I am using the MAX31856 digital thermocouple amplifier on the Adafruit backpack board coupled with a PIC16F1783.

SPI works and can read all of the device's registers. However, the device seems to be locked up in "interrupt" mode. Reads of all the registers show default values and no pending faults.

Anyone have experience unlocking that chip? I tried the datasheet way of writing to FAULTCLR without success.

 

SOLVED
Apparently the default is to do nothing. After messing with the registers and trying to create a fault, I set bit 7 of Reg 0x00 to allow periodic readings, and it came to life (reads about every 100 ms and DRDY bit works). Adafruit's code is all in arduino C. I don't know whether that code does that.

This statement (emphasis added) in its brochure:

DRDY - This pin is used for advanced uses where you tell the sensor to begin a reading and then wait for this pin to go low. We don't use it in our library code because we keep it simple with a delay/wait, but it is available in case you need it!

caused me to assume that activating DRDY for periodic readings was not necessary.

This is the second time I have been caught by a device with a default state of being off. (The first time was the BMC156 accelerometer and compass.)