M5Paper and BME280 Sensor

Powersoft

Because the BME280 library didn't want to work with the M5Paper Wire1 I2c connection, I changed the routines so that they now work.

The adjustment now works for M5Stack, the M5Paper and for the Core2.
I post the complete code here, because I cannot upload a zip file.
he whole consists of:

M5Paper_BME280.uno
BME280.h
BME280_routines

1. M5Paper_BME280.uno

/*
 * BME280 Sensor (Temperature,Pressure, and Humidity) 
 * Is working now also for M5Paper, and testest on all M5Stack devices
 * Rewritten by J.Kromhout (NL)
 * Version 1.0
 * Date : 24-02-2021
 * 
 * Todo:  Beter input for smapling etc.
 *        Making the routine universal for BME280 and BMP280
 */

#include <M5EPD.h>
#include <Wire.h>

#include "BME280.h" /* definition file */

double p,t,h; /* pressure,temperature and humidity */

void setup() {
  M5.begin();
  Wire1.begin(25,32); /* start Wire1 on M5Paper */
  getBME280(&Wire1, &t, &p, &h); /* get messurment*/
  Serial.println("-------------------------");
  Serial.printf("Temperature : %6.1f °C\n",   t);
  Serial.printf("Barometer   : %6.1f hPa\n",  p);
  Serial.printf("Humidity    : %6.1f %%\n",   h);
  Serial.println("-------------------------");
}

void loop() {
  // put your main code here, to run repeatedly:

}


void getBME280(TwoWire *theWire, double *t, double *p, double *h)
{
  _i2c = theWire;

  /* check of BME280 is avilable */
  uint8_t value = read8(0xD0);  
  if (value == 0x60)
    Serial.println("BME280 found");
  else
  {
    Serial.println("No BME280 found! Check your device........");
    while(true);
  }
  reset_BME280();                                     // Reset BME280      
  write8(BME280_REGISTER_CONTROLHUMID,(uint8_t)0x01); // Select control humidity register
  write8(BME280_REGISTER_CONTROL,     (uint8_t)0x27); // Select control measurement register
  write8(BME280_REGISTER_CONFIG,      (uint8_t)0xA0); // Select config register
  readCoefficients();                                 // Read coefficients from BME280
  *t = get_Temperature();                             // Get temperature
  *p = get_Pressure()/100.0;                          // Get pressure
  *h = get_Humidity();                                // Get Humidity
}

2. BME280.h

#define BME280_ADDRESS 0x77  /* Primary I2C Address */
TwoWire *_i2c;
uint8_t _i2caddr = BME280_ADDRESS;


int32_t t_fine; /* tempory variable */

/* calibration data, need for calculation */
uint16_t  dig_T1; 
int16_t   dig_T2;  
int16_t   dig_T3;  

uint16_t  dig_P1; 
int16_t   dig_P2;  
int16_t   dig_P3;  
int16_t   dig_P4;  
int16_t   dig_P5;  
int16_t   dig_P6;  
int16_t   dig_P7;  
int16_t   dig_P8; 
int16_t   dig_P9;  

uint8_t   dig_H1; 
int16_t   dig_H2; 
uint8_t   dig_H3; 
int16_t   dig_H4; 
int16_t   dig_H5; 
int8_t    dig_H6;  

/* Calibrate registers addresses */
#define BME280_REGISTER_DIG_T1        0x88
#define BME280_REGISTER_DIG_T2        0x8A
#define BME280_REGISTER_DIG_T3        0x8C
#define BME280_REGISTER_DIG_P1        0x8E
#define BME280_REGISTER_DIG_P2        0x90
#define BME280_REGISTER_DIG_P3        0x92
#define BME280_REGISTER_DIG_P4        0x94
#define BME280_REGISTER_DIG_P5        0x96
#define BME280_REGISTER_DIG_P6        0x98
#define BME280_REGISTER_DIG_P7        0x9A
#define BME280_REGISTER_DIG_P8        0x9C
#define BME280_REGISTER_DIG_P9        0x9E
#define BME280_REGISTER_DIG_H1        0xA1
#define BME280_REGISTER_DIG_H2        0xE1
#define BME280_REGISTER_DIG_H3        0xE3
#define BME280_REGISTER_DIG_H4        0xE4
#define BME280_REGISTER_DIG_H5        0xE5
#define BME280_REGISTER_DIG_H6        0xE7
/* ontrol registers */
#define BME280_REGISTER_CHIPID        0xD0
#define BME280_REGISTER_VERSION       0xD1
#define BME280_REGISTER_SOFTRESET     0xE0
#define BME280_REGISTER_CAL26         0xE1 
#define BME280_REGISTER_CONTROLHUMID  0xF2
#define BME280_REGISTER_STATUS        0xF3
#define BME280_REGISTER_CONTROL       0xF4
#define BME280_REGISTER_CONFIG        0xF5
#define BME280_REGISTER_PRESSUREDATA  0xF7
#define BME280_REGISTER_TEMPDATA      0xFA
#define BME280_REGISTER_HUMIDDATA     0xFD

