137 lines
4.2 KiB
C
137 lines
4.2 KiB
C
//
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// Gertboard test
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//
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// SPI (ADC/DAC) 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 AD and DA chips
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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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//
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// Set-up the SPI interface
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//
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// Speed depends on what you talk to
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// In this case use 1MHz
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//
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void setup_spi()
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{
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// Want to have 1 MHz SPI clock.
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// Assume 250 Mhz system clock
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// So divide 250MHz system clock by 250 to get 1MHz45
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SPI0_CLKSPEED = 250;
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// clear FIFOs and all status bits
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SPI0_CNTLSTAT = SPI0_CS_CLRALL;
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SPI0_CNTLSTAT = SPI0_CS_DONE; // make sure done bit is cleared
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} // setup_spi()
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//
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// Read a value from one of the two ADC channels
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//
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// To understand this code you had better read the
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// datasheet of the AD chip (MCP3002)
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//
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int read_adc(int chan) // 'chan' must be 0 or 1. This is not checked!
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{ unsigned char v1,v2,rec_c;
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int status,w;
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// Set up for single ended, MS comes out first
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v1 = 0xD0 | (chan<<5);
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// Delay to make sure chip select is high for a short while
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short_wait();
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// Enable SPI interface: Use CS 0 and set activate bit
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SPI0_CNTLSTAT = SPI0_CS_CHIPSEL0|SPI0_CS_ACTIVATE;
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// Write the command into the FIFO so it will
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// be transmitted out of the SPI interface to the ADC
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// We need a 16-bit transfer so we send a command byte
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// folowed by a dummy byte
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SPI0_FIFO = v1;
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SPI0_FIFO = 0; // dummy
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// wait for SPI to be ready
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// This will take about 16 micro seconds
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do {
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status = SPI0_CNTLSTAT;
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} while ((status & SPI0_CS_DONE)==0);
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SPI0_CNTLSTAT = SPI0_CS_DONE; // clear the done bit
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// Data from the ADC chip should now be in the receiver
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// read the received data
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v1 = SPI0_FIFO;
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v2 = SPI0_FIFO;
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// Combine the 8-bit and 2 bit values into an 10-bit integer
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// NOT!!! return ((v1<<8)|v2)&0x3FF;
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// I have checked the result and it returns 3 bits in the MS byte not 2!!
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// So I might have my SPI clock/data pahse wrong.
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// For now its easier to dadpt the results (running out of time)
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return ( (v1<<7) | (v2>>1) ) & 0x3FF;
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} // read_adc
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//
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// Write 12 bit value to DAC channel 0 or 1
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//
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// To understand this code you had better read the
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// datasheet of the AD chip (MCP4802/MCP4812/MCP4822)
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//
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void write_dac(int chan, // chan must be 0 or 1, this is not checked
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int val) // chan must be max 12 bit
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{ char v1,v2,dummy;
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int status;
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val &= 0xFFF; // force value in 12 bits
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// Build the first byte: write, channel 0 or 1 bit
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// and the 4 most significant data bits
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v1 = 0x30 | (chan<<7) | (val>>8);
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// Remain the Least Significant 8 data bits
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v2 = val & 0xFF;
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// Delay to have CS high for a short while
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short_wait();
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// Enable SPI: Use CS 1 and set activate bit
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SPI0_CNTLSTAT = SPI0_CS_CHIPSEL1|SPI0_CS_ACTIVATE;
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// send the values
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SPI0_FIFO = v1;
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SPI0_FIFO = v2;
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// wait for SPI to be ready
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// This will take about 16 micro seconds
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do {
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status = SPI0_CNTLSTAT;
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} while ((status & SPI0_CS_DONE)==0);
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SPI0_CNTLSTAT = SPI0_CS_DONE; // clear the done bit
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// For every transmit there is also data coming back
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// We MUST read that received data from the FIFO
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// even if we do not use it!
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dummy = SPI0_FIFO;
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dummy = SPI0_FIFO;
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} // write_dac
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