/* barometer_I2C.c */ // BMP280 Temperature/Pressure sensor. // Relative pressure resolution 0.12 hPa (1m altitude difference). // Temperature resolution 0.01 C (chip temperature). // Arduino UNO R3 // AVR_ATmega328P #define F_CPU 16000000UL #include // register names/addresses and bit names/numbers #include // for the nop instruction #include void _delay_ms ( double ); void _delay_us ( double ); /* UART function prototypes */ void init_uart( void ); unsigned char getchar_uart( void ); void putchar_uart( unsigned char ); void string_out_uart( char * ); // uses strings stored in RAM void Decimal_out_uart( long unsigned int, unsigned char ); // 10 digits 2 decimals /* I2C function prototypes */ void I2C_Init( void ); void I2C_Start( void ); void I2C_Stop( void ); void I2C_Write( unsigned char ); unsigned char I2C_ReadACK( void ); unsigned char I2C_ReadNACK( void ); // BMP280 7-bit device address is 0x77 (with SDO = 1 default by pullup) #define BMP280_WR_ADDRESS 0xEE // 8-bit write address #define BMP280_RD_ADDRESS 0xEF // 8-bit read address // BMP280 alternative 7-bit device address is 0x76 (with SDO = 0, GND) // #define BMP280_WR_ADDRESS 0xEC // 8-bit write address // #define BMP280_RD_ADDRESS 0xED // 8-bit read address void BMP_setup( void ); long signed int I2C_get_raw_temperature( void ); long signed int I2C_get_raw_pressure( void ); long unsigned int calculate_pressure( long signed int ); long signed int calculate_temperature( long signed int ); // individual sensor calibration constants stored in chip BMP280 // Run program "BMP280_calibration_I2C.c" to retrieve constants to paste here const unsigned int dig_T1 = 27391; const signed int dig_T2 = 26007; const signed int dig_T3 = 50; const unsigned int dig_P1 = 38504; const signed int dig_P2 = -10445; const signed int dig_P3 = 3024; const signed int dig_P4 = 7003; const signed int dig_P5 = -131; const signed int dig_P6 = -7; const signed int dig_P7 = 15500; const signed int dig_P8 = -14600; const signed int dig_P9 = 6000; long signed int t_fine; // Global variable "fine resolution temperature value" // value is changed by every temperature recalculation int main(void) { I2C_init(); init_uart( ); BMP_setup(); while(1) { // ctrl_meas 0x25 FORCED mode to make measurements I2C_Start(); I2C_Write( BMP280_WR_ADDRESS ); // BMP280 write address I2C_Write( 0xF4 ); // ctrl_meas register address I2C_Write( 0x25 ); // 0x25 FORCED mode I2C_Stop(); _delay_ms (5000); // check every 5 seconds string_out_uart( "Temperature: " ); Decimal_out_uart( calculate_temperature( I2C_get_raw_temperature() ), 1); // temperature could be negative string_out_uart(" Degrees Celsius\r\n" ); string_out_uart( "Pressure: " ); Decimal_out_uart( calculate_pressure( I2C_get_raw_pressure() ), 0); // absolute pressure is always positive string_out_uart(" millibar (hPa)\r\n" ); } } /* *********************************** */ /* FUNCTIONS */ /* *********************************** */ void I2C_init(void) { //set SCL frequency to < 100kHz the max freq of DS1307 // Bits in TWSR register: "TWS7 TWS6 TWS5 TWS4 TWS3 - TWPS1 TWPS0" TWSR = 0x00; // "xxxxx-00" prescaler set to divide by one // TWBR register: frequency division byte TWBR = 73; // SCLfreq = CPUfreq / (16+2*TWBR*Presc) = 16*10^6 / (16+2*73*1) = 99 kHz //enable TWI // Bits in TWCR register: "TWINT TWEA TWSTA TWSTO TWWC TWEN - TWIE" TWCR = (1 << TWEN); // "-----1--" } // send start signal void I2C_Start( void ) { // Bits in TWCR register: "TWINT TWEA TWSTA TWSTO TWWC TWEN - TWIE" TWCR = (1 << TWINT)|(1 << TWSTA)|(1 << TWEN); // "1-1--1--" while ((TWCR & (1 << TWINT)) == 0); // "?