Revision 0:e5edc0373da0, committed 2011-05-07

Comitter:

JLS

Date:

Sat May 07 19:27:14 2011 +0000

Commit message:

Changed in this revision

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/MCP4922.cpp	Sat May 07 19:27:14 2011 +0000
@@ -0,0 +1,156 @@
+/*
+ * MCP4922 - DAC library.
+ */
+
+#include "mbed.h"
+#include "MCP4922.h"
+
+using namespace mbed;
+
+int dac =0;
+
+MCP4922::MCP4922(PinName mosi, PinName sclk, PinName cs) : _spi(mosi, NC, sclk) {
+
+    int i;
+    _ndacs = 1;
+    _ncs_array = new DigitalOut*[ _ndacs ];
+    for (i=0; i<_ndacs; i++) {
+        _ncs_array[i] = new DigitalOut(cs);
+    }
+
+    // Initialise the DAC SPI interface.
+    _init();
+}
+
+// Destructor
+MCP4922::~MCP4922() {
+
+    // Before destroying the object, shut down all the chips.
+    //shdn_all();
+
+    // Delete all the NCS DigitalOut objects and the array pointing to
+    // them.
+    int i;
+    for (i=0; i<_ndacs; i++) {
+        delete _ncs_array[i];
+    }
+    delete [] _ncs_array;
+
+    // Delete the LDAC DigitalOut object if it exists.
+    if (_latched ) delete _nldac;
+}
+
+// Initialise SPI interface.
+void MCP4922::_init() {
+
+    // Set up the SPI for 16-bit values (12-bit + 4 command bits) and mode 0.
+    _spi.format(16, 0);
+
+    // Start with all the CS and LDAC signals high (disabled)
+    int i;
+    for (i=0; i<_ndacs; i++) {
+        _ncs_array[i]->write(1);
+    }
+
+    if (_latched ) _nldac->write(1);
+    return;
+}
+
+// Set SPI clock frequency.
+void MCP4922::frequency( int freq ) {
+
+    // Set the SPI interface clock frequency in Hz.
+    _spi.frequency( freq );
+    return;
+}
+
+/*
+ * Note: There is a lot of code in common between the following 4 functions.
+ * The code is kept in line to keep it efficient. Could the functions have
+ * been written as templates?
+ */
+// Write to DAC channel A with gain 1.
+void MCP4922::writeA(int value) {
+
+    // Set up the command register with the appropriate value.
+    // For efficiency, the caller is assumed to have checked dac.
+    int reg;
+    //int dac = 0;
+    reg = (value & 0x0FFF) | MCP4922_REG_A1;
+
+    // Select the DAC chip, write to its command register and
+    // then unselect the DAC chip.
+    _ncs_array[dac]->write(0);
+    _spi.write(reg);
+    _ncs_array[dac]->write(1);
+    return;
+}
+
+// Write to DAC channel B with gain 1.
+void MCP4922::writeB(int value) {
+
+    // Set up the command register with the appropriate value.
+    // For efficiency, the caller is assumed to have checked dac.
+    int reg;
+    reg = (value & 0x0FFF) | MCP4922_REG_B1;
+
+    // Select the DAC chip, write to its command register and then
+    // unselect the DAC chip.
+    _ncs_array[dac]->write(0);
+    _spi.write(reg);
+    _ncs_array[dac]->write(1);
+    return;
+}
+
+// Write an array of values to the DACs.
+void MCP4922::write(int nchans, int values[], int gain, int latch) {
+
+    // nchans must be at least 1 but less than or equal to ndacs x 2.
+    if (nchans < 1) nchans = 1;
+    const int maxchans = _ndacs * 2;
+    if (nchans > maxchans) nchans = maxchans;
+
+    if (latch && _latched)
+        latch_disable();
+
+    int i;
+
+        for (i=0; i<nchans;) {
+            dac = i/2;
+            writeA(values[i]);
+            i++;
+            if (i < nchans) {
+                writeB(values[i]);
+                i++;
+            } else break;
+        }
+
+    // Automatically latch the new voltages if the latch flag is 1.
+    if (latch && _latched)
+        latch_enable();
+    return;
+}
+
+// Set latch signal to "enable".
+void MCP4922::latch_enable() {
+
+    // Latch all chips. There should be a delay of at least T_LS=40
+    // nanoseconds between the last CS rising edge and the LDAC falling
+    // edge. The software function calls seem to be sufficient to
+    // introduce that delay. A delay may be inserted here if this
+    // software is ported to a faster processor.
+    if (_latched) _nldac->write(0);
+    // The LDAC pulse width must be at least T_LD=100 nanoseconds long.
+    // A delay can be inserted here if necessary, but so far this has
+    // not been needed (see above).
+    return;
+}
+
+// Set latch signal to "disable".
+void MCP4922::latch_disable() {
+
+    // Disable latch for all chips.
+    if (_latched) _nldac->write(1);
+    return;
+}
+

