57 lines
1.8 KiB
C
57 lines
1.8 KiB
C
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// spi.c
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//
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// Example program for bcm2835 library
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// Shows how to interface with SPI to transfer a byte to and from an SPI device
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//
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// After installing bcm2835, you can build this
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// with something like:
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// gcc -o spi spi.c -l bcm2835
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// sudo ./spi
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//
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// Or you can test it before installing with:
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// gcc -o spi -I ../../src ../../src/bcm2835.c spi.c
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// sudo ./spi
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//
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// Author: Mike McCauley
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// Copyright (C) 2012 Mike McCauley
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// $Id: RF22.h,v 1.21 2012/05/30 01:51:25 mikem Exp $
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#include <bcm2835.h>
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#include <stdio.h>
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int main(int argc, char **argv)
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{
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// If you call this, it will not actually access the GPIO
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// Use for testing
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// bcm2835_set_debug(1);
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if (!bcm2835_init())
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{
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printf("bcm2835_init failed. Are you running as root??\n");
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return 1;
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}
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if (!bcm2835_spi_begin())
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{
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printf("bcm2835_spi_begin failed. Are you running as root??\n");
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return 1;
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}
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bcm2835_spi_setBitOrder(BCM2835_SPI_BIT_ORDER_MSBFIRST); // The default
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bcm2835_spi_setDataMode(BCM2835_SPI_MODE0); // The default
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bcm2835_spi_setClockDivider(BCM2835_SPI_CLOCK_DIVIDER_65536); // The default
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bcm2835_spi_chipSelect(BCM2835_SPI_CS0); // The default
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bcm2835_spi_setChipSelectPolarity(BCM2835_SPI_CS0, LOW); // the default
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// Send a byte to the slave and simultaneously read a byte back from the slave
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// If you tie MISO to MOSI, you should read back what was sent
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uint8_t send_data = 0x23;
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uint8_t read_data = bcm2835_spi_transfer(send_data);
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printf("Sent to SPI: 0x%02X. Read back from SPI: 0x%02X.\n", send_data, read_data);
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if (send_data != read_data)
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printf("Do you have the loopback from MOSI to MISO connected?\n");
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bcm2835_spi_end();
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bcm2835_close();
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return 0;
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}
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