💬 Atmospheric Pressure Sensor

ghislain

i've got a problem, pressure always stay to 1013 mbar and i'm at 350m of altitude. Something is wrong but what ? I test the BMP180 alone and it said the good value.

ghislain

I found some problems in code. I did make some change to be able to get value. I replace "float pressure = bmp.readSealevelPressure(ALTITUDE) / 100.0;" by "float pressure = bmp.readPressure() / 100 ;"

I'll make a PR on GitHub when everything will be well tested. :)

James Flosse

Hi, i've a problem with the bmp180 with domoticz. I use raspberry pi with domoticz and mysensor v2 and nrf24 on gpio, i receive data but i think is wrong. The temperature is 31°C and pressure is 728. I put my altitude in the sketch.
Can you help me?
Best regards.

mfalkvidd

Welcome to the MySensors community @James-Flosse !

Could you post your sketch and debug output from the node and the gateway?

If you haven't looked at it already, https://www.mysensors.org/build/debug#enabling-debug-logging has information on how to enable debug logging.

James Flosse

Hi @mfalkvidd. This is the debug output and my code

2269 MCO:REG:REQ
2277 TSF:MSG:SEND,3-3-0-0,s=255,c=3,t=26,pt=1,l=1,sg=0,ft=0,st=OK:2
2287 TSF:MSG:READ,0-0-3,s=255,c=3,t=27,pt=1,l=1,sg=0:1
2293 MCO:PIM:NODE REG=1
2295 MCO:BGN:STP
2306 MCO:BGN:INIT OK,TSP=1
Forecast at minute 1 dP/dt = 0.00kPa/h --> unknown
Temperature = 31.00 *C
Pressure = 728.00 hPa
Forecast = unknown
2359 TSF:MSG:SEND,3-3-0-0,s=1,c=1,t=0,pt=7,l=5,sg=0,ft=0,st=OK:31.0
2369 TSF:MSG:SEND,3-3-0-0,s=0,c=1,t=4,pt=7,l=5,sg=0,ft=0,st=OK:728
2381 TSF:MSG:SEND,3-3-0-0,s=0,c=1,t=5,pt=0,l=7,sg=0,ft=0,st=OK:unknown
2387 MCO:SLP:MS=60000,SMS=0,I1=255,M1=255,I2=255,M2=255
2394 MCO:SLP:TPD

// Enable debug prints to serial monitor
#define MY_DEBUG 

// Enable and select radio type attached
#define MY_RADIO_NRF24
//#define MY_RADIO_RFM69

#include <SPI.h>
#include <MySensors.h>  
#include <Wire.h>
#include <Adafruit_BMP085.h>

#define BARO_CHILD 0
#define TEMP_CHILD 1

const float ALTITUDE = 688; // <-- adapt this value to your own location's altitude.

// Sleep time between reads (in seconds). Do not change this value as the forecast algorithm needs a sample every minute.
const unsigned long SLEEP_TIME = 60000; 

const char *weather[] = { "stable", "sunny", "cloudy", "unstable", "thunderstorm", "unknown" };
enum FORECAST
{
    STABLE = 0,            // "Stable Weather Pattern"
    SUNNY = 1,            // "Slowly rising Good Weather", "Clear/Sunny "
    CLOUDY = 2,            // "Slowly falling L-Pressure ", "Cloudy/Rain "
    UNSTABLE = 3,        // "Quickly rising H-Press",     "Not Stable"
    THUNDERSTORM = 4,    // "Quickly falling L-Press",    "Thunderstorm"
    UNKNOWN = 5            // "Unknown (More Time needed)
};

Adafruit_BMP085 bmp = Adafruit_BMP085();      // Digital Pressure Sensor 

float lastPressure = -1;
float lastTemp = -1;
int lastForecast = -1;

const int LAST_SAMPLES_COUNT = 5;
float lastPressureSamples[LAST_SAMPLES_COUNT];

