Diff: MCP4922.h

Revision:

0:4e1ee1c4d3bb

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/MCP4922.h	Wed Jul 04 01:29:05 2012 +0000
@@ -0,0 +1,80 @@
+#ifndef MCP4922_H
+#define MCP4922_H
+
+#include "DAC_SPI.h"
+
+/** 
+* The MCP4922 is a dual package 12 bit DAC.  We should be able to produce two analog output voltages up to twice the externally wired voltage references (VrefA, VrefB).
+ The maximum voltage output is limited by the input voltage at V_DD which can go up to about 5.5V.  
+
+* Datasheet: http://ww1.microchip.com/downloads/en/DeviceDoc/22250A.pdf
+
+* All serial commands are 16 bit words.   The highest 4 bits are control bits, while the last 12 are the data bits for the 12-bit DAC MCP4822.
+*    + bit 15: select which DAC to use.
+*    + bit 14: 0=buffered , 1= unbuffered
+*    + bit 13: 0= gain x2, 1= gain x1
+*    + bit 12: 0= DAC active, 1= shut down DAC
+*    + bit 11-0: Data bits for the DAC.
+*/
+class MCP4922: public DAC_SPI
+{    
+    public:
+    
+    /** Initializes the MCP 4922 DAC 
+    *
+    * @param SPIchannelNum An int representing the SPI channel used by this DAC
+    * channel 0 for p5 and p7
+    * channel 1 for p11 and p13
+    * @param CS The chip select pin used to identify the device
+    * @param LDAC The LDAC pin used to synchronize updates of multiple devices
+    */
+    MCP4922(int SPIchannelNum, PinName CS,  PinName LDAC);
+    
+    /** Writes a value between 0-4095 to the currently selected DAC output 
+    * @param DACvalue a value from 0-4095 to write to the DAC register
+    */
+    virtual void write(int DACvalue);
+    
+    /** Writes a value in mV to the DAC outputs.
+    * The output will only be accurate if Vref is set to the appropriate voltage reference scaling factor. 
+    * @param millivolte The desired voltage output in millivolts
+    */
+    virtual void write_mV(int millivolts); 
+    
+    /** If automatic updating is disabled, this will update the DAC output on command */
+    void update();    
+    
+    /** select whether to use DAC A or DAC B. 
+    * @param DACnum 0 to modify DAC A, 1 to modify DAC B
+    */
+    virtual void select(char DACnum); 
+    
+    /** If true, the DAC output will update as soon as the output value is modified.  If false, it will wait for an update command*/
+    bool autoUpdate;
+    
+    /** The currently selected DAC channel.  0 for DAC A, 1 for DAC B*/
+    char DACselect;
+    
+    /** The output scaling factor in mV for channel A.
+    * The voltage wired to Vref will be used as the scaling factor which the DAC will use in producing the output voltage.
+    * If using the write_mV function, it is important that Vref is properly set.  This library uses 5000mV by default.
+    */
+    int VrefA;
+    /** The output scaling factor in mV for channel B.
+    * The voltage wired to Vref will be used as the scaling factor which the DAC will use in producing the output voltage.
+    * If using the write_mV function, it is important that Vref is properly set.  This library uses 5000mV by default.
+    */
+    int VrefB;
+    
+    /** Manually set the gain of the DAC.  The only valid values are 1 and 2.   The default gain is x1 to match the wired reference voltage*/
+    void setGain(int gain_value);
+    
+    /** Turn on or off the output buffer.  The default value for the buffer is off.  See section 4.1.2 of the datasheet for more information. */
+    char buffered;
+    
+    private:
+    /** The output gain bit of the DAC.  If set to 0, gain is x2. If set to 1 gain is x1.  The default gain is 1.*/
+    bool gain;
+};
+
+#endif //MCP4922_H
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