3. BME280_routines

uint8_t read8(byte reg) 
{
  uint8_t value;
  _i2c->beginTransmission((uint8_t)BME280_ADDRESS);
  _i2c->write((uint8_t)reg);
  _i2c->endTransmission();
  _i2c->requestFrom((uint8_t)BME280_ADDRESS,(uint8_t)1);
  value = _i2c->read();
  return value;
}
    
void write8(byte reg , byte value) 
{
  _i2c->beginTransmission((uint8_t)BME280_ADDRESS);
  _i2c->write((uint8_t)reg);
  _i2c->write((uint8_t)value);
  _i2c->endTransmission();
}

uint16_t read16(byte reg) 
{
  uint16_t value;
  _i2c->beginTransmission((uint8_t) BME280_ADDRESS);
  _i2c->write((uint8_t)reg);
  _i2c->endTransmission();
  _i2c->requestFrom((uint8_t)BME280_ADDRESS,(uint8_t)2);
  value = (_i2c->read() << 8) | _i2c->read();
  return value;
}

uint32_t read24(byte reg) 
{
  uint32_t value;
    _i2c->beginTransmission((uint8_t)BME280_ADDRESS);
    _i2c->write((uint8_t)reg);
    _i2c->endTransmission();
    _i2c->requestFrom((uint8_t)BME280_ADDRESS,(uint8_t)3);

    value = _i2c->read();
    value <<= 8;
    value |= _i2c->read();
    value <<= 8;
    value |= _i2c->read();
    return value;
}

uint16_t read16_LE(byte reg) 
{
  uint16_t temp = read16(reg);
  return (temp >> 8) | (temp << 8);
}

int16_t readS16(byte reg) 
{ 
  return (int16_t) read16(reg); 
}

int16_t readS16_LE(byte reg) 
{
  return (int16_t) read16_LE(reg);
}

void readCoefficients() 
{
  dig_T1  = read16_LE(BME280_REGISTER_DIG_T1);
  dig_T2  = readS16_LE(BME280_REGISTER_DIG_T2);
  dig_T3  = readS16_LE(BME280_REGISTER_DIG_T3);

  dig_P1  = read16_LE(BME280_REGISTER_DIG_P1);
  dig_P2  = readS16_LE(BME280_REGISTER_DIG_P2);
  dig_P3  = readS16_LE(BME280_REGISTER_DIG_P3);
  dig_P4  = readS16_LE(BME280_REGISTER_DIG_P4);
  dig_P5  = readS16_LE(BME280_REGISTER_DIG_P5);
  dig_P6  = readS16_LE(BME280_REGISTER_DIG_P6);
  dig_P7  = readS16_LE(BME280_REGISTER_DIG_P7);
  dig_P8  = readS16_LE(BME280_REGISTER_DIG_P8);
  dig_P9  = readS16_LE(BME280_REGISTER_DIG_P9);

  dig_H1 = read8(BME280_REGISTER_DIG_H1);
  dig_H2 = readS16_LE(BME280_REGISTER_DIG_H2);
  dig_H3 = read8(BME280_REGISTER_DIG_H3);
  dig_H4 = ((int8_t)read8(BME280_REGISTER_DIG_H4) << 4) | (read8(BME280_REGISTER_DIG_H4 + 1) & 0xF);
  dig_H5 = ((int8_t)read8(BME280_REGISTER_DIG_H5 + 1) << 4) | (read8(BME280_REGISTER_DIG_H5) >> 4);
  dig_H6 = (int8_t)read8(BME280_REGISTER_DIG_H6);
}

double get_Temperature() {
  int32_t var1, var2;
  int32_t adc_T = read24(BME280_REGISTER_TEMPDATA);
  adc_T >>= 4;

