File content as of revision 7:803a185d7021:

#include "radio.h"
#include "mbed.h"
#include "platform/CircularBuffer.h"
#include "MbedJSONValue/MbedJSONValue.h"

// Semtech radio definitions for SX127x, SX126x and SX128x

#if defined(SX127x_H)
    #define BW_KHZ              500
    #define SPREADING_FACTOR    11
    #define CF_HZ               912000000
    #define TX_DBM              20
#elif defined(SX126x_H)
    #define BW_KHZ              500
    #define SPREADING_FACTOR    10
    #define CF_HZ               915000000
    #define TX_DBM              (Radio::chipType == CHIP_TYPE_SX1262 ? 20 : 14) 
#elif defined(SX128x_H)
    #define BW_KHZ              200
    #define SPREADING_FACTOR    7
    #define CF_HZ               2487000000
    #define TX_DBM              6
#endif

// The buffer size should match the tx_buf length in sx12xx.h
#define BUF_SIZE    256

/******************** Setup radio transmitter ****************************/

// Analog Sensor setup
AnalogIn sensor_light(A1);
AnalogIn sensor_temp(A3);
double light_val_analog;
double temperature_analog;

// Configure the User button as an interrupt
InterruptIn button(USER_BUTTON, PullUp);

// Initialize global variables
uint8_t seq = 0;  //  Set initial transmit sequence to 0
volatile bool txDone;
CircularBuffer<uint8_t, BUF_SIZE> msg;
MbedJSONValue message;
Timer t;

// Forward declaration
float convert_analog_light_resistance(double analog_val);
float convert_analog_temperature(double analog_val);

// Transmit Done Callback Handler
void txDoneCB()
{
    txDone = true;
    printf("Tx Done.\r\n");
}

// Receive Done Callback Handler
void rxDoneCB(uint8_t size, float rssi, float snr)
{
    printf("Rx Done.\r\n");
}

// Transmit Timeout Callback Handler
void txTimeoutCB()
{
    printf("Tx Timeout.\r\n");
}

// Define radio events for transmitter
const RadioEvents_t rev = {
    /* Dio0_top_half */     NULL,
    /* TxDone_topHalf */    NULL,
    /* TxDone_botHalf */    txDoneCB,
    /* TxTimeout  */        txTimeoutCB,
    /* RxDone  */           rxDoneCB,
    /* RxTimeout  */        NULL,
    /* RxError  */          NULL,
    /* FhssChangeChannel  */NULL,
    /* CadDone  */          NULL
};

/**
* Interrupt Handler for the User button.
*/
void button_send_json()
{
    string s;
    seq++;
    
    //fill the object
    message["btn_count"] = seq;
    message["btn_timer"] = t.read();
    message["light_val"] = light_val_analog;
    message["light_resistance"] = convert_analog_light_resistance(light_val_analog);
    message["temperature"] = convert_analog_temperature(temperature_analog);
    message["my_str"] = "Hello World!";
    message["my_boolean"] = false;
    
    //serialize it into a JSON string
    s = message.serialize();
    printf("json: %s\r\n", s.c_str());
    
    memcpy(Radio::radio.tx_buf, s.c_str(), s.length());
    txDone = false;
    Radio::Send(s.length(), 0, 0, 0);   // begin transmission of payload
    t.reset();
}

/**
* Function for initializing the SX127x radio.
*/
void radio_init()
{
    // Start radio transmitter after POR or reset
    Radio::Init(&rev);

    //Set radio properties for transmitter
    Radio::Standby();
    Radio::LoRaModemConfig(BW_KHZ, SPREADING_FACTOR, 1);
    Radio::SetChannel(CF_HZ);

    // Set transmitter output power
    Radio::set_tx_dbm(TX_DBM);

    // Setup transmit packet payload  -> preambleLen, fixLen, crcOn, invIQ
    Radio::LoRaPacketConfig(8, false, true, false);
}

float convert_analog_light_resistance(double analog_val)
{          
    float Rsensor=(float)(1023-analog_val)*10/analog_val;
    return Rsensor;
}

float convert_analog_temperature(double analog_val)
{
    double a = analog_val*1023;
    double resistance=(float)(1023-a)*10000/a;
    double temperature=1/(log(resistance/10000)/3975+1/298.15)-276.05;
    double temperature_f = (9.0*temperature)/5.0 + 32.0;
    return temperature_f;
}

int main()
{        
    printf("\r\nreset-tx \n");
    button.fall(&button_send_json);
    
    radio_init();
    
    // Start a timer to track time between button presses
    t.start();

    for (;;)
    {
        // Transmit message on button press, service radio until tx complete.
        while (!txDone)
        {
            Radio::service();
            light_val_analog = sensor_light.read();
            temperature_analog = sensor_temp.read();
        }
    }
}