Light sensor on the CPX
The Circuit Playground (Classic, Express and Bluefruit) has an on-board ambient light sensor. The Circuit Playground software library handles the low-level details and the CircuitPlayground.lightSensor() function returns an 10-bit integer (\(0\le v \le 1023\)), where a value of \(v\sim300\) corresponds to a well lit office environment
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Light Sensor
The Circuit Playground Express has an ambient light sensor mounted permanently to the circuit board as shown in the following image.
Reading the Light Sensor with Hello_LightSensor
The Hello_LightSensor sketch is part of the Adafruit Circuit Playground library. You can open the sketch by selecting File –> Examples –> Adafruit Circuit Playground –> Hello_CircuitPlayground –>Hello_LightSensor. Running the sketch produces light sensor readings in the Serial Monitor.
Light sensor reading scale
Consult the source code in Hello_LightSensor to see how ambient light readings are made.
The reading of the light sensor is obtained with the statement
value = CircuitPlayground.lightSensor();
where value is an int. The reading is an 8-bit value, i.e. an integer in the range between 0 and 1023, where 0 is completely dark and 1023 is the maximum brightness the sensor can record. Typical ambient light levels are about 300 on this scale.