Microbit and TSL2591 light-to-digital converter example
In this article we look at another light-to-digital converter – this time its the TSL2591 and we will connect it to our Microbit
First lets look at the sensor
The TSL2591 is a very high sensitivity light-to-digital converter that transforms light intensity into a digital signal output capable of direct I2C interface. The device combines one broadband photodiode (visible plus infrared) and one infrared-responding photodiode on a single CMOS integrated circuit.
Two integrating ADCs convert the photodiode currents into a digital output that represents the irradiance measured on each channel.
This digital output can be input to a microprocessor where illuminance (ambient light level) in lux is derived using an empirical formula to approximate the human eye response. The TSL2591 supports a traditional level style interrupt that remains asserted until the firmware clears it
Features
- Highest sensitivity to 188µLux
- Patented dual-diode architecture
- 600M:1 dynamic range
- Programmable interrupt function
- UV-rejection package
This is the breakout I bought
Parts Required
Once again for ease of use I connect an expansion board to the microbit, I feel this makes it easier to connect to a sensor like the one pictured above using connecting wire
Schematic/Connection
Code Example
This uses the library from https://github.com/adafruit/Adafruit_TSL2591_Library
This is the default example
[codesyntax lang=”cpp”]
/* TSL2591 Digital Light Sensor */ /* Dynamic Range: 600M:1 */ /* Maximum Lux: 88K */ #include <Wire.h> #include <Adafruit_Sensor.h> #include "Adafruit_TSL2591.h" // Example for demonstrating the TSL2591 library - public domain! // connect SCL to I2C Clock // connect SDA to I2C Data // connect Vin to 3.3-5V DC // connect GROUND to common ground Adafruit_TSL2591 tsl = Adafruit_TSL2591(2591); // pass in a number for the sensor identifier (for your use later) /**************************************************************************/ /* Displays some basic information on this sensor from the unified sensor API sensor_t type (see Adafruit_Sensor for more information) */ /**************************************************************************/ void displaySensorDetails(void) { sensor_t sensor; tsl.getSensor(&sensor); Serial.println(F("------------------------------------")); Serial.print (F("Sensor: ")); Serial.println(sensor.name); Serial.print (F("Driver Ver: ")); Serial.println(sensor.version); Serial.print (F("Unique ID: ")); Serial.println(sensor.sensor_id); Serial.print (F("Max Value: ")); Serial.print(sensor.max_value); Serial.println(F(" lux")); Serial.print (F("Min Value: ")); Serial.print(sensor.min_value); Serial.println(F(" lux")); Serial.print (F("Resolution: ")); Serial.print(sensor.resolution, 4); Serial.println(F(" lux")); Serial.println(F("------------------------------------")); Serial.println(F("")); delay(500); } /**************************************************************************/ /* Configures the gain and integration time for the TSL2591 */ /**************************************************************************/ void configureSensor(void) { // You can change the gain on the fly, to adapt to brighter/dimmer light situations //tsl.setGain(TSL2591_GAIN_LOW); // 1x gain (bright light) tsl.setGain(TSL2591_GAIN_MED); // 25x gain //tsl.setGain(TSL2591_GAIN_HIGH); // 428x gain // Changing the integration time gives you a longer time over which to sense light // longer timelines are slower, but are good in very low light situtations! //tsl.setTiming(TSL2591_INTEGRATIONTIME_100MS); // shortest integration time (bright light) // tsl.setTiming(TSL2591_INTEGRATIONTIME_200MS); tsl.setTiming(TSL2591_INTEGRATIONTIME_300MS); // tsl.setTiming(TSL2591_INTEGRATIONTIME_400MS); // tsl.setTiming(TSL2591_INTEGRATIONTIME_500MS); // tsl.setTiming(TSL2591_INTEGRATIONTIME_600MS); // longest integration time (dim light) /* Display the gain and integration time for reference sake */ Serial.println(F("------------------------------------")); Serial.print (F("Gain: ")); tsl2591Gain_t gain = tsl.getGain(); switch(gain) { case TSL2591_GAIN_LOW: Serial.println(F("1x (Low)")); break; case TSL2591_GAIN_MED: Serial.println(F("25x (Medium)")); break; case TSL2591_GAIN_HIGH: Serial.println(F("428x (High)")); break; case TSL2591_GAIN_MAX: