64 lines
2.2 KiB
C
64 lines
2.2 KiB
C
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// spin.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 number of bytes 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 spin spin.c -l bcm2835
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// sudo ./spin
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//
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// Or you can test it before installing with:
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// gcc -o spin -I ../../src ../../src/bcm2835.c spin.c
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// sudo ./spin
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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_begin();
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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 some bytes to the slave and simultaneously read
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// some bytes back from the slave
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// Most SPI devices expect one or 2 bytes of command, after which they will send back
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// some data. In such a case you will have the command bytes first in the buffer,
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// followed by as many 0 bytes as you expect returned data bytes. After the transfer, you
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// Can the read the reply bytes from the buffer.
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// If you tie MISO to MOSI, you should read back what was sent.
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char buf[] = { 0x01, 0x02, 0x11, 0x33 }; // Data to send
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bcm2835_spi_transfern(buf, sizeof(buf));
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// buf will now be filled with the data that was read from the slave
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printf("Read from SPI: %02X %02X %02X %02X \n", buf[0], buf[1], buf[2], buf[3]);
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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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