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BH1750.c
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BH1750.c
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/* ************************************************************************
*
* functions for BH1750FVI (ambient light sensor, I2C bus)
*
* (c) 2024 by Markus Reschke
*
* ************************************************************************ */
/*
* hints:
* - pin assignment
* SCL I2C: SCL
* SDA I2C: SDA
* ADDR Gnd or Vcc
* - I2C clock modes: standard (100kHz) and fast (400kHz)
* - Vcc 3.3V
* I2C pull-up resistors to 3.3V should be ok for a 5V ATmega
*/
/* local includes */
#include "config.h" /* global configuration */
#ifdef HW_BH1750
/*
* local constants
*/
/* source management */
#define BH1750_C
/* operation modes */
#define MODE_MANUAL 0 /* manual mode */
#define MODE_AUTO 1 /* automatic mode */
/* I2C addreses */
#define BH1750_I2C_ADDR_0 0b00100011 /* ADDR=0 0x23 */
#define BH1750_I2C_ADDR_1 0b01011100 /* ADDR=1 0x5c */
/*
* instruction set
*/
/* power down */
#define BH1750_POWER_DOWN 0b00000000
/* power on (and wait for measurement command) */
#define BH1750_POWER_UP 0b00000001
/* reset data register (not in power down mode) */
#define BH1750_RESET 0b00000111
/* run measurement in continuous high resolution mode 1 (1 lx) */
#define BH1750_CONT_HIRES_1 0b00010000
/* run measurement in continuous high resolution mode 2 (0.5 lx) */
#define BH1750_CONT_HIRES_2 0b00010001
/* run measurement in continuous low resolution mode (4 lx) */
#define BH1750_CONT_LOWRES 0b00010011
/* run measurement in one-time high resolution mode 1 (1 lx) */
#define BH1750_SINGLE_HIRES_1 0b00100000
/* run measurement in one-time high resolution mode 2 (0.5 lx) */
#define BH1750_SINGLE_HIRES_2 0b00100001
/* run measurement in one-time low resolution mode (4 lx) */
#define BH1750_SINGLE_LOWRES 0b00100011
/* change measurement time, high bits (bits 7-5) */
#define BH1750_TIME_HIGH 0b01000000
/* change measurement time, low bits (bits 4-0) */
#define BH1750_TIME_LOW 0b01100000
/*
* include header files
*/
/* local includes */
#include "common.h" /* common header file */
#include "variables.h" /* global variables */
#include "functions.h" /* external functions */
/* ************************************************************************
* low level functions for I2C interface
* ************************************************************************ */
/*
* send command to BH1750
*
* requires:
* - Command
*
* returns:
* - 1 on success
* - 0 on any problem
*/
uint8_t BH1750_SendCommand(uint8_t Command)
{
uint8_t Flag = 0; /* return value */
uint8_t OldTimeout; /* old ACK timeout */
OldTimeout = I2C.Timeout; /* save old timeout */
if (I2C_Start(I2C_START) == I2C_OK) /* start */
{
I2C.Byte = BH1750_I2C_ADDR << 1; /* address (7 bits) & write (0) */
I2C.Timeout = 1; /* ACK timeout 10µs */
/* send address & write bit, expect ACK from BH1750 */
if (I2C_WriteByte(I2C_ADDRESS) == I2C_ACK) /* address BH1750 */
{
I2C.Byte = Command; /* set command */
/* send command, expect ACK from BH1750 */
if (I2C_WriteByte(I2C_DATA) == I2C_ACK) /* send data */
{
Flag = 1; /* signal success */
}
}
}
I2C_Stop(); /* stop */
I2C.Timeout = OldTimeout; /* restore old timeout */
return Flag;
}
/*
* read light intensity value from BH1750
*
* requires:
* - Value: pointer to raw value
*
* returns:
* - 1 on success
* - 0 on any problem
*/
uint8_t BH1750_ReadValue(uint16_t *Value)
{
uint8_t Flag = 0; /* return value */
uint8_t HighByte; /* high byte */
uint16_t RawValue; /* raw value */
uint8_t OldTimeout; /* old ACK timeout */
OldTimeout = I2C.Timeout; /* save old timeout */
if (I2C_Start(I2C_START) == I2C_OK) /* start */
{
/* address (7 bits) & read (1) */
I2C.Byte = (BH1750_I2C_ADDR << 1) | 0b00000001;
I2C.Timeout = 1; /* ACK timeout 10µs */
/* send address & read bit, expect ACK from BH1750 */
if (I2C_WriteByte(I2C_ADDRESS) == I2C_ACK) /* address BH1750 */
{
/* read high byte and ACK */
if (I2C_ReadByte(I2C_ACK) == I2C_OK) /* read first byte */
{
HighByte = I2C.Byte; /* save byte */
/* read low byte and NACK */
if (I2C_ReadByte(I2C_NACK) == I2C_OK) /* read second byte */
{
/* pre-process data */
RawValue = HighByte; /* copy high byte */
RawValue <<= 8; /* and shift to MSB */
RawValue |= I2C.Byte; /* copy low byte */
*Value = RawValue; /* save result */
Flag = 1; /* signal success */
}
}
}
}
I2C_Stop(); /* stop */
I2C.Timeout = OldTimeout; /* restore old timeout */
