Analog Input - ADC

Board	External signals	Precision	Reference voltage**
iMX6 SoloX COM	8 signals divided into 2 channels each with 4 inputs	12 bit	3.3V
iMX6 Quad COM	Not supported
iMX6 DualLite COM	Not supported
iMX6 UltraLite COM*	10 signals divided into 1 channel with 10 inputs	12 bit	3.3V
iMX7 Dual COM	8 signals divided into 2 channels, each with 4 inputs	12 bit	1.8V
iMX7 Dual uCOM	4 signals divided into 1 channel with 4 inputs	12 bit	1.8V
iMX7ULP uCOM	Not available in U-Boot and Linux
iMX8M Quad COM	Not supported
iMX8M Mini uCOM	Not supported
iMX8M Nano uCOM	Not supported
iMX93 uCOM	4 signals divided into 1 channel with 4 inputs	12 bit	1.8V

^* - To use the ADC channels on iMX6 UltraLite they must first be configured and enabled in the device tree. The scope of how to do that is beyond this document.
^** - Note that input voltages above max will damage the CPU.

U-Boot

Not currently available.

Linux

Each ADC channel will be represented by a iio:device node in the file system.

ls /sys/bus/iio/devices/

iio:device0 iio:device1

ls /sys/bus/iio/devices/iio\:device0/

buffer name
dev                             of_node
in_conversion_mode              power
in_voltage0_raw                 sampling_frequency_available
in_voltage1_raw                 scan_elements
in_voltage2_raw                 subsystem
in_voltage3_raw                 trigger
in_voltage_sampling_frequency   uevent
in_voltage_scale

In this case (iMX6 SoloX) the 8 signals are divided into two channels (iio:device0 and iio:device1) of 4 inputs each (in_voltage0_raw, in_voltage1_raw, in_voltage2_raw and in_voltage3_raw).

To read the raw value (range is 0 - 4095 for 12 bit precision).

cat /sys/bus/iio/devices/iio\:device0/in_voltage2_raw

302

To see the scale.

cat /sys/bus/iio/devices/iio\:device0/in_voltage_scale

0.805664062

To get the actual value multiply the raw value and the scale: 302 * 0.805664062 = 243.3 mV.