In the latest batch of my stepper controller boards there were two where I had problems programming them. The propeller tool tells me "RAM checksum error" when I hit F10 or F11. What could be the possible cause of this?
There are two propellers on the board which share one EEPROM and the P28..31 signals. But I verified that the second is held in reset while the first is being programmed. Both props also share the same clock but I think that doesn't matter because they run in RCFAST mode while being programmed. Supply is stable at 3.29V. It's a two layer SMT board with the bottom layer as almost solid ground plane. I have four 0.1µF caps near the supply pins at each prop. I don't see any obvious soldering error. If the EEPROM was broken, I think, it should say "EEPROM error" instead of "RAM". I use the original prog-plug from Parallax.