5.9 KiB
MAX44009 I2C LUX sensor
Library for MAX44009 / GY-49 I2C lux sensor.
Description
a.k.a. GY-49
The MAX44009 ambient light sensor is an I2C sensor, that has a 22 bit dynamic range from 0.045 lux to 188,000 lux.
Relates to https://github.com/RobTillaart/Max44007
Schema breakout max44009 / GY-49
// breakout MAX44009 / GY-49
//
// +--------+
// VCC |o |
// GND |o |
// SCL |o o| ADDRESS
// SDA |o o| -INT
// +--------+
//
// ADDRESS:
// 0 = 0x4A
// 1 = 0x4B
//
// INT:
// Connect the INT pin to an pull up resistor
// 0 = interrupt
// 1 = no interrupt
// connect to an LED or an interrupt pin of an Arduino
//
Interface
- enum class Boolean { True, False } enum class to prevent bool to be implicitly casted to int.
Constructor
- Max44009(uint8_t address, uint8_t dataPin, uint8_t clockPin) Constructor with dataPin (sda) and clockPin (scl) for ESP32 and ESP8266.
- Max44009(uint8_t address, begin = Boolean::True) Constructor for other boards e.g. UNO.
- Max44009(begin = Boolean::True) Constructor with default I2C address 0x4A == 74.
- void configure(uint8_t address, TwoWire *wire, begin = Boolean::True) Change I2C interface and address.
- bool isConnected() returns true if the device address configured is available on I2C bus.
Basic
- float getLux() read the sensor and return the value in LUX. If the value is negative, an error has occurred.
- int getError() returns last error.
// ERROR CODES
#define MAX44009_OK 0
#define MAX44009_ERROR_WIRE_REQUEST -10
#define MAX44009_ERROR_OVERFLOW -20
#define MAX44009_ERROR_HIGH_BYTE -30
#define MAX44009_ERROR_LOW_BYTE -31
Configure thresholds
check datasheet for details
- bool setHighThreshold(float value) sets the upper threshold for the interrupt generation (INT pulls LOW). Works only if INTE bit is set by enableInterrupt(). Function returns false if the value is out of range.
- float getHighThreshold() returns the value set.
- bool setLowThreshold(float value) sets the lower threshold for the interrupt generation (INT pulls LOW). Works only if INTE bit is set by enableInterrupt(). Function returns false if the value is out of range.
- float getLowThreshold() returns the value set.
- void setThresholdTimer(uint8_t value) Time the threshold needs to be exceeded, defined in steps of 100ms. 2 seems to be a practical minimum.
- uint8_t getThresholdTimer() returns the value set.
Configure interrupts
check datasheet for details
- void enableInterrupt() enables the upper and lower threshold interrupts.
- void disableInterrupt() disables the threshold interrupts.
- bool interruptEnabled() returns 1 if the interrupt mode is enabled.
- uint8_t getInterruptStatus() returns 1 if an interrupt has occurred.
Configure flags
check datasheet for details
- void setConfiguration(uint8_t) writes directly to configuration register. warning Use with care.
- uint8_t getConfiguration() reads the current configuration register.
Configure sample mode
Check datasheet for details.
CCR = Current Divisor Ratio.
TIM = Integration time.
- void setAutomaticMode() in automatic mode the MAX44009 determines the CDR and TIM parameters.
- void setContinuousMode() continuous mode uses more power than a "single" conversion. Advantage is that the latest data is always available fast.
- void clrContinuousMode() uses less power so better for LOW power configurations.
- void setManualMode(uint8_t CDR, uint8_t TIM) Set the Current Divisor Ratio and the integration time manually. Effectively disable automatic mode.
- int getIntegrationTime() returns the set integration time in milliseconds
CDR = Current Divisor Ratio
CDR = 1 ==> only 1/8th is measured
TIM = Time Integration Measurement (table)
000 800ms
001 400ms
010 200ms
011 100ms
100 50ms manual only
101 25ms manual only
110 12.5ms manual only
111 6.25ms manual only
Test functions
Function for the conversion math, not meant to be used directly, but by making them public they become testable.
- float convertToLux(uint8_t datahigh, uint8_t datalow) convert intern register format to a LUX value.
Examples
Max44009\examples\max44009_test01
- use for e.g. UNO (use voltage convertor!)
Max44009\examples\max44009_test02
- will not compile for UNO
- use for e.g. ESP32
Notes
Please be aware this is a 3.3 Volt device so it should not be connected to an Arduino UNO or other 5 Volt device directly. Use a level convertor to solve this.
Do not forget to connect the address pin as you cannot read the sensor in a reliable way. As the line will float it will sometimes have the right address and sometimes not. (been there ;)
Future
- improve documentation
- merge MAX44007 library in the future. (shared base class?)
MAX44007
The MAX44007 is an almost identical sensor that uses a step size of 0.025. This implies that this library is not useable 1 to 1 for the MAX44007, however some parts will work/