Other Parts Discussed in Thread: ADS1194
Tool/software:
I've had a prototype board fabricated and as far as I can tell, everything is electrically as specified. The ADS1292R is receiving power and signals from the MCU are making it to the pins of the IC.
However I don't get any response from the ADS1292R. For example here's a scope capture of an attempt to read the chip ID register (signals are CS, MISO, MOSI, CLK, in that order):
The ADS1292R behaves nearly as if it's completely asleep and doesn't send anything back on MISO at all. The only thing that indicates any life is that MISO is being pulled down by something when the SPI transaction begins but I don't know whether that's the MCU or the ADS1292R.
Here's my schematic. I've tried to follow the datasheet and schematics of known-working circuits as closely as possible.
AVDD is 3.3V and DVDD is 1.8V. The resistor array with the pullups/pulldowns is 10kΩ.
Both power supplies are pretty clean on the oscilloscope. Transients are infrequent and limited to ±10mV.
The MCU waits 500ms after its own power up before it attempts to communicate with the ADS1292R. It sends the RESET opcode, waits 4-5ms, sends SDATAC, then attempts to receive the chip ID.
At the moment my best guess as to what might be wrong is that I've misunderstood the PWDN/RESET, START or CLKSEL pins. e.g. is it wrong to put pullups on PWDN/RESET and CLKSEL?
Or have I got the command bytes wrong?
