Just a quick note incase anyone else ever runs into this...

The BB/TI ADS1216 ADC chip (which is pretty cool) has a data sheet so terse
that it has been quite a challenge to interpret it correctly even with the
FAE to help.

One issue is that since our current project was starved for IO (when isn't
that the case?) we decided not to use the hardware /DRDY line to check for
when the chip is busy doing stuff. Instead, we would just poll the status
register via the SPI port and check the /DRDY bit in that register which is
a mirror of the hardware line (as per the datasheet). 

Except that it turns out that during the self calibration procedure the chip
stops responding to the SPI port at all. The microcontroller then interprets
this as a status register with all bits zero including the /DRDY bit. If
they had given me a DRDY bit rather than a /DRDY bit all would be well, but
since 0 means ready rather than 1... The PIC sees the 1216 as being ready to
go and immediately starts trying to take ADC readings.

This was really hard to debug since if you single step, there is lots of
time between the self cal command and the first status check for the chip to
complete the cal and not show the bug. You single step and all is well, you
run it and all the readings come back zero...

Luckily, there is another bit in the status register that needed to be a one
for our application (Unipolar vice Bipolar data format) so I was able to
interpret a status of all zeros as a "chip is ignoring me and is not ready"
and we avoided a hardware change / re-design.

And the datasheet does NOT say anything about the SPI port being ignored
during calibration... Maybe that is some sort of standard or expected
behavior to others, but I hadn't seen it before. This may also be the case
on the ADS 1240 and others of its family.

---
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