File content as of revision 0:b6ec8db2edbf:

#include "sx127x_lora.h"
 
DigitalOut myled(LED1);
 
SPI spi(D11, D12, D13); // mosi, miso, sclk
//           dio0, dio1, nss, spi, rst
SX127x radio(  D2,   D3, D10, spi, A0); // sx1276 arduino shield
 
SX127x_lora lora(radio);
DigitalInOut rfsw(A4);    // for SX1276 arduino shield
 
void rfsw_callback()
{
    if (radio.RegOpMode.bits.Mode == RF_OPMODE_TRANSMITTER)
        rfsw = 1;
    else
        rfsw = 0;
}
/**********************************************************************/
DigitalOut pc_3(PC_3);
Timeout to;

#define PIN_ASSERT_us       200000
#define CMD_ALARM       0x01

void alarm_pin_clr()
{
    pc_3 = 0;
}

void alarm_pin_set()
{
    pc_3 = 1;
    to.attach_us(&alarm_pin_clr, PIN_ASSERT_us);
}

static uint16_t crc_ccitt( uint8_t *buffer, uint16_t length )
{
    // The CRC calculation follows CCITT
    const uint16_t polynom = 0x1021;
    // CRC initial value
    uint16_t crc = 0x0000;

    if( buffer == NULL )
    {
        return 0;
    }

    for( uint16_t i = 0; i < length; ++i )
    {
        crc ^= ( uint16_t ) buffer[i] << 8;
        for( uint16_t j = 0; j < 8; ++j )
        {
            crc = ( crc & 0x8000 ) ? ( crc << 1 ) ^ polynom : ( crc << 1 );
        }
    }

    return crc;
}

void get_alarm()
{
    uint16_t rx_crc, crc = crc_ccitt(radio.rx_buf, 5);
    rx_crc = radio.rx_buf[5];
    rx_crc <<= 8;
    rx_crc += radio.rx_buf[6];
    //printf("%u) crc rx:%04x, calc:%04x\r\n", lora.RegRxNbBytes, rx_crc, crc);
    if (crc == rx_crc) {
        if (radio.rx_buf[0] == CMD_ALARM) {
            unsigned delay;
            delay = radio.rx_buf[1];
            delay <<= 8;
            delay += radio.rx_buf[2];
            delay <<= 8;
            delay += radio.rx_buf[3];
            delay <<= 8;
            delay += radio.rx_buf[4];
            to.attach_us(&alarm_pin_set, delay);
            printf("delay:%u\r\n", delay);
        } else
            printf("cmd? %02x\r\n", radio.rx_buf[0]);
    } else
        printf("crc fail %04x, %04x\r\n", rx_crc, crc);
}
 
int main()
{   
    printf("\r\nreset-rx\r\n");
    radio.rf_switch = rfsw_callback;
    
    radio.set_frf_MHz(910.8);
    lora.enable();
    lora.setBw_KHz(500);
    lora.setSf(11);
    
    /* RFO or PABOOST choice:
     * SX1276 shield: RFO if using 900MHz, or PA_BOOST if using 433MHz
     */
    rfsw.input();
    if (rfsw.read()) {
        printf("LAS\r\n");
        /* LAS HF=PA_BOOST  LF=RFO */
        if (radio.HF)
            radio.RegPaConfig.bits.PaSelect = 1;
        else
            radio.RegPaConfig.bits.PaSelect = 0;
    } else {
        /* MAS shield board, only RFO TX */
        radio.RegPaConfig.bits.PaSelect = 0;
        printf("MAS\r\n");
    }
    rfsw.output();
    radio.write_reg(REG_PACONFIG, radio.RegPaConfig.octet);
                
    lora.start_rx(RF_OPMODE_RECEIVER);
    
    for (;;) {     
        if (lora.service() == SERVICE_READ_FIFO) {
            /*int i;
            for (i = 0; i < lora.RegRxNbBytes; i++) {
                printf("%02x ", radio.rx_buf[i]);
            }
            printf("\r\n");*/
            get_alarm();
        }
    }
}