// this CONVERSION_FACTOR is used to convert from Pa to kPa in forecast algorithm
// get kPa/h be dividing hPa by 10 
#define CONVERSION_FACTOR (1.0/10.0)

int minuteCount = 0;
bool firstRound = true;
// average value is used in forecast algorithm.
float pressureAvg;
// average after 2 hours is used as reference value for the next iteration.
float pressureAvg2;

float dP_dt;
bool metric;
MyMessage tempMsg(TEMP_CHILD, V_TEMP);
MyMessage pressureMsg(BARO_CHILD, V_PRESSURE);
MyMessage forecastMsg(BARO_CHILD, V_FORECAST);


void setup() 
{
    if (!bmp.begin()) 
    {
        Serial.println("Could not find a valid BMP085 sensor, check wiring!");
        while (1) {}
    }
    metric = getControllerConfig().isMetric;
}

void presentation()  {
  // Send the sketch version information to the gateway and Controller
  sendSketchInfo("Pressure Sensor", "1.1");

  // Register sensors to gw (they will be created as child devices)
  present(BARO_CHILD, S_BARO);
  present(TEMP_CHILD, S_TEMP);
}

void loop() 
{
    float pressure = bmp.readPressure() / 100 ;
    float temperature = bmp.readTemperature();

    if (!metric) 
    {
        // Convert to fahrenheit
        temperature = temperature * 9.0 / 5.0 + 32.0;
    }

    int forecast = sample(pressure);

    Serial.print("Temperature = ");
    Serial.print(temperature);
    Serial.println(metric ? " *C" : " *F");
    Serial.print("Pressure = ");
    Serial.print(pressure);
    Serial.println(" hPa");
    Serial.print("Forecast = ");
    Serial.println(weather[forecast]);


    if (temperature != lastTemp) 
    {
        send(tempMsg.set(temperature, 1));
        lastTemp = temperature;
    }

    if (pressure != lastPressure) 
    {
        send(pressureMsg.set(pressure, 0));
        lastPressure = pressure;
    }

    if (forecast != lastForecast)
    {
        send(forecastMsg.set(weather[forecast]));
        lastForecast = forecast;
    }

    sleep(SLEEP_TIME);
}

float getLastPressureSamplesAverage()
{
    float lastPressureSamplesAverage = 0;
    for (int i = 0; i < LAST_SAMPLES_COUNT; i++)
    {
        lastPressureSamplesAverage += lastPressureSamples[i];
    }
    lastPressureSamplesAverage /= LAST_SAMPLES_COUNT;

    return lastPressureSamplesAverage;
}



// Algorithm found here
// http://www.freescale.com/files/sensors/doc/app_note/AN3914.pdf
// Pressure in hPa -->  forecast done by calculating kPa/h
int sample(float pressure)
{
    // Calculate the average of the last n minutes.
    int index = minuteCount % LAST_SAMPLES_COUNT;
    lastPressureSamples[index] = pressure;