return Flag;
}
/* ************************************************************************
* high level functions
* ************************************************************************ */
/*
* measurement modes and times:
* - resolution mode resolution typ. time max. time
* high resolution 1 1 lx 120 ms 180 ms
* high resolution 2 0.5 lx 120 ms 180 ms
* low resolution 4 lx 16 ms 24 ms
* - modes
* continuously: stay in power on mode
* one-time: automaticly power down after measurement
*/
/*
* BH1750: read light intensity
*
* requires:
* - Value: pointer to light intensity in Lux
* - Scale: pointer to scale factor / decimal places
*
* returns:
* - 1 on success
* - 0 on any problem
*/
uint8_t BH1750_ReadLux(uint32_t *Value, uint8_t *Scale)
{
uint8_t Flag = 0; /* return value */
uint16_t RawValue; /* raw value */
uint32_t Temp; /* temporary value */
/*
* measure light intensity
*/
/* send command: measure in continuous high resolution mode 1 */
if (BH1750_SendCommand(BH1750_CONT_HIRES_1) == 1) /* done */
{
/* conversion time 120-180ms */
MilliSleep(180); /* wait 180ms */
/* read raw value */
if (BH1750_ReadValue(&RawValue) == 1) /* done */
{
Flag = 1; /* signal success */
}
}
/*
* convert raw value to Lux
*/
Temp = RawValue; /* copy raw value */
Temp *= 100; /* scale to 10^-2 */
/* apply accuracy factor (/1.2) */
Temp /= 12; /* /12 (scaled to 10^-1) */
*Value = Temp; /* save Lux value */
*Scale = 1; /* 1 decimal place (10^-1) */
return Flag;
}
/* ************************************************************************
* tool
* ************************************************************************ */
/*
* BH1750 tool
* - reads and displays light intensity (in Lux)
*/
void BH1750_Tool(void)
{
uint8_t Flag = 1; /* loop control */
uint8_t Test; /* key / feedback */
uint8_t Mode = MODE_MANUAL; /* operation mode */
uint16_t Timeout = 0; /* timeout for user feedback */
uint8_t Scale; /* Lux scale / decimal places */
uint32_t Value; /* Lux value */
/*
* display info
*/
LCD_Clear();
#ifdef UI_COLORED_TITLES
Display_ColoredEEString(BH1750_str, COLOR_TITLE); /* display: BH1750 */
#else
Display_EEString(BH1750_str); /* display: BH1750 */
#endif
LCD_CharPos(1, 2); /* move to line #2 */
Display_EEString(Start_str); /* display: Start */
/*
* power on BH1750
* - BH1750 enters power down mode after Vcc is applied
*/
/* send command: power up */
if (BH1750_SendCommand(BH1750_POWER_UP) == 0) /* can't power on */
{
/* inform user */
LCD_ClearLine2(); /* clear line #2 */
Display_EEString(Error_str); /* display: Error */
WaitKey(); /* wait for user feedback */
Flag = 0; /* don't proceed */
}
/*
* processing loop
*/
while (Flag)
{
/*
* user input
*/
/* wait for user input */
Test = TestKey(Timeout, CURSOR_BLINK | CHECK_KEY_TWICE | CHECK_BAT);
if (Test == KEY_LONG) /* long key press */
{
/* display mode in line #1 */
LCD_ClearLine(1); /* clear line #1 */
LCD_CharPos(1, 1); /* move to line #1 */
#ifdef UI_COLORED_TITLES
Display_ColoredEEString_Space(BH1750_str, COLOR_TITLE);
#else
Display_EEString_Space(BH1750_str);
#endif
/* change mode */
if (Mode == MODE_MANUAL) /* manual mode */
{
Mode = MODE_AUTO; /* set automatic mode */
Timeout = 1000; /* wait for max. 1s */
/* indicate auto mode */
Display_Char('*'); /* display: * */
}
else /* automatic mode */
{
Mode = MODE_MANUAL; /* set manual mode again */
Timeout = 0; /* wait for user */
}
MilliSleep(500); /* smooth UI */
}
else if (Test == KEY_TWICE) /* two short key presses */
{
Flag = 0; /* end loop */
}
LCD_ClearLine2(); /* clear line #2 */
/*
* read and show light intensity
*/
if (Flag) /* ok to proceed */
{
/* get light intensity from BH1750 (in Lux) */
Test = BH1750_ReadLux(&Value, &Scale);
if (Test) /* got value */
{
/* display Lux value */
Display_FullValue(Value, Scale, 'l');
Display_Char('x');
}
else /* some error */
{
Display_Minus(); /* display: - */
}
}
}
/*
* power down BH1750
* - ignore any errors
*/
BH1750_SendCommand(BH1750_POWER_DOWN); /* send command: power down */
}
/* ************************************************************************
* clean-up of local constants
* ************************************************************************ */
/* local constants */
#undef MODE_MANUAL
#undef MODE_AUTO
#undef BH1750_I2C_ADDR_0
#undef BH1750_I2C_ADDR_1
/* source management */
#undef BH1750_C
#endif
/* ************************************************************************
* EOF
* ************************************************************************ */