165 lines
4.0 KiB
C
165 lines
4.0 KiB
C
/*
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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 <wiringPi.h>
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#include <wiringPiSPI.h>
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#include "gertboard.h"
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// The A-D convertor won't run at more than 1MHz @ 3.3v
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#define SPI_ADC_SPEED 1000000
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#define SPI_DAC_SPEED 1000000
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#define SPI_A2D 0
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#define SPI_D2A 1
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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 (const int chan, const int value)
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{
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uint8_t spiData [2] ;
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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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spiData [0] = chanBits ;
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spiData [1] = dataBits ;
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wiringPiSPIDataRW (SPI_D2A, spiData, 2) ;
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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 (const int chan)
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{
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uint8_t spiData [2] ;
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uint8_t chanBits ;
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if (chan == 0)
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chanBits = 0b11010000 ;
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else
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chanBits = 0b11110000 ;
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spiData [0] = chanBits ;
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spiData [1] = 0 ;
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wiringPiSPIDataRW (SPI_A2D, spiData, 2) ;
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return ((spiData [0] << 8) | (spiData [1] >> 1)) & 0x3FF ;
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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 (wiringPiSPISetup (SPI_A2D, SPI_ADC_SPEED) < 0)
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return -1 ;
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if (wiringPiSPISetup (SPI_D2A, SPI_DAC_SPEED) < 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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* New wiringPi node extension methods.
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*********************************************************************************
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*/
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static int myAnalogRead (struct wiringPiNodeStruct *node, const int chan)
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{
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return gertboardAnalogRead (chan - node->pinBase) ;
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}
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static void myAnalogWrite (struct wiringPiNodeStruct *node, const int chan, const int value)
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{
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gertboardAnalogWrite (chan - node->pinBase, value) ;
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}
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/*
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* gertboardAnalogSetup:
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* Create a new wiringPi device node for the analog devices on the
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* Gertboard. We create one node with 2 pins - each pin being read
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* and write - although the operations actually go to different
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* hardware devices.
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*********************************************************************************
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*/
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int gertboardAnalogSetup (const int pinBase)
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{
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struct wiringPiNodeStruct *node ;
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int x ;
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if (( x = gertboardSPISetup ()) != 0)
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return x;
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node = wiringPiNewNode (pinBase, 2) ;
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node->analogRead = myAnalogRead ;
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node->analogWrite = myAnalogWrite ;
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return 0 ;
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}
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