I.MX6UL internal ADC
This description uses Linux kernel >= 4.8.
i.MX6UL (processor of OPOS6UL has an integrated 12 bits 16 channels Analog to Digital Converter.
Only channels 0-6 may be used to generic conversions and channels 2, 3, 4, 5 are used for the touchscreen on OPOS6ULDev.
- Channel 1 is available on J21 pin 40 of OPOS6ULDev (AIN1/YNLR: muxed with touchscreen)
- Channel 2 is available on J21 pin 38 of OPOS6ULDev (AIN2/YPLL: muxed with touchscreen)
- Channel 3 is available on J21 pin 39 of OPOS6ULDev (AIN3/XNUR: muxed with touchscreen)
- Channel 4 is available on J21 pin 37 of OPOS6ULDev (AIN4/XPUL: muxed with touchscreen)
- Channel 8 is available on J3 pin 12 of OPOS6ULDev (AIN8)
- Channel 9 is available on J3 pin 7 of OPOS6ULDev (AIN9)
Driver is by default included if you choose an OPOS6UL as target.
Otherwise, you can select it that way:
[ ] $ make linux-menuconfig
Device Drivers ---> ... <*> Industrial I/O support ---> ... Analog to digital converters ... <*> Freescale vf610 ADC driver
Then compile the distribution :
[ ] $ make linux && make
Read channels value
# cd /sys/bus/iio/devices/iio:device0 # ls buffer in_voltage5_raw current_timestamp_clock in_voltage6_raw dev in_voltage7_raw in_conversion_mode in_voltage8_raw in_temp_input in_voltage9_raw in_voltage0_raw in_voltage_sampling_frequency in_voltage10_raw in_voltage_scale in_voltage11_raw name in_voltage12_raw of_node in_voltage13_raw power in_voltage14_raw sampling_frequency_available in_voltage15_raw scan_elements in_voltage1_raw subsystem in_voltage2_raw trigger in_voltage3_raw uevent in_voltage4_raw
To read ADC value just «cat» the corresponding input file:
# cat in_voltage1_raw for channel 1 (ADC1_IN1) 4095
All values are not converted (ie. directly show the register content). To have the mV value, you must do: value_mV = read_value * 3300/4095
- You can access this device from your C/C++ application using as_adc_xxx_iio functions from AsDevices
- target/demos/oscillo is a "good" example to start with...