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OPL-Transmitter.C

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Code:
/* RASPBERRY PI One-Page LoRa TRANSMITTER
*
*  AI Ra-01_V1.0 Semtech SX1278
*
*  LoRa            Pi
*  3.3V         3.3V    Red
*  GND            GND        Black
*  SCK            SCLK    Yellow
*  MOSI            MOSI    Green
*  MISO            MISO    Orange
*  NSS            CE0    White
*  RESET        #18    Brown
*  DIO0    ------1k------- #24    Grey IRQ pulled down + 1k current limiter
*  Pi3.3V--button--1k--> #17    STOP button pulled DOWN + 1k current limiter
*/

#include <bcm2835.h>
#include <stdio.h>

const int reset = 18;
const int irq = 24;
const int button = 17;

void SXSetup(void)            
{
    char buf[2];
        
    bcm2835_gpio_write(reset,LOW);              // reset low  100us
    delayMicroseconds(100);
    bcm2835_gpio_write(reset,HIGH);
    delay(10);                                // time to reset,  minimum 5ms
    
    buf[0] = 0x81; buf[1] = 0x00;               // sleep mode
    bcm2835_spi_transfern(buf, sizeof(buf));
    
    buf[0] = 0x81; buf[1] = 0x88;               // LoRa, low frequency mode
    bcm2835_spi_transfern(buf, sizeof(buf));
        
    buf[0] = 0x89; buf[1] = 0xF3;               // PA_BOOST
    bcm2835_spi_transfern(buf, sizeof(buf));
            
    buf[0] = 0x91; buf[1] = 0xF7;               // Setup for TX_Done interrupt
    bcm2835_spi_transfern(buf, sizeof(buf));
    
}

void clear_LoRa_interrupts(void)
{    
    char buf[2];
    buf[0] = 0x92; buf[1] = 0xFF;               
    bcm2835_spi_transfern(buf, sizeof(buf));
}    
    
void send(void)
{
    char buf[2];
    char data = 0;
    
    while(!bcm2835_gpio_lev(button))         // while button not pressed
    {
    
        buf[0] = 0x81; buf[1] = 0x09;            // standby to set up packet             
        bcm2835_spi_transfern(buf, sizeof(buf));

        buf[0] = 0x8D; buf[1] = 0x80;            // Transmitter base address   
        bcm2835_spi_transfern(buf, sizeof(buf)); // Set SPI fifo pointer

        buf[0] = 0x80; buf[1] = data;               
        bcm2835_spi_transfern(buf, sizeof(buf)); // Write packet to fifo

        buf[0] = 0x81; buf[1] = 0x8B;               
        bcm2835_spi_transfern(buf, sizeof(buf)); // TX on, LF mode (send)
        
        delay(100);
        
        buf[0] = 0x12; buf[1] = 0x00;               
        bcm2835_spi_transfern(buf, sizeof(buf)); // Get RegIrqFlags
    
        if (buf[1])                              // If RegIrqFlags != 0 then TXDone
        {
            printf("Sent %d \n",data);       // so byte has been sent
            clear_LoRa_interrupts();
        }
        
        buf[0] = 0x81; buf[1] = 0x88;               
        bcm2835_spi_transfern(buf, sizeof(buf)); // TX and RX to sleep, clear fifo
    
        delay(900);                    // Wait a ~sec before sending next byte 
        
        if (data<10){ 
            data++;
        }
        else
        {
            data = 0;
        }
    }
}
    
int main(int argc, char **argv)
{
    if (!bcm2835_init())
        {
            printf("bcm2835_init failed. Root?\n");
            return 1;
        }

    if (!bcm2835_spi_begin())
        {
            printf("bcm2835_spi_begin failed. Root?\n");
            return 1;
        }

    bcm2835_gpio_fsel(reset,BCM2835_GPIO_FSEL_OUTP);         // Reset pin is output
    bcm2835_gpio_write(reset,HIGH);                          // Reset active low
    
    bcm2835_gpio_fsel(irq,BCM2835_GPIO_FSEL_INPT);           // IRQ pin is input (from DIO0)
    bcm2835_gpio_set_pud(irq,BCM2835_GPIO_PUD_DOWN);         // Pulled DOWN
            
    bcm2835_gpio_fsel(button,BCM2835_GPIO_FSEL_INPT);        // Button is input 
    bcm2835_gpio_set_pud(button,BCM2835_GPIO_PUD_DOWN);      // Pulled DOWN
         
    SXSetup();

    clear_LoRa_interrupts();
    
    printf("Ready to send data. Press button to quit... \n");
    
    send();
                
    bcm2835_spi_end();
    bcm2835_close();
    printf("================= Clean-up DONE ================ \n");
    return 0;

}

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