147 lines
4.3 KiB
C
147 lines
4.3 KiB
C
//
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// Gertboard Demo
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//
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// SPI control code
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//
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// This code is part of the Gertboard test suite
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// These routines access the DA chip
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//
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//
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// Copyright (C) Gert Jan van Loo & Myra VanInwegen 2012
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// No rights reserved
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// You may treat this program as if it was in the public domain
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
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// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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// POSSIBILITY OF SUCH DAMAGE.
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//
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//
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// Try to strike a balance between keep code simple for
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// novice programmers but still have reasonable quality code
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//
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#include "gb_common.h"
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#include "gb_spi.h"
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// Set GPIO pins to the right mode
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// DEMO GPIO mapping:
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// Function Mode
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// GPIO0= unused
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// GPIO1= unused
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// GPIO4= unused
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// GPIO7= SPI chip select B Alt. 0
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// GPIO8= unused
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// GPIO9= SPI MISO Alt. 0
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// GPIO10= SPI MOSI Alt. 0
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// GPIO11= SPI CLK Alt. 0
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// GPIO14= unused
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// GPIO15= unused
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// GPIO17= unused
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// GPIO18= unused
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// GPIO21= unused
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// GPIO22= unused
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// GPIO23= unused
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// GPIO24= unused
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// GPIO25= unused
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//
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// For D to A we only need the SPI bus and SPI chip select B
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void setup_gpio()
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{
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INP_GPIO(7); SET_GPIO_ALT(7,0);
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INP_GPIO(9); SET_GPIO_ALT(9,0);
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INP_GPIO(10); SET_GPIO_ALT(10,0);
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INP_GPIO(11); SET_GPIO_ALT(11,0);
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} // setup_gpio
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//
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// Read ADC input 0 and show as horizontal bar
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//
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void main(void)
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{ int d, chan, dummy;
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do {
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printf ("Which channel do you want to test? Type 0 or 1.\n");
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chan = (int) getchar();
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(void) getchar(); // eat carriage return
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} while (chan != '0' && chan != '1');
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chan = chan - '0';
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printf ("These are the connections for the digital to analogue test:\n");
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printf ("jumper connecting GP11 to SCLK\n");
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printf ("jumper connecting GP10 to MOSI\n");
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printf ("jumper connecting GP9 to MISO\n");
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printf ("jumper connecting GP7 to CSnB\n");
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printf ("Multimeter connections (set your meter to read V DC):\n");
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printf (" connect black probe to GND\n");
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printf (" connect red probe to DA%d on J29\n", chan);
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printf ("When ready hit enter.\n");
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(void) getchar();
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// Map the I/O sections
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setup_io();
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// activate SPI bus pins
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setup_gpio();
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// Setup SPI bus
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setup_spi();
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// Most likely, the DAC you have installed is an 8 bit one, not 12 bit so
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// it will ignore that last nibble (4 bits) we send down the SPI interface.
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// So the number that we pass to write_dac will need to be the number
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// want to set (between 0 and 255) multiplied by 16. In hexidecimal,
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// we just put an extra 0 after the number we want to set.
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// So if we want to set the DAC to 64, this is 0x40, so we send 0x400
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// to write_dac.
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// To calculate the voltage we get out, we use this formula from the
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// datasheet: V_out = (d / 256) * 2.048
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d = 0x000;
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write_dac(chan, d);
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// V_out = 0 / 256 * 2.048 (gives 0)
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printf ("Your meter should read about 0V\n");
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printf ("When ready hit enter.\n");
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(void) getchar();
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d = 0x400;
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write_dac(chan, d);
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// V_out = 64 / 256 * 2.048 (gives 0.512)
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printf ("Your meter should read about 0.5V\n");
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printf ("When ready hit enter.\n");
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(void) getchar();
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d = 0x7F0;
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write_dac(chan, d);
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// V_out = 127 / 256 * 2.048 (gives 1.016)
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printf ("Your meter should read about 1.02V\n");
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printf ("When ready hit enter.\n");
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(void) getchar();
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d = 0xAA0;
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write_dac(chan, d);
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// V_out = 170 / 256 * 2.048 (gives 1.36)
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printf ("Your meter should read about 1.36V\n");
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printf ("When ready hit enter.\n");
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(void) getchar();
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d = 0xFF0;
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write_dac(chan, d);
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// V_out = 255 / 256 * 2.048 (gives 2.04)
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printf ("Your meter should read about 2.04V\n");
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printf ("When ready hit enter.\n");
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(void) getchar();
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restore_io();
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} // main
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