BH1750 Rojo library

This library will help you programming the sensor BH1750 on the STM32 CUbe IDE that it's a sensor with an I2C driver and some logic inside him.

This software is not an Arduino library

About the sensor

All these data is in the datasheet of the sensor

For more information please check the BH1750FVI datasheet

Features

1. I2C bus Interface ( f / s Mode Support )
2. Spectral responsibility is approximately human eye response
3. Illuminance to Digital Converter
4. Wide range and High resolution. ( 1 - 65535 lx )
5. Low Current by power down function
6. 50Hz / 60Hz Light noise reject-function
7. 1.8V Logic input interface
8. No need any external parts
9. Light source dependency is little. ( ex. Incandescent Lamp. Fluorescent Lamp. Halogen Lamp. White LED. Sun Light )
10. It is possible to select 2 type of I2C slave-address.
11. Adjustable measurement result for influence of optical window ( It is possible to detect min. 0.11 lx, max. 100000 lx by using this function. )
12. Small measurement variation (+/- 20%)
13. The influence of infrared is very small.

Modes table

Measurement mode	Measurement Time	Resolution
H-Resolution Mode2	Typical 120ms	0.5 lx
H-Resolution Mode	Typical 120ms	1 lx
L-Resolution Mode	Typical 16ms	4 lx

Instruction set

Instruction	Opecode	Comments
Power Down	0000_0000	No active state.
Power On	0000_0001	Waiting for measurement command.
Reset	0000_0111	Reset Data register value. Reset command is not acceptable in Power Down mode.
Continuously H-Resolution Mode	0001_0000	Start measurement at 1lx resolution. Measurement Time is typically 120ms.
Continuously H-Resolution Mode2	0001_0001	Start measurement at 0.5lx resolution. Measurement Time is typically 120ms.
Continuously L-Resolution Mode	0001_0011	No active state.
One Time H-Resolution Mode	0010_0000	Start measurement at 1lx resolution. Measurement Time is typically 120ms. It is automatically set to Power Down mode after measurement.
One Time H-Resolution Mode2	0010_0001	Start measurement at 0.5lx resolution. Measurement Time is typically 120ms. It is automatically set to Power Down mode after measurement.
One Time L-Resolution Mode	0010_0011	Start measurement at 4lx resolution. Measurement Time is typically 16ms. It is automatically set to Power Down mode after measurement.
Change Measurement time (High bit)	01000_MT[7,6,5]	Change measurement time. ※ Please refer "adjust measurement result for influence of optical window. (datasheet)"
Change Masurement time(Low bit)	011_MT[4,3,2,1,0]	Change measurement time. ※ Please refer "adjust measurement result for influence of optical window. (datasheet)"
※ Don't input the other opecode.

Native Reduced Measurement Procedure

graph TD;
    A((Power Supply))-->B(PowerDown);
    B(Power Down)--> C(Power On);
    C --> E(One Time Measurement); 
    C{Measurement Command} --> D(Continous Measurement);

Loading

Library Measure Procedure

graph TD;
    A((Initialize))-->B(Read Measurement);

Loading

BH1750 Block Diagram

Block Diagram Descriptions

• PD Photo diode with approximately human eye response.
• AMP Integration-OPAMP for converting from PD current to Voltage.
• ADC AD converter for obtainment Digital 16bit data.
• Logic + I2C Interface Ambient Light Calculation and I2C BUS Interface. It is including below register. Data Register → This is for registration of Ambient Light Data. Initial Value is "0000_0000_0000_0000". Measurement Time Register → This is for registration of measurement time. Initial Value is "0100_0101".
• OSC Internal Oscillator ( typ. 320kHz ). It is CLK for internal logic.

All these information was taken from the BH1750FVI datasheet, for further information go to the datasheet

Sample code of basic use

For STM32F103C8T6

#include "main.h"
#include "Rojo_BH1750.h"
#include <stdio.h>
#include <string.h>
#include <stdint.h>

I2C_HandleTypeDef hi2c1;

void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_I2C1_Init(void);

Rojo_BH1750 BH1750; //Declaration of the sensor structure
float Measure; //Variable that contains the result

int main(void)
{
  HAL_Init();
  SystemClock_Config();
  MX_GPIO_Init();
  MX_I2C1_Init();
  BH1750_Init(&BH1750, &hi2c1, Address_Low); //Initializes with the pin "ADDR" in low
  BH1750_SetResolution(&BH1750, Medium_Res); //Put your value of res
  //Remember use a resolution in "BH1750_Resolutions" enumeration defined in the header file
  while (1)
  {
	  BH1750_Read(&BH1750, &Measure);
	  //By here you are able to read the values of the sensor
	  //It is not necessary to put a delay instruction because the funcion have it
  }
}

Compatible MCU's

• Bluepill Microcontrollers

  • STM32F103C8T6
  • STM32F103C6T6
  • STM32F103C8T6R
  • STM32F103C6T6A

• Blackpill Microcontrollers

  • STM32F401CEU6 - Not tested
  • STM32F411CEU6 - Not tested

Code ready to copy

//Variables
Rojo_BH1750 BH1750; //Declaration of the sensor structure
float Measure; //Variable that will contain the result of the measure

//Main function
BH1750_Init(&BH1750, &hi2c1, Address_Low); //Initializes with the pin "ADDR" in low
BH1750_SetResolution(&BH1750, Medium_Res); //Put your value of res
  
//Infinite loop (while(1))
BH1750_Read(&BH1750, &Measure);

• Remember that the read function have the necessary delays and it's not recommended to put more delays just for this command

By Pedro Rojo

This software is under the terms of Mozilla Public License 2.0

Patch Notes 0.1.0b

Launch release!!

Any bug report, send it to pedroeroca@outlook.com