PIC checker

[kyru27]

I'd like to know if something like that exists, as I'm currently having strange results on several pins of the PIC I'm working with (2 V or 0 V) where there should be 5 V, I've checked the circuit and it seems that what is failing is the PIC (although I can program it without problems with the programmer), but perhaps I'm missing something.

Maybe there's some type of software that you can connect your programmer with (in my case a Pickit2 clone) and checks that the PIC is right (basically tests that every PIN is working properly) but I haven´t been able to find it, I guess that if you can program a PIC via software this could also be possible with the appropiate software.

Regards.

 

[3v0]

Could be that your circuit is drawing too much current. Can you post the schematic and which pins are problematic.

 

[large_ghostman]

i had this problem and mine was a very small short on the pcb i used pickit2 standalone software to do a check and it came up short so thats how i found it but yours may be another reason

 

[kyru27]

3v0: I don't think it's drawing too much current, I've measured the alimentation of the PIC and it's 5,3 V. With only 0.3 V of what it's needed it should work nicely. I cannot find the schematic right now.

Little Ghostman: I'm not sure to have understood you. Did you measure a short in the PCB with the Pickit2 Programmer? How did you do that?

 

[3v0]

alimentation, VCC maybe ?

It is rare that the pic is bad but try a 2nd PIC in the circuit. People always want to blame the PIC and it almost never the problem.

For most PICs each digital IO pin is limited to 25mA but the logic 1 voltage drops below 5V when you exceed 15 or 20mA. It is in the data sheet.

Find the schematic if you want real help.

 

[kyru27]

3v0: I meant Vdd, this is basically the schematic except for the 7-segment display which doesn't mind for the problem (without it results are exactly the same).

To start with Pin RB0 should be 5V but it's instead 2 V and RB5 is 0 V when it should be 5 V (pins are connected via resistors to a Kingbright SCA52-11HWA, so it would display a zero in it).

Anyway, onto the main topic, isn't there any software that can check a PIC is right so I do not have to check all the circuit to see possible failures?

 

[srikanthsamaga]

Check PIC datasheet if pullups are needed for port pins.

 

[Pommie]

You need to describe your problem better. Which pins are causing the problem?

Edit, how do you know it's 2V?

Mike.

 

[Mosaic]

I had this problem a couple weeks ago. Turned out to be a hard to detect short....between 50 to 100 ohms which defeated the DMM continuity check. I had to shot gun it, by removing components in sections. Specifically, I had a 12 mil trace running under a 0805 smd part which had too much solder paste that bridged the trace UNDER the part providing the invisible fault.

There is one s'ware method to try. Presuming a common cathode display.
1) Make all the pins on your port digital hi and verify with a DMM or observe your 7 segment.
2) Pass go to step 3, Fail...all pins not high verify all your TRIS and analog settings, ensure all are digital outputs. Retest (fail = test low pins for shorts to ground etc. No fault = replace PIC)
3) Sequentially drive 1 pin low from b7 to b0. Verify when another pin 'also' goes low. Check for a short between them.

Good luck...took me 6 hours of s'ware debugging (and a PIC replacement before I was convinced of a hard to find electrical PCB fault.

 

[kyru27]

Pommie: I measured it with a polimeter.

I've checked it into a new protoboard (I was still on this) and it keeps the same, so I guess it's not some short on the board.

I'll give a try to Mosaic's checking method.

Thanks.

 

[be80be]

I would post your code PORTB has ADC pins