Problem with two pics

Markdem · Joined: 24 Jun 2005 Posts: 206

Hi All, i have a small problem. I am tring to get I2C communications between two pic. I have done this before with two PIC16F887A chips, but in this project i would like to use a PIC16F887A and a PIC16F88. Problem is the PIC16F88 will stop if it is connected to the same power rail as the PIC16F887A. as soon as i disconnect it, the PIC16F88 will start running again.
The code on both the PICs is just flashing a led, nothing to do with I2C yet.
Both PICs are running a 20Mhz external cristal with 22pf caps going to ground. Voltage on the rail is 5v even with both PICs connected.

Anyone have any ideas that i can try

Thanks you very much

mark

kender · Joined: 09 Aug 2004 Posts: 768 Location: Silicon Valley

The only thing that comes to mind is that there is not enough current for both PICs and the rest of your circuitry. If you supply more cuurent, does the problem go away?

Markdem · Joined: 24 Jun 2005 Posts: 206

Thanks kender. i checked the current draw, but t is only 80mA, and the power supply is rated to 3A. The think i have noticed is that the led connected to the second PICF88 does not go off. It will stay on untill i disconnect the PIC16F887A.

Any more ideas

Thanks, Mark

Markdem · Joined: 24 Jun 2005 Posts: 206

Hi All, this is doing in my head. I have now built another test rig, but this time using 2 PIC16F887A chips. Works without a problem. Do you think is could be a faulty PIC16F88?? I have checked for shorts on the other circurt, but cant find anything that is wrong. Also, i would like to check if the cyristal is still ticking, but i dont have a scope. Does anybody use a PC baced scope, and how are they.

Thanks, mark

kender · Joined: 09 Aug 2004 Posts: 768 Location: Silicon Valley

Markdem · Joined: 24 Jun 2005 Posts: 206

Hi Kender, i have got two crystals, one for each of the PICs. Funny think i have now found. The first rig hag 2 ds1830 temp probe connectors on it, bu the probes where not connected. This new rig does not. When i reconnected the connectors, the problem came back, again with no ds1830 connected. Why would some wire pulled up be making the pics lock up??

Thanks, Mark

kender · Joined: 09 Aug 2004 Posts: 768 Location: Silicon Valley

Guest · Posted: Sun Mar 12, 2006 8:37 pm

HAHA sorry, I know thats an easy enough mistake and well all make them but that funny as hell!