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185 lines
4.4 KiB
185 lines
4.4 KiB
/*
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* gertboard.c:
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* Access routines for the SPI devices on the Gertboard
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* Copyright (c) 2012 Gordon Henderson
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*
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* The Gertboard has:
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*
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* An MCP3002 dual-channel A to D convertor connected
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* to the SPI bus, selected by chip-select A, and:
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*
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* An MCP4802 dual-channel D to A convertor connected
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* to the SPI bus, selected via chip-select B.
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*
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***********************************************************************
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* This file is part of wiringPi:
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* https://projects.drogon.net/raspberry-pi/wiringpi/
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*
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* wiringPi is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as
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* published by the Free Software Foundation, either version 3 of the
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* License, or (at your option) any later version.
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*
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* wiringPi is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with wiringPi.
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* If not, see <http://www.gnu.org/licenses/>.
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***********************************************************************
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*/
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#include <stdio.h>
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#include <stdint.h>
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#include <fcntl.h>
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#include <sys/ioctl.h>
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#include <linux/spi/spidev.h>
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#include "gertboard.h"
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// The SPI bus parameters
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// Variables as they need to be passed as pointers later on
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static char *spiA2D = "/dev/spidev0.0" ;
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static char *spiD2A = "/dev/spidev0.1" ;
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static uint8_t spiMode = 0 ;
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static uint8_t spiBPW = 8 ;
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static uint32_t spiSpeed = 100000 ; // 1MHz
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static uint16_t spiDelay = 0;
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// Locals here to keep track of everything
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static int spiFdA2D ;
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static int spiFdD2A ;
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/*
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* gertboardAnalogWrite:
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* Write an 8-bit data value to the MCP4802 Analog to digital
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* convertor on the Gertboard.
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*********************************************************************************
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*/
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void gertboardAnalogWrite (int chan, int value)
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{
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uint8_t spiBufTx [2] ;
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uint8_t spiBufRx [2] ;
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struct spi_ioc_transfer spi ;
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uint8_t chanBits, dataBits ;
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if (chan == 0)
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chanBits = 0x30 ;
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else
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chanBits = 0xB0 ;
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chanBits |= ((value >> 4) & 0x0F) ;
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dataBits = ((value << 4) & 0xF0) ;
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spiBufTx [0] = chanBits ;
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spiBufTx [1] = dataBits ;
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spi.tx_buf = (unsigned long)spiBufTx ;
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spi.rx_buf = (unsigned long)spiBufRx ;
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spi.len = 2 ;
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spi.delay_usecs = spiDelay ;
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spi.speed_hz = spiSpeed ;
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spi.bits_per_word = spiBPW ;
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ioctl (spiFdD2A, SPI_IOC_MESSAGE(1), &spi) ;
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}
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/*
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* gertboardAnalogRead:
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* Return the analog value of the given channel (0/1).
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* The A/D is a 10-bit device
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*********************************************************************************
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*/
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int gertboardAnalogRead (int chan)
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{
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uint8_t spiBufTx [4] ;
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uint8_t spiBufRx [4] ;
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struct spi_ioc_transfer spi ;
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uint8_t chanBits ;
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if (chan == 0)
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chanBits = 0b0110100 ;
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else
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chanBits = 0b0111100 ;
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spiBufTx [0] = chanBits ;
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spiBufTx [1] = 0 ;
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spi.tx_buf = (unsigned long)spiBufTx ;
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spi.rx_buf = (unsigned long)spiBufRx ;
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spi.len = 4 ;
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spi.delay_usecs = spiDelay ;
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spi.speed_hz = spiSpeed ;
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spi.bits_per_word = spiBPW ;
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ioctl (spiFdA2D, SPI_IOC_MESSAGE(1), &spi) ;
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return spiBufRx [0] << 8 | spiBufRx [1] ;
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}
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/*
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* setParams:
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* Output the SPI bus parameters to the given device
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*********************************************************************************
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*/
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static int setParams (int fd)
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{
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if (ioctl (fd, SPI_IOC_WR_MODE, &spiMode) < 0)
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return -1 ;
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if (ioctl (fd, SPI_IOC_RD_MODE, &spiMode) < 0)
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return -1 ;
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if (ioctl (fd, SPI_IOC_WR_BITS_PER_WORD, &spiBPW) < 0)
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return -1 ;
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if (ioctl (fd, SPI_IOC_RD_BITS_PER_WORD, &spiBPW) < 0)
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return -1 ;
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if (ioctl (fd, SPI_IOC_WR_MAX_SPEED_HZ, &spiSpeed) < 0)
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return -1 ;
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if (ioctl (fd, SPI_IOC_RD_MAX_SPEED_HZ, &spiSpeed) < 0)
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return -1 ;
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return 0 ;
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}
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/*
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* gertboardSPISetup:
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* Initialise the SPI bus, etc.
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*********************************************************************************
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*/
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int gertboardSPISetup (void)
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{
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if ((spiFdA2D = open (spiA2D, O_RDWR)) < 0)
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return -1 ;
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if (setParams (spiFdA2D) != 0)
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return -1 ;
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if ((spiFdD2A = open (spiD2A, O_RDWR)) < 0)
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return -1 ;
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if (setParams (spiFdD2A) != 0)
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return -1 ;
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return 0 ;
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}
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