Greenhouse: Phase 3, Sensors Working

It has been a while since I posted, but a lot has been going on.

As far as this project is concerned, the barometer ended up being a real pain. I was using the Adafruit MPL3115A2 breakout board and, as you can see from the previous post, I tied it in on the same I2C bus as one of the AM2315 Temperature and Humidity Sensors on the DUE. I modified the Adafruit library for the MPL3115A2 in the same way I modified the AM2315 to work on any I2C bus I want it to and fired everything up.

Nothing. Not a peep from the sensor.

I tried it on the second I2C bus.

Nothing.

Now that's annoying. I checked the wiring a bunch of times, checked my code, and yet... nothing.

I then dug out an Arduino UNO to try it out on and everything worked perfectly.

I wrote a post on the forums at Adafruit to see if anyone had any ideas. Someone else tried the MPL3115A2 on a DUE and also never got it to work. So I went over to Sparkfun and bought their same board. I know, kinda silly, but I was hoping it was something about the Adafruit board and that the Sparkfun board would just work. But no, it was not to be and the Sparkfun board remained silent on the DUE. Ultimately the folks at Adafruit decided that something was odd about the DUE I2C libraries just for the barometer board, perhaps a timing issue or something, even if it was working with the temperature/humidity sensors.

Poking around, I found the Teensy 3.1 has 2 I2C buses so gave it a try. Everything worked the first time, though the Teensy libraries do not use the I2C interfaces from twi.h, and I found they had their own I2C library called i2c_t3. So much for uniform library naming.

My final modifications for the Adafruit libraries for the AM2315 and the MPL3115A are found here and here, respectively.

Here is a picture of the final breadboard. I am leaving it as a breadboard for the next year in case I want to add in other sensors. I left it with the Sparkfun barometer board, which is on the right. The left side is the Teensy 3.1.

Below is the Fritzing diagram of the circuit. I couldn't find a part that shows the pins on the underside of the Teensy so just drew the wires with a note to label them. You can see the wires coming out from under the Teensy on its right side in the above picture.

My Arduino sketch is still not sending the binary data to the host processor, but here is the current code.

#include <i2c_t3.h>
#include <Adafruit_AM2315.h>
#include <Adafruit_MPL3115A2.h>

// The inside AM2315 temperature and humidity sensor.
Adafruit_AM2315 am2315Inside(&Wire1);

Adafruit_MPL3115A2 barometric(&Wire1);


// The outside AM2315 temperature and humidity sensor.
Adafruit_AM2315 am2315Outside(&Wire);

// The sensor data packet containing all data to be transmitted
// to the host.
typedef struct _SenseData {
  float temperatureInside;
  float humidityInside;
  float temperatureOutside;
  float humidityOutside;
  float altitude;
  float barometricPressure;
  float barometicTemp;
} SenseData;;

SenseData senseData;

void setup() {
  Serial.begin(9600);
}

void loop() {
 if (am2315Outside.begin()) {
    am2315Outside.readTemperatureAndHumidity(senseData.temperatureOutside, senseData.humidityOutside);
    Serial.print("Outside Hum: "); Serial.println(senseData.humidityOutside);
    Serial.print("Outside Temp: "); Serial.println(senseData.temperatureOutside);
  } else {
    Serial.println("Cannot see outside AM2315");
  }

  if (am2315Inside.begin()) {
    am2315Inside.readTemperatureAndHumidity(senseData.temperatureInside, senseData.humidityInside);
    Serial.print("Inside Hum: "); Serial.println(senseData.humidityInside);
    Serial.print("Inside Temp: "); Serial.println(senseData.temperatureInside);
  } else {
    Serial.println("Cannot see inside AM2315");
  }
 
  if (barometric.begin()) {
    senseData.barometricPressure = barometric.getPressure();
    Serial.print(senseData.barometricPressure/3377); Serial.println(" Inches (Hg)");

    senseData.altitude = barometric.getAltitude();
    Serial.print(senseData.altitude); Serial.println(" meters");

    senseData.barometicTemp = barometric.getTemperature();
    Serial.print(senseData.barometicTemp); Serial.println("*C");
  } else {
    Serial.println("Couldnt find barametric sensor");
  }

  delay(1000);
}

You may notice the conditionals inside the loop that are constantly calling the begin() method for the sensor. I did this so that if a physical sensor is removed, the other sensors can continue to report their data. The else section will probably set those fields to minus infinity or NaN if the sensor is not read.

When I am finally ready to send this to the host computer, I will use a line like

Serial.write(&senseData, sizeof(senseData);

This line will send out the packet with the data in the order that the fields are defined in the structure SenseData above.

In the next installment of the Greenhouse Saga, I will show the Java end that will read the data from the sensor and place it in an Interactive Spaces activity.