e-paper-display/bcm2835-1.71/examples/spin/spin.c

64 lines
2.2 KiB
C

// spin.c
//
// Example program for bcm2835 library
// Shows how to interface with SPI to transfer a number of bytes to and from an SPI device
//
// After installing bcm2835, you can build this
// with something like:
// gcc -o spin spin.c -l bcm2835
// sudo ./spin
//
// Or you can test it before installing with:
// gcc -o spin -I ../../src ../../src/bcm2835.c spin.c
// sudo ./spin
//
// Author: Mike McCauley
// Copyright (C) 2012 Mike McCauley
// $Id: RF22.h,v 1.21 2012/05/30 01:51:25 mikem Exp $
#include <bcm2835.h>
#include <stdio.h>
int main(int argc, char **argv)
{
// If you call this, it will not actually access the GPIO
// Use for testing
// bcm2835_set_debug(1);
if (!bcm2835_init())
{
printf("bcm2835_init failed. Are you running as root??\n");
return 1;
}
if (!bcm2835_spi_begin())
{
printf("bcm2835_spi_begin failed. Are you running as root??\n");
return 1;
}
bcm2835_spi_begin();
bcm2835_spi_setBitOrder(BCM2835_SPI_BIT_ORDER_MSBFIRST); // The default
bcm2835_spi_setDataMode(BCM2835_SPI_MODE0); // The default
bcm2835_spi_setClockDivider(BCM2835_SPI_CLOCK_DIVIDER_65536); // The default
bcm2835_spi_chipSelect(BCM2835_SPI_CS0); // The default
bcm2835_spi_setChipSelectPolarity(BCM2835_SPI_CS0, LOW); // the default
// Send a some bytes to the slave and simultaneously read
// some bytes back from the slave
// Most SPI devices expect one or 2 bytes of command, after which they will send back
// some data. In such a case you will have the command bytes first in the buffer,
// followed by as many 0 bytes as you expect returned data bytes. After the transfer, you
// Can the read the reply bytes from the buffer.
// If you tie MISO to MOSI, you should read back what was sent.
char buf[] = { 0x01, 0x02, 0x11, 0x33 }; // Data to send
bcm2835_spi_transfern(buf, sizeof(buf));
// buf will now be filled with the data that was read from the slave
printf("Read from SPI: %02X %02X %02X %02X \n", buf[0], buf[1], buf[2], buf[3]);
bcm2835_spi_end();
bcm2835_close();
return 0;
}