-------" wait for done } // send stop signal void I2C_Stop( void ) { // Bits in TWCR register: "TWINT TWEA TWSTA TWSTO TWWC TWEN - TWIE" TWCR = (1 << TWINT)|(1 << TWSTO)|(1 << TWEN); // "1--1-1--" } void I2C_Write( unsigned char data) { TWDR = data; // Bits in TWCR register: "TWINT TWEA TWSTA TWSTO TWWC TWEN - TWIE" TWCR = (1 << TWINT)|(1 << TWEN); // "1----1--" while ((TWCR & (1 << TWINT)) == 0); // "?-------" wait for done } // read byte with ACK, use for consecutive Bytes read unsigned char I2C_ReadACK(void) { // Bits in TWCR register: "TWINT TWEA TWSTA TWSTO TWWC TWEN - TWIE" // with ACK set TWCR = (1 << TWINT)|(1 << TWEN)|(1 << TWEA); // "11---1--" while ((TWCR & (1 << TWINT)) == 0); // "?-------" wait for done return TWDR; } // read byte with NACK, use with last Byte read unsigned char I2C_ReadNACK( void ) { // Bits in TWCR register: "TWINT TWEA TWSTA TWSTO TWWC TWEN - TWIE" // no acknowledge bit set, NOT ACK TWCR = (1 << TWINT)|(1 << TWEN); // "1----1--" while ((TWCR & (1 << TWINT)) == 0); // "?-------" wait for done return TWDR; } void init_uart( void ) { // Bits in UCSR0B register: "RXCIE0 TXCIE0 UDRIE0 RXEN0 TXEN0 UCSZ02 RXB80 TXB80" UCSR0B |= (1<<(RXEN0)) | (1<<(TXEN0)); // "----1---" // Bits in UCSR0C register: "UMSEL01 UMSEL00 UPM01 UPM00 USBS0 UCSZ01/UCPHA0 UCSZ01/UCPHA0 UCPOL0" UCSR0C |= (1<<(UCSZ01)) | (1<<(UCSZ00)); // "-----11-" UBRR0 = 103; // Baud prescaler 103 -> 9600 Baud } void putchar_uart( unsigned char ch ) { // Bits in UCSR0A register: "RXC0 TXC0 UDRE0 FE0 DOR0 UPE0 U2X0 MPCM0" // wait until the port is ready to be written to while( ( UCSR0A & ( 1<<(UDRE0) ) ) == 0 ){} // write the byte to the serial port UDR0 = ch; } void string_out_uart( char * string ) // use for strings in RAM { while (* string != '\0') putchar_uart(*string ++ ); } void Decimal_out_uart( long unsigned int number, unsigned char signum) { unsigned long int divisor = 1000000000; unsigned char i; unsigned char s[10]; if ( signum == 1 ) // should be treated as signed number { if ((long signed int)number < 0) { number = -number; putchar_uart( '-' );} else putchar_uart( '+' ); } for ( i=0; i<10; i++ ) // populate array with 10 decimal digits { s[i]= (unsigned char)(number/divisor) + '0'; number %= divisor; divisor /= 10; } // find the leading zeros to skip i = 0; while ( (s[i] == '0') && (i < 7) ) i++ ; // print integer part for(i; i<8; i++) putchar_uart(s[i]); // insert decimal point at two decimals putchar_uart('.'); // print fractional part putchar_uart(s[8]); putchar_uart(s[9]); } void BMP_setup( void) { // Weather monitor. Oversampling * 1, SLEEP at setup. // ctrl_meas 0x24 "00100100" SLEEP mode at setup // ctrl_meas 0x25 "00100101" FORCED mode to make measurements // config 0x00 "---000-0" standby time irrelevant in FORCED mode, no Filtering used. /* * * ctrl_meas * "osrs_t2 osrs_t1 osrs_t0 osrs_p2 osrs_p1 osrs_p0 mode1 mode0" * * osrs_t osrs_p mode * 000 NONE 000 NONE 00 SLEEP * 001 * 1 001 * 1 01 FORCED * 010 * 2 010 * 2 (10 FORCED) * 011 * 4 011 * 4 11 NORMAL * 100 * 8 100 * 8 * 101 * 16 101 * 16 * 110 - 110 - * 111 - 111 - * * Config will only be writeable in sleep mode * * config * "t_sb2 tsb_1 tsb0 filter2 filter1 filter0 - spi3w" * * tStandby filter spi3w * 000 0.5 ms 000 OFF 0 OFF (=spi4) * 001 62.5 ms 001 2 1 ON (=spi3) * 010 125 ms 010 4 * 011 250 ms 011 8 * 100 500 ms 100 16 * 101 1 s 101 - * 110 2 s 110 - * 111 4 s 111 - * */ I2C_Start(); I2C_Write( BMP280_WR_ADDRESS ); // BMP280 write address I2C_Write( 0xF4 ); // ctrl_meas register address I2C_Write( 0x24 ); // 0x24 "00100100" SLEEP mode at setup I2C_Stop(); _delay_ms(10); I2C_Start(); I2C_Write( BMP280_WR_ADDRESS ); // BMP280 write address I2C_Write( 0xF5 ); // config register address I2C_Write( 0x00 ); // 0x00 "---000-0" I2C_Stop(); } long signed int I2C_get_raw_temperature( void ) { long signed int adc_T; I2C_Start(); I2C_Write( BMP280_WR_ADDRESS ); // BMP280 write address I2C_Write( 0xFA ); // set address pointer at register temp_msb (0xFA) I2C_Start(); // repeat start I2C_Write( BMP280_RD_ADDRESS ); // BMP280 read address adc_T = ((long unsigned int)I2C_ReadACK()) << 12; // MSB adc_T += ( ( (long unsigned int)I2C_ReadACK() ) << 4 ); // LSB adc_T += ( ( ( (long unsigned int)I2C_ReadNACK() ) << 4 ) & 0x0F ); // XLSB last byte (NACK) I2C_Stop(); return adc_T; } long signed int I2C_get_raw_pressure( void ) { long signed int adc_P; I2C_Start(); I2C_Write( BMP280_WR_ADDRESS ); // BMP280 write address I2C_Write( 0xF7 ); // set address pointer at register press_msb (0xF7) I2C_Start(); // repeat start I2C_Write( BMP280_RD_ADDRESS ); // BMP280 read address adc_P = ((long unsigned int)I2C_ReadACK()) << 12; // MSB adc_P += ( ( (long unsigned int)I2C_ReadACK() ) << 4 ); // LSB adc_P += ( ( ( (long unsigned int)I2C_ReadNACK() ) << 4 ) & 0x0F ); // XLSB last byte (NACK) I2C_Stop(); return adc_P; } long signed int calculate_temperature( long signed int adc_T ) { // Temperature calculation in DegC, resolution is 0.01 DegC. // End Value of T of "5123" equals 51.23 DegC. // t_fine carries "fine temperature" as a global value long signed int var1, var2, T; var1 = ((( (adc_T >>3) - ( (long signed int)dig_T1<<1))) * ( (long signed int)dig_T2) ) >> 11; var2 = (((( (adc_T >>4) -( (long signed int)dig_T1)) * ((adc_T >>4) - ((long signed int)dig_T1))) >> 12) * ((long signed int)dig_T3) ) >> 14; t_fine = var1 + var2; // Global "fine resolution temperature value" is now recalculated T = (t_fine * 5 +128) >> 8; return T; } long unsigned int calculate_pressure( long signed int adc_P ) { // Pressure calculation in Pa as unsigned 32 bit int in Q24.8 format. // (24 integer bits and 8 fractional bits). // End value of p of "24674867" represents 24674867/256=96386.2 Pa = 963.86 hPa long long signed int var1, var2, p; // AVR long long int is 64 bit var1 = ((long long signed int)t_fine) - 128000; // t_fine is global variable var2 = var1 * var1 * (long long signed int)dig_P6; var2 = var2 + ((var1 * (long long signed int)dig_P5) << 17 ); var2 = var2 + (((long long signed int)dig_P4) << 35 ); var1 = ((var1 * var1 * (long long signed int)dig_P3) >> 8) + ((var1 * (long long signed int)dig_P2) << 12); var1 =(((((long long signed int)1)<<47) + var1)) * ((long long signed int)dig_P1) >> 33; p = 1048576 - adc_P; p = (( (p<<31) - var2) * 3125)/var1; var1 = (((long long signed int)dig_P9) *(p>>13) * (p>>13)) >> 25; var2 = (((long long signed int)dig_P8) * p) >> 19; p = ((p + var1 + var2) >> 8) + (((long long signed int)dig_P7 ) <<4); p = ( p + ( ( p & 0x80 ) << 1 ) >> 8 ); // round and divide by 256 return (long unsigned int)p; } /* *********************************** */ /* HARDWARE */ /* *********************************** */ /* Chip ATMega328 Arduino Uno R3 stackable header _______ Digital: _____/ \__ Analog: ______________ ______________ txd ->-|D00 >RXD A5|->-- SCK | \/ | rxd -<-|D01 - SDI Res---|01 PC6/RES' ATM328 SCL/PC5 28|-(A5)->-- SCK -|D02 A3|- txd->-(D00)-|02 PD0/RXD SDA/PC4 27|-(A4)-<>- SDI -|D03~ A2|- rxd-<-(D01)-|03 PD1/TXD PC3 26|-(A3)- -|D04 A1|- -(D02)-|04 PD2/INT0 PC2 25|-(A2)- -|D05~ A0|- -(D03)-|05 PD3/INT1/PWM PC1 24|-(A1)- -|D06~ | Power: -(D04)-|06 PD4 PC0 23|-(A0)- -|D07 Vin|- +5V ---|07 VCC GND 22|--- Gnd | GND|--- GND Gnd ---|08 GND AREF 21|--- Vin -|D08 GND|- Xtal |X|--|09 PB6/OSC1 AVCC 20|--- +5V -|D09~ +5V|--- +5V 16MHz |X|--|10 PB7/OSC2 SCK/PB5 19|-(D13)- -|D10~ +3.3V|- -(D05)-|11 PD5/PWM MISO/PB4 18|-(D12)- -|D11~ Res|- -(D06)-|12 PD6/PWM PWM/MOSI/PB3 17|-(D11)- -|D12 IOREF|- -(D07)-|13 PD7 PWM/SS'/PB2 16|-(D10)- -|D13 LED --- | -(D08)-|14 PB0 PWM/PB1 15|-(D09)- -|GND | |______________________________| -|AREF | -|SCL | -|SDA | |________________| */ /* Bosch Barometer chip Adafruit BMP280 with 5/3 V level translators included __________ | BMP280 | | | +5V ---| 5V | -| 3V3 | GND --| GND | SCL -->-| SCK | -| SDO | SDA -<>-| SDI | -| CSB' | |__________| BMP280 Registers (Byte size): // Control and Status registers 0xD0 : id Chip identification (=0x58) 0xE0 : reset (Write data = 0xB6 to reset) 0xF3 : status "---measuring---updating" 0xF4 : ctrl_meas "osrs_t2 osrs_t1 osrs_t0 osrs_p2 osrs_p1 osrs_p0 mode1 mode0" 0xF5 : config "t_sb2 tsb_1 tsb0 filter2 filter1 filter0 - spi3w" // Temperature and Pressure values from the AD-converter 0xF7 : press_msb 0xF8 : press_lsb 0xF9 : press_xlsb 0xFA : temp_msb 0xFB : temp_lsb 0xFC : temp_xlsb // Indvidual Calibration Constants stored in chip 0x88 : calib00, dig_T1 LSB 0x89 : calib01, dig_T1 MSB 0x8A : calib02, dig_T2 LSB 0x8B : calib03, dig_T2 MSB 0x8C : calib04, dig_T3 LSB 0x8D : calib05, dig_T3 MSB 0x8E : calib06, dig_P1 LSB 0x8F : calib07, dig_P1 MSB 0x90 : calib08, dig_P2 LSB 0x91 : calib09, dig_P2 MSB 0x92 : calib10, dig_P3 LSB 0x93 : calib11, dig_P3 MSB 0x94 : calib12, dig_P4 LSB 0x95 : calib13, dig_P4 MSB 0x96 : calib14, dig_P5 LSB 0x97 : calib15, dig_P5 MSB 0x98 : calib16, dig_P6 LSB 0x99 : calib17, dig_P6 MSB 0x9A : calib18, dig_P7 LSB 0x9B : calib19, dig_P7 MSB 0x9C : calib20, dig_P8 LSB 0x9D : calib21, dig_P8 MSB 0x9E : calib22, dig_P9 LSB 0x9F : calib23, dig_P9 MSB */