Quote Originally Posted by mackrackit View Post
Do you have capacitors across VDD and VSS??
My board is pretty standard with the ICSP pins and a 10k pullup on MCLR pin.

It is powered by a 7805 100ma reg from a 12v bench psu. 1000uf on each side of reg + 0.1uf on vdd/vss pins of 16f88. I tried adding extra cap 10uf tantalum across vdd/vss no change. Are my 1000uf a bit big?

Tried powering it from a 9v battery via reg. No apparent change.

Connections checked on board using pickit2 software and it is supplying the correct voltages inc 12v on MCLR under trouble shooting mode.

The chip does work in the board when programmed off board and is communicating as per my current software.

Once every few trys it will communicate briefly but always reports errors or can't find device.

Once the chip is running in the board I can't communicate with it. If I insert it blank into the board I can communicate initially but it does not program sucessfully and then I loose comms and have to erase it in my other programmer and program it with that!

The board looks like this.

http://www.solarvan.co.uk/bcm/fakebcm004.jpg

My untidy schematic here.

http://www.solarvan.co.uk/bcm/BATTSC..._INTERFACE.jpg

I appreciate the help thanks.