    minuteCount++;
    if (minuteCount > 185)
    {
        minuteCount = 6;
    }

    if (minuteCount == 5)
    {
        pressureAvg = getLastPressureSamplesAverage();
    }
    else if (minuteCount == 35)
    {
        float lastPressureAvg = getLastPressureSamplesAverage();
        float change = (lastPressureAvg - pressureAvg) * CONVERSION_FACTOR;
        if (firstRound) // first time initial 3 hour
        {
            dP_dt = change * 2; // note this is for t = 0.5hour
        }
        else
        {
            dP_dt = change / 1.5; // divide by 1.5 as this is the difference in time from 0 value.
        }
    }
    else if (minuteCount == 65)
    {
        float lastPressureAvg = getLastPressureSamplesAverage();
        float change = (lastPressureAvg - pressureAvg) * CONVERSION_FACTOR;
        if (firstRound) //first time initial 3 hour
        {
            dP_dt = change; //note this is for t = 1 hour
        }
        else
        {
            dP_dt = change / 2; //divide by 2 as this is the difference in time from 0 value
        }
    }
    else if (minuteCount == 95)
    {
        float lastPressureAvg = getLastPressureSamplesAverage();
        float change = (lastPressureAvg - pressureAvg) * CONVERSION_FACTOR;
        if (firstRound) // first time initial 3 hour
        {
            dP_dt = change / 1.5; // note this is for t = 1.5 hour
        }
        else
        {
            dP_dt = change / 2.5; // divide by 2.5 as this is the difference in time from 0 value
        }
    }
    else if (minuteCount == 125)
    {
        float lastPressureAvg = getLastPressureSamplesAverage();
        pressureAvg2 = lastPressureAvg; // store for later use.
        float change = (lastPressureAvg - pressureAvg) * CONVERSION_FACTOR;
        if (firstRound) // first time initial 3 hour
        {
            dP_dt = change / 2; // note this is for t = 2 hour
        }
        else
        {
            dP_dt = change / 3; // divide by 3 as this is the difference in time from 0 value
        }
    }
    else if (minuteCount == 155)
    {
        float lastPressureAvg = getLastPressureSamplesAverage();
        float change = (lastPressureAvg - pressureAvg) * CONVERSION_FACTOR;
        if (firstRound) // first time initial 3 hour
        {
            dP_dt = change / 2.5; // note this is for t = 2.5 hour
        }
        else
        {
            dP_dt = change / 3.5; // divide by 3.5 as this is the difference in time from 0 value
        }
    }
    else if (minuteCount == 185)
    {
        float lastPressureAvg = getLastPressureSamplesAverage();
        float change = (lastPressureAvg - pressureAvg) * CONVERSION_FACTOR;
        if (firstRound) // first time initial 3 hour
        {
            dP_dt = change / 3; // note this is for t = 3 hour
        }
        else
        {
            dP_dt = change / 4; // divide by 4 as this is the difference in time from 0 value
        }
        pressureAvg = pressureAvg2; // Equating the pressure at 0 to the pressure at 2 hour after 3 hours have past.
        firstRound = false; // flag to let you know that this is on the past 3 hour mark. Initialized to 0 outside main loop.
    }

    int forecast = UNKNOWN;
    if (minuteCount < 35 && firstRound) //if time is less than 35 min on the first 3 hour interval.
    {
        forecast = UNKNOWN;
    }
    else if (dP_dt < (-0.25))
    {
        forecast = THUNDERSTORM;
    }
    else if (dP_dt > 0.25)
    {
        forecast = UNSTABLE;
    }
    else if ((dP_dt > (-0.25)) && (dP_dt < (-0.05)))
    {
        forecast = CLOUDY;
    }
    else if ((dP_dt > 0.05) && (dP_dt < 0.25))
    {
        forecast = SUNNY;
    }
    else if ((dP_dt >(-0.05)) && (dP_dt < 0.05))
    {
        forecast = STABLE;
    }
    else
    {
        forecast = UNKNOWN;
    }

    // uncomment when debugging
    Serial.print(F("Forecast at minute "));
    Serial.print(minuteCount);
    Serial.print(F(" dP/dt = "));
    Serial.print(dP_dt);
    Serial.print(F("kPa/h --> "));
    Serial.println(weather[forecast]);

