]

Hi

If the watchdog is enabled and your program is still hanging I would carefully inspect where the watchdog is reset in your program.

Sorry, i forget to tell that when started to hang i enable the WDT and make some checks and the soft restart. But the problem is that this condittion it is not acepted

I leave from the board the external ram, RTC on I2C bus.

The problem is that graphical display 240*64 hang too and micro still running. unique solution turn on device.

Not very easy to give you a good advice here, too many variables ...

I know, thanks in advance for you help

Also check if you have any unconnected (floating) pins on your processor they can do a low of harm in EMI situations.

best regards

Ohh.. I forget that i have someones floating and 2 are a/d inputs.
Maybe this could be.

Thanks again

 

[juan_manuell]

Hi to all,
The solution for the noise was, put a piece of copper to shield the copper layer were is the bus of microontroller. And this result the best solution