How to sample continuously in IIO, but without a trigger per scan set?

How to sample continuously in IIO, but without a trigger per scan set?

[Leon Woestenberg]

Hello all,

my first endeavours with IIO began with the requirement to sample a
4-channel SPI ADC at 10 kHz rate with accurate periodicy, lowest
jitter and lowest CPU usage.

I first adapted the SPI master to use the hardware DMA capability for
cyclic transfers from the SPI controller. This fulfills the above
requirements, any other approach would introduce too much jitter,
pause in sample trains, or too much CPU overhead.

Then I started working on the IIO driver to use the above. Then I got stuck.

After a trigger, I would like to capture for a large period of time,
with a fixed sampling frequency, not via a software scheduled trigger
per scan. I.e. any trigger (if at all) should start a continuous
capture.

How can I do this in IIO?

I only see calls of a single scan (4 channels, 16-bits per channel) to
my trigger handler; this induces too much overhead.


Regards,

Leon.