    return forecast;
}

2017-03-09 10:52:56.474 MySensors: Node: 3, Sketch Name: Pressure Sensor
2017-03-09 10:52:56.475 MySensors: Node: 3, Sketch Version: 1.1
2017-03-09 10:52:56.488 (GATEWAY) Temp (Temp)
2017-03-09 10:52:56.497 (GATEWAY) General/Barometer (Baro)
2017-03-09 10:52:56.503 (GATEWAY) General/Barometer (Baro)
2017-03-09 10:53:40.053 MySensors: Node: 3, Sketch Name: Pressure Sensor
2017-03-09 10:53:40.054 MySensors: Node: 3, Sketch Version: 1.1
2017-03-09 10:53:40.067 (GATEWAY) Temp (Temp)
2017-03-09 10:53:40.075 (GATEWAY) General/Barometer (Baro)
2017-03-09 10:53:40.081 (GATEWAY) General/Barometer (Baro)
2017-03-09 10:54:14.102 MySensors: Node: 3, Sketch Name: Pressure Sensor
2017-03-09 10:54:14.104 MySensors: Node: 3, Sketch Version: 1.1
2017-03-09 10:54:14.148 (GATEWAY) Temp (Temp)
2017-03-09 10:54:14.162 (GATEWAY) General/Barometer (Baro)
2017-03-09 10:54:14.172 (GATEWAY) General/Barometer (Baro)
2017-03-09 10:54:26.662 MySensors: Node: 3, Sketch Name: Pressure Sensor
2017-03-09 10:54:26.664 MySensors: Node: 3, Sketch Version: 1.1
2017-03-09 10:54:26.676 (GATEWAY) Temp (Temp)
2017-03-09 10:54:26.685 (GATEWAY) General/Barometer (Baro)
2017-03-09 10:54:26.691 (GATEWAY) General/Barometer (Baro)
2017-03-09 10:54:44.122 MySensors: Node: 3, Sketch Name: Pressure Sensor
2017-03-09 10:54:44.123 MySensors: Node: 3, Sketch Version: 1.1
2017-03-09 10:54:44.136 (GATEWAY) Temp (Temp)
2017-03-09 10:54:44.145 (GATEWAY) General/Barometer (Baro)
2017-03-09 10:54:44.150 (GATEWAY) General/Barometer (Baro)
2017-03-09 10:54:50.417 MySensors: Node: 3, Sketch Name: Pressure Sensor
2017-03-09 10:54:51.225 MySensors: Node: 3, Sketch Version: 1.1
2017-03-09 10:54:51.227 (GATEWAY) Temp (Temp)
2017-03-09 10:54:51.236 (GATEWAY) General/Barometer (Baro)
2017-03-09 10:54:51.242 (GATEWAY) General/Barometer (Baro)
2017-03-09 10:55:55.513 (GATEWAY) General/Barometer (Baro)
2017-03-09 10:58:05.600 (GATEWAY) Temp (Temp)
2017-03-09 10:58:05.608 (GATEWAY) General/Barometer (Baro)
2017-03-09 10:59:10.651 (GATEWAY) Temp (Temp)
2017-03-09 11:01:20.704 (GATEWAY) Temp (Temp)
2017-03-09 11:02:00.701 MySensors: Node: 3, Sketch Name: Pressure Sensor
2017-03-09 11:02:00.702 MySensors: Node: 3, Sketch Version: 1.1
2017-03-09 11:02:00.715 (GATEWAY) Temp (Temp)
2017-03-09 11:02:00.723 (GATEWAY) General/Barometer (Baro)
2017-03-09 11:02:00.728 (GATEWAY) General/Barometer (Baro)
2017-03-09 11:02:31.650 MySensors: Node: 3, Sketch Name: Pressure Sensor
2017-03-09 11:02:31.652 MySensors: Node: 3, Sketch Version: 1.1
2017-03-09 11:02:31.664 (GATEWAY) Temp (Temp)
2017-03-09 11:02:31.673 (GATEWAY) General/Barometer (Baro)
2017-03-09 11:02:31.678 (GATEWAY) General/Barometer (Baro)
2017-03-09 11:02:38.872 MySensors: Node: 3, Sketch Name: Pressure Sensor
2017-03-09 11:02:38.873 MySensors: Node: 3, Sketch Version: 1.1
2017-03-09 11:02:38.886 (GATEWAY) Temp (Temp)
2017-03-09 11:02:38.894 (GATEWAY) General/Barometer (Baro)
2017-03-09 11:02:38.900 (GATEWAY) General/Barometer (Baro)
2017-03-09 11:02:41.863 MySensors: Node: 3, Sketch Name: Pressure Sensor
2017-03-09 11:02:41.864 MySensors: Node: 3, Sketch Version: 1.1
2017-03-09 11:02:41.887 (GATEWAY) Temp (Temp)
2017-03-09 11:02:41.895 (GATEWAY) General/Barometer (Baro)
2017-03-09 11:02:41.901 (GATEWAY) General/Barometer (Baro)
2017-03-09 11:02:49.208 MySensors: Node: 3, Sketch Name: Pressure Sensor
2017-03-09 11:02:49.209 MySensors: Node: 3, Sketch Version: 1.1
2017-03-09 11:02:49.232 (GATEWAY) Temp (Temp)
2017-03-09 11:02:49.240 (GATEWAY) General/Barometer (Baro)
2017-03-09 11:02:49.245 (GATEWAY) General/Barometer (Baro)
2017-03-09 11:03:54.286 (GATEWAY) General/Barometer (Baro)
2017-03-09 11:04:59.319 (GATEWAY) General/Barometer (Baro)
2017-03-09 11:06:04.359 (GATEWAY) Temp (Temp)
2017-03-09 11:06:04.368 (GATEWAY) General/Barometer (Baro)
2017-03-09 11:06:36.109 MySensors: Node: 3, Sketch Name: Pressure Sensor
2017-03-09 11:06:36.111 MySensors: Node: 3, Sketch Version: 1.1
2017-03-09 11:06:36.123 (GATEWAY) Temp (Temp)
2017-03-09 11:06:36.132 (GATEWAY) General/Barometer (Baro)
2017-03-09 11:06:36.137 (GATEWAY) General/Barometer (Baro)

mfalkvidd

The node sends the data received from the bmp180, so everything seems to be correct. Could you clarify what you expected?

