BME280 Pressure Readings / Calibration

[michaelas]

I’m reading the values of the BME280 via an MCP3428 4-Channel 4-20mA 16-Bit Converter.
The value for temperature and humidity are no problem, but I get unusual high reading for pressure like 152648.6 .
The standard average atmospheric value is around 1013.25 hPa.

For the code I’m using this library from the official repository:

ncd-io/BME280

Thank you for support in advance.

[michaelas]

Here is the code I’m using, maybe it helps:
(Is there something else, that need to be configured?)

BMyCode.ino (Send data every 10 min)

@michaelas

#include “BME280.h”
#include “MCP3428.h”

#include <application.h>
#include <spark_wiring_i2c.h>

SYSTEM_THREAD(ENABLED);

#define Addr 0x68

int raw_adc1 = 0;
int raw_adc2 = 0;

ApplicationWatchdog wd(60000, System.reset);

#define TEN_MIN_MILLIS (10 * 60 * 1000)
unsigned long lastDateSend = millis() - TEN_MIN_MILLIS;

MCP3428 adc;
BME280 sensor;

void setup()
{
waitUntil(Particle.connected);

adc.init();

sensor.scale = "c";
sensor.init();

Particle.syncTime();

waitFor(Time.isValid, 60000);
lastSync = millis();

Particle.subscribe("hook-response/sendMYData", myHandler, MY_DEVICES);

Wire.begin();

}

void loop()
{

if( (millis() - lastDateSend >= TEN_MIN_MILLIS) )
{
String sTime = Time.format(Time.local(), TIME_FORMAT_ISO8601_FULL) ;
lastDateSend = millis();

  adc.takeReadings();
  sensor.init();
  sensor.loop();
  raw_adc1 = adc.channel_1;
  raw_adc2 = adc.channel_2;
  
  String data = "";
  data = "{";
  data += ",\"1\":" + String(raw_adc2) ; //1 
  data += ",\"2\":" + String(raw_adc1) ; //2 
  data += ",\"3\":" + String(sensor.temperature) ;  
  data += ",\"4\":" + String(sensor.humidity) ;  
  data += ",\"5\":" + String(sensor.pressure) ;  
  data += "}";
      
  bool delivered = Particle.publish("sendMYData", data, PRIVATE, WITH_ACK);
}

}

wd.checkin();
}

[Trey]

Sorry I missed the original post on this, thanks for bringing it to my attention!

I just updated the repo to correct some data types for the compensation variables and that seems to have brought the pressure readings on my desk to where they should be, the only changes are in the .cpp, so nothing in your code needs to change.

Let me know if this solves the inaccuracy on your end.

Thanks!

[michaelas]

I’ve made the update and got following data.
93854.687558879

Local pressure data from the internet:
994 hPa

If the unit is in Pa, then this value is correct!

Thank you very much!
This helped me a lot!