Unable to communicate: Xmit/Receive

[wjt]

I am having communication problems using USB-ICP-LPC9xx flash programmer for the P89LPC924 parts. I am using the 7.373 mhz internal oscillator. One board programmed all the time and 3 other boards give the referenced communication error - no shorts or opens on the boards. Problem is when reading the uP signature. Where to start? It looks like 3 bad uP (unlikely). One board would program intermittently.

Did some more experimenting--- cleaned the board with alcohol changed the Flash Magic oscillator frequency to 14 mHz and read signature as: 00 00 00. Then back to 7.2mHz and it read signature correctly and it programmed.

Changed uP on 2nd board to P89LPC925 (and Flash Magic). Washed board with alcohol and tried various oscillator frequencies. At times a signature reading would occur and then it started timeout and no communication error would pop up.

3rd board was programmed once but now won't even read signature (LPC924). Added 10k pullup on reset pin on uP. Seems it doesn't go into the timeout mode but just says it can't communicate regardless of the Flash Magic oscillator frequency setting. Some LEDs on board indicate the board does reset but then continues to run old program. It should stop running the old program when signature is read. Maybe a problem with FDI programmer.

wjt

[Andy Ayre]

So one board works all the time and the other three have various communication problems? If all four boards are from the same batch, i.e. have the same design, then I would look for solder problems.

Try putting a scope on the ICP signals and compare the signals for the working board with the non-working ones. I would expect to see some kind of difference. Start by looking at the ICP signals at the microcontroller pins then at the FDI hardware.

Andy