I have a PCB with an ICSP header for programming. At first everything was fine and I could program the uC perfectly. However, from one minute to the next, I cannot read the uC.
The ISP programmer works. I can read the signature from a different uc on a different board
I triple checked the pcb traces but I cannot find anything wrong with them
I tried different c's around my crystal
The uC itself is still operational
Lowered the reset pullup resistor
Maybe the sensor I added along the way which uses SPI troubles the programming?
SuperR:
Maybe the sensor I added along the way which uses SPI troubles the programming?
Any ideas?
Anything connected to the SPI lines can cause problems. Make sure you have a pullup on the CS line for the device so it keeps quiet while you're programming.
pepe:
Normally, the modification of the "SPI programming enable" Fuse requires a parallel programming. But the "External Reset disable" Fuse could have been altered.
Thanks for reminding me, I had forgotten it cannot be altered by SPI.
-I replaced the uC with different uC's in the same position and those are unreadable too. I therefore think it is not caused by a wrong fuse of lock bit.
update; If I place a uC in it, it runs well. It reads over i2c and SPI en spits out data over rs232 via a max232
-Unfortunatly, it is quite tricky to disconnect the added sensor.
update; It worked for a while with the added sensor. At some point it killed my pc and stopped working
-I think I dit not use a pullup on the CS line of the sensor.
update; Tried puling it up but with no better results
-For comparison, I will populate another of my uC 'motherboard PCB's' and try and see at what alteration the uC can no longer be read.
update; That'll require an order from rsonline/farnell. More on this,, next week.