Letux Kernel


You are looking at an old revision of the page Sensors. This revision was created by Nikolaus Schaller.

Table of Content

How to access the Sensors

Unless noted otherwise, the sensors are low power devices and always enabled.

3-Axis Accelerometer

cat /sys/bus/i2c/drivers/tsc2007/2-0041/coord

Data range: 1g is approx. equivalent to a readout of 4096. The maximum is 4g, i.e. 16383. If the device is rotated by 180 degrees, the values become negative.

The axis orientation is:

  • x:
  • y:
  • z:

3-Axis Gyroscope

cat /sys/bus/i2c/devices/i2c-2/2-0068/values

3-Axis Compass

Enable power

The nominal analog voltage of the chip should be 2.5 V

echo "2500000" >/sys/devices/platform/reg-virt-consumer.2/max_microvolts echo "2500000" >/sys/devices/platform/reg-virt-consumer.2/min_microvolts echo "normal" >/sys/devices/platform/reg-virt-consumer.2/mode

disable power

echo "0" >/sys/devices/platform/reg-virt-consumer.2/max_microvolts

Barometer and Thermometer

cat /sys/bus/i2c/devices/i2c-2/2-0077/pressure
cat /sys/bus/i2c/devices/i2c-2/2-0077/temperature

Touch Screen Position, Pressure/Resistance, Temperature and (optional) Ambient light intensity

The raw ADC values, plate resistance, the temperature sensors and the AUX input (optional ambient light sensor) can be read through

cat /sys/bus/i2c/drivers/tsc2007/2-0048/values

The order of the values is

x, y, pressure, pendown(0/1), z1, z2, temp0, temp1, aux, resistance

The temp and aux values are updated every 100ms and the other values only on pen-down every 1ms.

Pressure values are an estimate and are lower for touches with small area (fingernail, stylus) and higher for bigger touch area (finger tip or multitouch). Typical range:

  • 300 for stylus
  • 700 for finger tip
  • 2000-15000 for two fingers

Resistance is an estimate with a reference value of 600 Ohms.

Note: the x and y values are the raw values before any calibration (which is usually done through libts or similar means).