ArduinoExample.ino

#include <Arduino.h>
#include <Wire.h>
#include "SerialPnP.h"

// This global variable dictates the sample rate.
uint32_t g_SampleRate = 1000; // default = 1000ms

// Tracks time of last sample in Arduino ticks
uint32_t g_LastSample = 0;

// This function will be called by SerialPnP to both read and update the sample
// rate of the temperature. The schema of the property data is `SerialPnPSchema_Int`
// as defined on initialization, so the method signature is defined accordingly.
void
CbSampleRate(
    int32_t     *input,
    int32_t     *output
)
{
    // If input variable is defined, validate and update sample rate variable
    if (input) {
        // Only allow sample rates between 100ms and 10s
        if ((*input > 100) && (*input <= 10000)) {
            g_SampleRate = *input;
        }
    }

    // Output will always be defined for a property callback
    *output = g_SampleRate;
}

// This function handles calibration and will return success or failure as a bool.
void
CbCalibrate(
    int32_t     *inputTemperature,
    int32_t     *outputSuccess
)
{
    *outputSuccess = *inputTemperature << 1;
}

void setup() {
    SerialPnP_Setup("Example Thermometer");

    // This begins configuration of a new Azure PnP interface, backed by the
    // provided URI.
    SerialPnP_NewInterface("http://contoso.com/thermometer_example");

    // This provides an event, which will be periodically sent by the device to
    // provide a temperature measurement.
    SerialPnP_NewEvent("temperature",                          // short ID for the event
                       "Ambient Temperature",                  // friendly name for event
                       "A sample of the ambient temperature.", // description of event
                       SerialPnPSchema_Float,                  // data schema for temperature data
                       "celsius");                             // units of the temperature data

    // This provides a property which the gateway may use to configure the sample rate
    // for the temperature data.
    SerialPnP_NewProperty("sample_rate",                             // short ID for property
                          "Sample Rate",                             // friendly name for property
                          "Sample Rate of temperature measurements", // description of property
                          "ms",                                      // unit of sample rate is millisecond
                          SerialPnPSchema_Int,                       // data schema of property
                          false,                                     // required
                          true,                                      // writeable by gateway
                          (SerialPnPCb*) CbSampleRate);              // callback - see below

    // This provides a calibration method which allows the gateway to provide an ambient
    // temperature for calibration purposes.
    SerialPnP_NewCommand("calibrate",                                // short ID for command
                         "Calibrate Temperature",                    // friendly name for command
                         "Calibrates the thermometer",               // description of command
                         SerialPnPSchema_Int,                      // data schema of input to command
                         SerialPnPSchema_Int,                    // data schema of output to command
                         (SerialPnPCb*) CbCalibrate);                // callback - see below
}

void loop() {
    g_LastSample = millis();
    while(1) {
        SerialPnP_Process();
        uint32_t cticks = millis();

        if (cticks - g_LastSample < g_SampleRate) {
            continue;
        }

        SerialPnP_SendEventFloat("temperature", 12.34f);
        g_LastSample = cticks;
    }
}