SignalGenDAC.h

00001 //
00002 // Signal Generator DAC Driver
00003 //
00004 // Derived from AN10917: Memory to DAC data transfers using the LPC1700's DMA
00005 //
00006 // 
00007 #ifndef SIGNALGENDAC_H
00008 #define SIGNALGENDAC_H
00009 
00010 #include "mbed.h"
00011 
00012 #include "SignalGenDefs.h"       // access the waveform mode data type
00013 
00014 
00015 #define SIGNAL_MEM_ENTRIES 2048     // size of the DAC buffer
00016 
00017 /// The Signal Generator DAC Driver
00018 ///
00019 /// This class provides the interface to first configure the DAC hardware characteristics,
00020 /// and then to define and control the DAC output.
00021 ///
00022 /// A choice of waveforms is available (Sine, Square, Triangle, Sawtooth, and User Defined.
00023 ///
00024 /// @todo add support for User Defined waveform.
00025 ///
00026 /// @code
00027 /// SignalGenDAC g_signal;            // defaults to LPC1768 mbed module (p18 and 3.3v)
00028 /// 
00029 /// g_signal.PrepareWaveform(SG_SINE, 1000, 50, 2.2, 1.5);
00030 /// g_signal.Start();
00031 /// wait_ms(1000);
00032 /// g_signal.Stop();
00033 /// @endcode
00034 ///
00035 class SignalGenDAC {
00036 
00037 public:
00038 
00039     /// Constructor, which is used to define the hardware
00040     /// 
00041     /// The default parameters are based on the mbed LPC1768 micro, which has
00042     /// AnalogOut on p18 and uses a 3.3v supply for the A/D reference.
00043     ///
00044     /// @param[in] aout is the analog output pin
00045     /// @param[in] minV is based on the A/D low reference voltage (default 0.0)
00046     /// @param[in] maxV is based on the A/D high reference voltage (default 3.3)
00047     ///
00048     SignalGenDAC(PinName aout = p18, float minV = 0.0, float maxV = 3.3);
00049 
00050     /// Destructor
00051     ///
00052     ~SignalGenDAC();
00053 
00054     /// Create the waveform in the private memory buffer that is used to DMA to the DAC
00055     ///
00056     /// @param[in] mode defines the waveform: Sine, Square, Triangle, Sawtooth, User
00057     /// @param[in] frequency defines the desired frequency
00058     /// @param[in] dutycycle defined the duty cycle of the waveform to be created. The value
00059     ///             is range limited to 5 to 95 (representing 5 to 95 %).
00060     /// @param[in] voltage is the peak-to-peak voltage, and it range limited to 0 to 3.0.
00061     /// @param[in] offset is the offset voltage, and is range limited to 0 to 3.0.
00062     ///
00063     void PrepareWaveform(SG_Waveform mode, float frequency, float dutycycle, float voltage, float offset);
00064 
00065     /// Start the signal, in either a oneshot, or continuous mode.
00066     ///
00067     /// @param[in] oneShot defaults false, which causes continuous mode. 
00068     ///             When set true, one cycle is produced.
00069     ///
00070     void Start(bool oneShot = false);
00071 
00072     /// Stop the signal, if it is running.
00073     ///
00074     void Stop(void);
00075 
00076     /// Determine if the signal is running.
00077     ///
00078     /// @returns true if the signal is running.
00079     ///
00080     bool isRunning(void) { return isOn; }
00081 
00082 private:
00083     bool isOn;              // tracks whether the signal is on or off
00084     AnalogOut * aout;
00085     float frequency;        // signal parameters
00086     float dutycycle;
00087     float voltage;
00088     float offset;
00089     float minV;             // Based on the A/D hardware
00090     float maxV;             // Based on the A/D hardware
00091     /// range limit a value.
00092     float rangelimit(float value, float min, float max);
00093     int numSamples;         // private container for number of samples
00094 };
00095 
00096 #endif // SIGNALGENDAC_H