Analog Inputs (ADC) (MX-4)

Overview

The ADC conversions are managed by the co-processor and the values are exposed as sysfiles.

• C61
  • input_voltage
  • analog_1
  • analog_2
  • Start signals
  • More information see IIOs
• CT and CT GL
  • input_voltage
  • input_battery
  • analog_1 (start signal, analog in 1A&B)
  • analog_2 (4-20mA)
  • analog_3 (0-32V)
  • analog_4 (0-32V)
  • Start signals
• T20, T30 and T30 FR
  • input_voltage
  • input_battery
  • analog_1
  • Start signals

# ls /opt/hm/pic_attributes/ | grep -i analog
analog_1_calibration_u
analog_1_uA
analog_2_calibration_u
analog_2_uA
analog_3_calibration_u
analog_3
analog_4_calibration_u
analog_4
root@mx4-gtt:~# ls /opt/hm/pic_attributes/ | grep -i input
input_battery_calibration_u
input_battery
input_battery_threshold_high
input_battery_threshold_low
input_temperature_calibration_u
input_temperature_mC
input_voltage_calibration_u
input_voltage
input_voltage_threshold_high
input_voltage_threshold_low

Calibration files are not be used by end users.

Example reading input voltage

cat /opt/hm/pic_attributes/input_voltage
14917

Example of when Vref (ADC reference voltage) is turned off.

Vref should normally be always on but it is turned off when entering sleep (go_to_sleep.sh). If you poll ADC values while entering sleep you will get some errors after Vref has been turned off. Note: Coprocesssor firmware 2.8.2 and later (CT and T30/T30 FR) vref and other power are turned off after main processor by the coprocessor so it should not be any errors even in late state of go_to_sleep.sh.

# echo 0 > /sys/class/gpio/gpio243/value
# cat /opt/hm/pic_attributes/input_voltage
cat: read error: Operation not permitted