Re: Reading ADC that comes from a multiplexer

[Fabio Estevam <festevam@gmail.com>]

Hi Peter,

On Wed, Sep 22, 2021 at 4:27 AM Peter Rosin <peda@axentia.se> wrote:

> Basically, the whole point is that you simply don't. The iio-mux exposes
> the channels as 8 new ADCs, and whenever you read a value from one of
> them, the iio-mux operates the gpios for you, giving you the impression
> that you have 8 independet ADCs. They are of course not independent, but...

Thanks for the clarification. It was helpful.

> That's exposed to user-space as:
>
> $ ls "/sys/bus/iio/devices/iio:device3"
> in_altvoltage2_compare_interval  in_altvoltage5_scale
> in_altvoltage2_invert            in_altvoltage6_compare_interval
> in_altvoltage2_raw               in_altvoltage6_invert
> in_altvoltage2_scale             in_altvoltage6_raw
> in_altvoltage3_compare_interval  in_altvoltage6_scale
> in_altvoltage3_invert            in_altvoltage7_compare_interval
> in_altvoltage3_raw               in_altvoltage7_invert
> in_altvoltage3_scale             in_altvoltage7_raw
> in_altvoltage4_compare_interval  in_altvoltage7_scale
> in_altvoltage4_invert            name
> in_altvoltage4_raw               of_node
> in_altvoltage4_scale             power
> in_altvoltage5_compare_interval  subsystem
> in_altvoltage5_invert            uevent
> in_altvoltage5_raw
> $ cat "/sys/bus/iio/devices/iio:device3/name"
> envelope-detector-mux

Ah, so that's my issue then. I don't see a new device inside
/sys/bus/iio/devices/.

I only see the original stmpe ADC:

ls "/sys/bus/iio/devices/iio:device0"
dev              in_voltage5_raw  in_voltage_scale  power
in_temp8_input   in_voltage6_raw  name              subsystem
in_voltage4_raw  in_voltage7_raw  of_node           uevent

Maybe my dts is not correct to make the mux appear under
/sys/bus/iio/devices/iio:device1.

Here is my dts that shows more context with the STMPE811 ADC:
https://pastebin.com/raw/7Nn2aAtN

stmpe811 is an mfd device that can be used as a touchscreen and as a normal adc.

I only use the adc functionality.

Any suggestions are welcome.

Thanks,

Fabio Estevam