  var1 = ((((adc_T >> 3) - ((int32_t)dig_T1 << 1))) *
          ((int32_t)dig_T2)) >> 11;

  var2 = (((((adc_T >> 4) - ((int32_t)dig_T1)) *
            ((adc_T >> 4) - ((int32_t)dig_T1))) >> 12) *
          ((int32_t)dig_T3)) >> 14;

  t_fine = var1 + var2;

  double T = (t_fine * 5 + 128) >> 8;
  return T / 100;
}

double get_Pressure() {
  int64_t var1, var2, p;
  // Must be done first to get the t_fine variable set up
  get_Temperature();

  int32_t adc_P = read24(BME280_REGISTER_PRESSUREDATA);
  adc_P >>= 4;

  var1 = ((int64_t)t_fine) - 128000;
  var2 = var1 * var1 * (int64_t)dig_P6;
  var2 = var2 + ((var1 * (int64_t)dig_P5) << 17);
  var2 = var2 + (((int64_t)dig_P4) << 35);
  var1 = ((var1 * var1 * (int64_t)dig_P3) >> 8) +
         ((var1 * (int64_t)dig_P2) << 12);
  var1 = (((((int64_t)1) << 47) + var1)) * ((int64_t)dig_P1) >> 33;

  if (var1 == 0) {
    return 0; // avoid exception caused by division by zero
  }
  p = 1048576 - adc_P;
  p = (((p << 31) - var2) * 3125) / var1;
  var1 = (((int64_t)dig_P9) * (p >> 13) * (p >> 13)) >> 25;
  var2 = (((int64_t)dig_P8) * p) >> 19;

  p = ((p + var1 + var2) >> 8) + (((int64_t)dig_P7) << 4);
  return (double)p / 256;
}

double get_Humidity(void) {
  get_Temperature(); // must be done first to get t_fine

  int32_t adc_H = read16(BME280_REGISTER_HUMIDDATA);
  if (adc_H == 0x8000) // value in case humidity measurement was disabled
    return NAN;

  int32_t v_x1_u32r;

  v_x1_u32r = (t_fine - ((int32_t)76800));

  v_x1_u32r = (((((adc_H << 14) - (((int32_t)dig_H4) << 20) -
                  (((int32_t)dig_H5) * v_x1_u32r)) +
                 ((int32_t)16384)) >>
                15) * (((((((v_x1_u32r * ((int32_t)dig_H6)) >> 10) *
                    (((v_x1_u32r * ((int32_t)dig_H3)) >> 11) + ((int32_t)32768))) >>
                   10) + ((int32_t)2097152)) * ((int32_t)dig_H2) + 8192) >> 14));

  v_x1_u32r = (v_x1_u32r - (((((v_x1_u32r >> 15) * (v_x1_u32r >> 15)) >> 7) * ((int32_t)dig_H1)) >> 4));
  v_x1_u32r = (v_x1_u32r < 0) ? 0 : v_x1_u32r;
  v_x1_u32r = (v_x1_u32r > 419430400) ? 419430400 : v_x1_u32r;
  double h = (v_x1_u32r >> 12);
  return h / 1024.0;
}


void reset_BME280()
{
  write8(BME280_REGISTER_SOFTRESET , (uint8_t)0xB6);
}

Have fun with it. Let us know when there are improvements.
Cheers,

Jan

Powersoft

Make an improvement in the main call routine. The return value of getBME280 is a boolean.
now it is possible to check whether a BME280 is connected correctly.

bool getBME280(TwoWire *theWire, double *t, double *p, double *h)
{
  _i2c = theWire;

  /* check of BME280 is avilable */
  uint8_t value = read8(0xD0);  
  if (value == 0x60)                                    // BME280 detected
  {
    reset_BME280();                                     // Reset BME280      
    write8(BME280_REGISTER_CONTROLHUMID,(uint8_t)0x01); // Select control humidity register
    write8(BME280_REGISTER_CONTROL,     (uint8_t)0x27); // Select control measurement register
    write8(BME280_REGISTER_CONFIG,      (uint8_t)0xA0); // Select config register
    readCoefficients();                                 // Read coefficients from BME280
    *t = get_Temperature();                             // Get temperature
    *p = get_Pressure()/100.0;                          // Get pressure
    *h = get_Humidity();                                // Get Humidity
    return true;
  }
  else
  {
    return false;                                       // No BME280 detected
  }
}

Cheers,

Jan