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# 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.


## Schema breakout max44009 / GY-49


```cpp
//  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(address, dataPin, clockPin)** Constructor with dataPin (sda) and clockPin (scl) for ESP32 and ESP8266
- **Max44009(address, begin = Boolean::True)** Constructor for other boards e.g. UNO.
- **Max44009(begin = Boolean::True)** Constructor with default I2C address 0x4A == 74.
- **void configure(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.

```cpp
// 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)** 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(void)** returns the value set.
- **bool setLowThreshold(float)** 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(void)** returns the value set.
- **void setThresholdTimer(uint8_t)** 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 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 ;)