/* BMP280_calculation.c */ // Test program to check pressure and temperature calculations // No sensor is connected. Typical values from BMP280 data sheet are inserted. // 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 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 long signed int get_raw_temperature( void ); long signed int 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 // these are typical values inserted from BMP280 data sheet const unsigned int dig_T1 = 27504; // AVR int is 16 bit const signed int dig_T2 = 26435; const signed int dig_T3 = -1000; const unsigned int dig_P1 = 36477; const signed int dig_P2 = -10685; const signed int dig_P3 = 3024; const signed int dig_P4 = 2855; const signed int dig_P5 = 140; 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 = 128422; // Global variable "fine resolution temperature value" // inserted from BMP280 data sheet int main(void) { init_uart( ); while(1) { string_out_uart( "Temperature: " ); Decimal_out_uart( calculate_temperature( get_raw_temperature() ), 1); // temperature could be negative string_out_uart(" Degrees Celsius\r\n" ); // should print: 25.08 with typical values from BMP280 data sheet string_out_uart("Should print: 25.08\r\n"); string_out_uart( "Pressure: " ); Decimal_out_uart( calculate_pressure( get_raw_pressure() ), 0); // absolute pressure is always positive string_out_uart(" millibar (hPa)\r\n" ); // should print: 1006.53 with typical values from BMP280 data sheet string_out_uart("Should print: 1006.53\r\n"); _delay_ms (5000); // check every 5 seconds } } /* *********************************** */ /* FUNCTIONS */ /* *********************************** */ 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]); } long signed int get_raw_temperature( void ) { // Debug: typical value inserted from BMP280 data sheet long signed int adc_T = 519888; // 20 bit unsigned, in 32 bit signed AD RAW temperature value return adc_T; } long signed int get_raw_pressure( void ) { // Debug: typical value inserted from BMP280 data sheet long signed int adc_P = 415148; // 20 bit unsigned, in 32 bit signed AD RAW pressure value 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/256; // sorry to lose 1 fractional digit return (long unsigned int)p; } /* *********************************** */ /* HARDWARE */ /* *********************************** */ /* Chip ATMega328 Arduino Uno R3 stackable header _______ Digital: _____/ \__ Analog: ______________ ______________ txd ->-|D00 >RXD A5|- | \/ | rxd ->-|D01 -(D00)-|02 PD0/RXD SDA/PC4 27|-(A4)- -|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 ---|08 GND AREF 21|--- Vin -|D08 GND|- Xtal |X|--|09 PB6/OSC1 AVCC 20|--- +5V -|D09~ +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 | SCK ->-| SCK | MISO -<-| SDO | MOSI ->-| SDI | SS' ->-| CSB' | |__________| BMP280 Registers (Byte size): Control and Status registers (R/-) 0xD0/- : id Chip identification (=0x58) (-/W) -/0x60 : reset (Write data = 0xB6 to reset) (R/-) 0xF3/- : status "---measuring---updating" (R/W) 0xF4/0x74 : ctrl_meas "osrs_t2 osrs_t1 osrs_t0 osrs_p2 osrs_p1 osrs_p0 mode1 mode0" (R/W) 0xF5/0x75 : config "t_sb2 tsb_1 tsb0 filter2 filter1 filter0 - spi3w" Temperature and Pressure values from the AD-converter (R/-) 0xF7/- : press_msb (R/-) 0xF8/- : press_lsb (R/-) 0xF9/- : press_xlsb (R/-) 0xFA/- : temp_msb (R/-) 0xFB/- : temp_lsb (R/-) 0xFC/- : temp_xlsb Indvidual Calibration Constants stored in chip (R/-) 0x88/- : calib00, dig_T1 LSB (R/-) 0x89/- : calib01, dig_T1 MSB (R/-) 0x8A/- : calib02, dig_T2 LSB (R/-) 0x8B/- : calib03, dig_T2 MSB (R/-) 0x8C/- : calib04, dig_T3 LSB (R/-) 0x8D/- : calib05, dig_T3 MSB (R/-) 0x8E/- : calib06, dig_P1 LSB (R/-) 0x8F/- : calib07, dig_P1 MSB (R/-) 0x90/- : calib08, dig_P2 LSB (R/-) 0x91/- : calib09, dig_P2 MSB (R/-) 0x92/- : calib10, dig_P3 LSB (R/-) 0x93/- : calib11, dig_P3 MSB (R/-) 0x94/- : calib12, dig_P4 LSB (R/-) 0x95/- : calib13, dig_P4 MSB (R/-) 0x96/- : calib14, dig_P5 LSB (R/-) 0x97/- : calib15, dig_P5 MSB (R/-) 0x98/- : calib16, dig_P6 LSB (R/-) 0x99/- : calib17, dig_P6 MSB (R/-) 0x9A/- : calib18, dig_P7 LSB (R/-) 0x9B/- : calib19, dig_P7 MSB (R/-) 0x9C/- : calib20, dig_P8 LSB (R/-) 0x9D/- : calib21, dig_P8 MSB (R/-) 0x9E/- : calib22, dig_P9 LSB (R/-) 0x9F/- : calib23, dig_P9 MSB */