James Flosse

The pressure and temperature is incorrect xD. sorry, i have 20°C in my room and the METAR of the near airport say 1016 hPa.

mfalkvidd

@James-Flosse thanks :)
Strange problem. Is the bmp getting stable power? Maybe it is defective? You don't happen to have another bmp to compare with?

James Flosse

Only bmp180 connected to arduino and i have test with 3 other :s

ghislain

Hi, i'm using this sketch and I had to modify it a little bit. But i'm at work and i haven't it.

You defined the altitude to 688 meters in you sketch, are you sure, you said you're at 1014mbars. If you're really at 700m you should be near 930mbars not 1014mbars.

James Flosse

Ok i defined the altitude by my own (225 meters) but i have the same pressure and temperature :S

ghislain

Too bad, can you upload a basic example sketch in the library adafruit to read pressure and temperature, just to be sure there is the same behavior.

James Flosse

#include <Wire.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_BMP085_U.h>
   
Adafruit_BMP085_Unified bmp = Adafruit_BMP085_Unified(10085);
 
void setup(void) 
{
  Serial.begin(9600);
  Serial.println("Pressure Sensor Test"); Serial.println("");
  
  /* Initialise the sensor */
  if(!bmp.begin())
  {
    /* There was a problem detecting the BMP085 ... check your connections */
    Serial.print("Ooops, no BMP085 detected ... Check your wiring or I2C ADDR!");
    while(1);
  }
}
 
void loop(void) 
{
  /* Get a new sensor event */ 
  sensors_event_t event;
  bmp.getEvent(&event);
 
  /* Display the results (barometric pressure is measure in hPa) */
  if (event.pressure)
  {
    /* Display atmospheric pressure in hPa */
    Serial.print("Pressure: "); Serial.print(event.pressure); Serial.println(" hPa");
  }
  else
  {
    Serial.println("Sensor error");
  }
  delay(250);
}

Pressure: 756.46 hPa
Pressure: 756.47 hPa
Pressure: 756.49 hPa
Pressure: 756.44 hPa
Pressure: 756.44 hPa
Pressure: 756.46 hPa
Pressure: 756.41 hPa
Pressure: 756.44 hPa
Pressure: 756.42 hPa
Pressure: 756.39 hPa
Pressure: 756.42 hPa
Pressure: 756.44 hPa
Pressure: 756.38 hPa
Pressure: 756.40 hPa
Pressure: 756.41 hPa
Pressure: 756.38 hPa
Pressure: 756.41 hPa
Pressure: 756.40 hPa
Pressure: 756.38 hPa
Pressure: 756.40 hPa
Pressure: 756.42 hPa
Pressure: 756.34 hPa
Pressure: 756.22 hPa
Pressure: 756.33 hPa
Pressure: 756.37 hPa
Pressure: 756.38 hPa

same pressure

ghislain

Where did you buy your bmp180 ? you said the 3 you have make the same behavior ? something is wrong with the BMP sensor.

James Flosse

I bought it in banggood, but it work's before...

ghislain

It worked for a while and now it doesn't ? no problem of power supply ? 3v3 ?

James Flosse

I supply itwith the 3.3 V output off arduino

ghislain

I supply it with 5v, are you sure it's a 3v3 version ?

James Flosse

i tested with 3.3V and 5volt but same result
http://www.banggood.com/fr/GY-68-BMP180-Digital-Barometric-Pressure-Sensor-Board-Module-p-1059025.html?rmmds=myorder

ghislain

OK, i've no further idea to help you. But i think your sensor is dead. DId you try older or newer library to compile your project ?

💬 Atmospheric Pressure Sensor

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