Problem with 16F88 controlling h-bridges

[silentwol]

Hi,

I'm using PBP to create a pen plotter. I have made 6 h-bridges to control 3 stepper motors all of which seem to be functioning correctly. I had 4 of the h-bridges plotting when driven by a PICAXE (using an 18X - which is a pre-programed 16F88). I have since switched over to PBP and added an extra two bridges for pen up and down control.

I developed the PIC software using a breadboard and a set of LED's, making sure that the LEDs blink in the right order... this is now finished and working well, receiving data from the computer serial port and flashing accordingly.

However, when I come to plug the PIC into the circuit with the h-bridges, nothing happens. I've checked for shorts over and over again and can't seem to come up with anything... The only differences between the breadboard and veroboard with the h-bridges is that I have 100uF decoupling capacitor and a 4.7K pullup on RA5 on the veroboard. I can't think that these are the problem, and I added a cap and resistor to the breadboard and things seemed to be OK. However, I do remember that the first time I added the decoupling cap to the breadboard, the PIC behaved badly for a few seconds beforing settling down.

Any ideas what the problem could be? I've tried preprograming a routine of pulses so that the PIC isn't depending on the serial input. That still didn't work. It's as if the PIC simply isn't starting up.

Final question is with pin RA5. I wanted to use it as an input for the serial comms, but I couldn't get it working. I've set MCLR off, but it doesn't want to play ball. Any ideas what I could be doing wrong?

Thanks for your help... I'll go back to checking for shorts for the hundredth time