wayne roberts / Mbed OS alarm_master

Alarm generator, transmitter side

Dependencies:   sx12xx_hal

radio chip selection

Radio chip driver is not included, allowing choice of radio device.
If you're using SX1272 or SX1276, then import sx127x driver into your program.
if you're using SX1261 or SX1262, then import sx126x driver into your program.
if you're using SX1280, then import sx1280 driver into your program.
If you're using NAmote72 or Murata discovery, then you must import only sx127x driver.

This is transmitter project; Receiver side is Alarm Slave project.
This project generates alarm (transmits) from grounding certain pins.
To find the actual pins used, refer to the code where pin[A-D] is declared as DigitalIn.

Alarm message is sent N times with future timestamp indicating when alarm is to occur. This accommodates dropped packets, resulting in alarm occurring when as few as 1 packet is received.

main.cpp

Committer:
dudmuck
Date:
2017-08-22
Revision:
0:cb38da4f4b04
Child:
1:3199506bc2e5

File content as of revision 0:cb38da4f4b04:

#include "sx127x_lora.h"
 
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;
    }
}
/**********************************************************************/

DigitalIn user_button(USER_BUTTON);
Timer t;
#define CMD_ALARM       0x01

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 transmit(unsigned target)
{
    unsigned t_diff;
    uint16_t crc;

    radio.tx_buf[0] = CMD_ALARM;
    t_diff = target - t.read_us();
    radio.tx_buf[1] = t_diff >> 24;
    radio.tx_buf[2] = t_diff >> 16;
    radio.tx_buf[3] = t_diff >> 8;
    radio.tx_buf[4] = t_diff & 0xff;
    crc = crc_ccitt(radio.tx_buf, 5);
    radio.tx_buf[5] = crc >> 8;
    radio.tx_buf[6] = crc & 0xff;


    lora.start_tx(lora.RegPayloadLength);   /* begin transmission */

    while (lora.service() != SERVICE_TX_DONE)   /* wait for transmission to complete */
        ;

    printf("t_diff:%u crc:%04x\r\n", t_diff, crc);
}

#define TARGET_LATENCY      2000000
void send_alarm()
{
    int i;
    unsigned target = t.read_us() + TARGET_LATENCY;
    printf("send_alarm() %u\n", target);

    for (i = 0; i < 3; i++) {
        transmit(target);
        wait(0.1);
    }
}
 
int main()
{
    printf("\r\nreset-tx\r\n");
    t.start();
    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);
                
    /* constant payload length */
    lora.RegPayloadLength = 7;
    radio.write_reg(REG_LR_PAYLOADLENGTH, lora.RegPayloadLength);

    for (;;) {       
        if (!user_button.read()) {
            int i;
            for (i = 0; i < 5; i++) {
                wait(0.01);
                if (user_button.read()) {
                    printf("trans\r\n");
                    break;
                }
            }
            if (i == 5)
                send_alarm();

            while (!user_button.read())
                ;
        }

    } // ..for (;;)
}