Serial.println(F("9876x (Max)")); break; } Serial.print (F("Timing: ")); Serial.print((tsl.getTiming() + 1) * 100, DEC); Serial.println(F(" ms")); Serial.println(F("------------------------------------")); Serial.println(F("")); } /**************************************************************************/ /* Program entry point for the Arduino sketch */ /**************************************************************************/ void setup(void) { Serial.begin(9600); Serial.println(F("Starting Adafruit TSL2591 Test!")); if (tsl.begin()) { Serial.println(F("Found a TSL2591 sensor")); } else { Serial.println(F("No sensor found ... check your wiring?")); while (1); } /* Display some basic information on this sensor */ displaySensorDetails(); /* Configure the sensor */ configureSensor(); // Now we're ready to get readings ... move on to loop()! } /**************************************************************************/ /* Shows how to perform a basic read on visible, full spectrum or infrared light (returns raw 16-bit ADC values) */ /**************************************************************************/ void simpleRead(void) { // Simple data read example. Just read the infrared, fullspecrtrum diode // or 'visible' (difference between the two) channels. // This can take 100-600 milliseconds! Uncomment whichever of the following you want to read uint16_t x = tsl.getLuminosity(TSL2591_VISIBLE); //uint16_t x = tsl.getLuminosity(TSL2591_FULLSPECTRUM); //uint16_t x = tsl.getLuminosity(TSL2591_INFRARED); Serial.print(F("[ ")); Serial.print(millis()); Serial.print(F(" ms ] ")); Serial.print(F("Luminosity: ")); Serial.println(x, DEC); } /**************************************************************************/ /* Show how to read IR and Full Spectrum at once and convert to lux */ /**************************************************************************/ void advancedRead(void) { // More advanced data read example. Read 32 bits with top 16 bits IR, bottom 16 bits full spectrum // That way you can do whatever math and comparisons you want! uint32_t lum = tsl.getFullLuminosity(); uint16_t ir, full; ir = lum >> 16; full = lum & 0xFFFF; Serial.print(F("[ ")); Serial.print(millis()); Serial.print(F(" ms ] ")); Serial.print(F("IR: ")); Serial.print(ir); Serial.print(F(" ")); Serial.print(F("Full: ")); Serial.print(full); Serial.print(F(" ")); Serial.print(F("Visible: ")); Serial.print(full - ir); Serial.print(F(" ")); Serial.print(F("Lux: ")); Serial.println(tsl.calculateLux(full, ir), 6); } /**************************************************************************/ /* Performs a read using the Adafruit Unified Sensor API. */ /**************************************************************************/ void unifiedSensorAPIRead(void) { /* Get a new sensor event */ sensors_event_t event; tsl.getEvent(&event); /* Display the results (light is measured in lux) */ Serial.print(F("[ ")); Serial.print(event.timestamp); Serial.print(F(" ms ] ")); if ((event.light == 0) | (event.light > 4294966000.0) | (event.light <-4294966000.0)) { /* If event.light = 0 lux the sensor is probably saturated */ /* and no reliable data could be generated! */ /* if event.light is +/- 4294967040 there was a float over/underflow */ Serial.println(F("Invalid data (adjust gain or timing)")); } else { Serial.print(event.light); Serial.println(F(" lux")); } } /**************************************************************************/ /* Arduino loop function, called once 'setup' is complete (your own code should go here) */ /**************************************************************************/ void loop(void) { //simpleRead(); advancedRead(); // unifiedSensorAPIRead(); delay(500); }
[/codesyntax]
Output
Open the serial monitor and you should see something like this
Starting Adafruit TSL2591 Test!
Found a TSL2591 sensor
————————————
Sensor: TSL2591
Driver Ver: 1
Unique ID: 2591
Max Value: 88000.00 lux
Min Value: 0.00 lux
Resolution: 0.0010 lux
————————————
————————————
Gain: 25x (Medium)
Timing: 300 ms
————————————
[ 1287 ms ] IR: 1580 Full: 5023 Visible: 3443 Lux: 128.383667
[ 2217 ms ] IR: 1594 Full: 5123 Visible: 3529 Lux: 132.244583
[ 3147 ms ] IR: 1597 Full: 5136 Visible: 3539 Lux: 132.658463
[ 4077 ms ] IR: 1600 Full: 5145 Visible: 3545 Lux: 132.875839
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