I have a bunch of boards (own design) with which I’m not able to communicate using SPI at all. So unable to burn a bootloader. No comms using a mega as a programmer or using an AVR Dragon.
there is continuity (< 2Ohms) between the mega/dragon pins and the mosi/miso/sck of the target. Reset on the target connected to pin 10 on the mega and the reset pin on the ISP connectors on the avr dragon.
reset on the target pulled up to VCC via 10kOhm.
tried 8 boards … all the same.
I’m quite sure that I’m missing something terribly obvious though! Any pointers gratefully received.
the schematic is below.
the intent is to run this board at about 2.6v using the internal oscillator only.
you’ll see that the thermistor signal is both seemingly pulled up and pulled down. this is to allow a digital sensor or a thermistor to be used. in practice I am using only a thermistor so just the pull down (R7) is installed. U1 is not present, the VCC and thermistor holes are used for the thermistor.
I have tried the boards with and without the radio module installed.