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/MCP4922.h	Sat May 07 19:27:14 2011 +0000
@@ -0,0 +1,80 @@
+/*
+ * MCP4922 - DAC library.
+ *
+ * Copyright (c) 2011 Steven Beard, UK Astronomy Technology Centre.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "mbed.h"
+
+#ifndef MCP4922_H
+#define MCP4922_H
+
+/* Reference: Microchip Technology (2005), MCP4821/MCP4822 DAC Data Sheet. */
+
+// MCP4922 reference voltage.
+#define MCP4922_VREF     2048    // Reference voltage (mV)
+
+/* Define possible combinations of 16-bit command register bits */
+#define MCP4922_REG_A1   0x3000  // Channel A gain 1
+#define MCP4922_REG_B1   0xB000  // Channel B gain 1
+#define MCP4922_REG_SHDN 0x0000  // Output power down
+
+class MCP4922 {
+public:
+
+    MCP4922 (PinName mosi, PinName sclk, PinName cs);
+
+    ~MCP4922();
+
+    /*+
+     * frequency: Set the SPI bus clock frequency in Hz.
+     *        The SPI bus frequency in Hz. Must be within the range
+     *        supported by both the SPI interface and the DAC chips
+     *        (~10 KHz to 20 MHz).
+     */
+    void frequency( int freq );
+    
+    void writeA(int value );
+    
+    void writeB(int value );
+
+    void write( int nchans, int values[], int gain=2, int latch=1 );
+
+    void latch_enable();
+    
+    void latch_disable();
+
+private:
+    
+    MCP4922( const MCP4922& rhs );
+    
+    void _init();
+
+    int _ndacs;              // The number of DACS in the array
+    int _latched;            // Is the "not LDAC" pin used (1=yes; 0=no)?
+    SPI _spi;                // SPI bus object for communicating with DAC.
+    DigitalOut** _ncs_array; // Array of pointers to DigitalOut objects
+    // connected to "not CS" pins.
+    DigitalOut* _nldac;      // Pointer to DigitalOut object connected
+    // to "not LDAC" pin (if any - NULL if none).
+};
+
+#endif

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Sat May 07 19:27:14 2011 +0000
@@ -0,0 +1,47 @@
+#include "mbed.h"
+#include "MCP4922.h"
+
+MCP4922 MCP(p5, p7,p8);  // MOSI, SCLK, CS
+
+int main() {
+
+    MCP.frequency(1000000);
+
+    float x = 0.5;
+    float y = 0.25;
+    float z = 0.125;
+    float oldx = 0;
+    float oldy = 0;
+    float oldz = 0;
+        
+    float dt = 0.005;
+    
+    float alpha = 15.6;
+    float beta = 28.58;
+    float a = -1.14286;
+    float b = -0.714286;
+    float h = 0;
+    
+    int xout = 0;
+    int yout = 0;
+
+    while (1) {
+
+    oldx = x;
+    oldy = y;
+    oldz = z;
+
+    h = (b * x) + (0.5 * (a - b) * (abs(x+1) - abs(x-1)));
+                
+    x = oldx + dt * (alpha * (oldy - oldx - h));
+    y = oldy + dt * (oldx - oldy + oldz);
+    z = oldz + dt * (-beta * oldy);
+    
+    xout = 2047+(850*x);        
+    yout = 2047+6*(800*y);
+   
+    MCP.writeA(xout);
+    MCP.writeB(yout);
+
+    }
+}
\ No newline at end of file

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mbed.bld	Sat May 07 19:27:14 2011 +0000
@@ -0,0 +1,1 @@
+http://mbed.org/users/mbed_official/code/mbed/builds/63bcd7ba4912