Mischa Megens / DMAFuncGen

Function generator using the DAC output, using DMA alone.

Dependents:   DACDMAfuncgenlib

This library has been inspired by MODDMA example4.h.

Some differences compared with the MODDMA example: 1) this DMAFuncGen class can work using dma alone (no ISR required, although there is a callback routine included if you would like to synchronize something to the function generator), and 2) there is only one buffer (not two).

It is intended for the LPC1768. It has been tested and seems to work fine.

For a demo program, see

Import programDACDMAfuncgenlib

Generate a sine wave on the Analog Output using DMA alone.

Last commit 29 Dec 2013 by Mischa Megens

DMAFuncGen.h

Committer:
Mischa
Date:
2013-12-29
Revision:
0:337ad0fe7734

File content as of revision 0:337ad0fe7734:

#ifndef MBED_DMAFUNCGEN_H
#define MBED_DMAFUNCGEN_H

#include "mbed.h"
#include "MODDMA.h"

//! DMAFuncGen class generates a waveform on Analog output using Direct Memory Access alone.
class DMAFuncGen {
public:
    /// Create DMAFucGen instance
    /// @param dma The dma to use.
    /// @param channel The dma channel to use for transferring data to the D/A converter.
    DMAFuncGen(MODDMA& dma, MODDMA::CHANNELS channel);

    /// Number of data points in the waveform. Must be set by client.
    int buffer_size;
    /// Buffer for the binary data that will be transferred by DMA. Must be allocated by client.
    uint32_t* buffer;

    /// Set waveform value for a specified data point.
    /// @param idx The index of the data point in #buffer, must be in range 0..#buffer_size-1.
    /// @param x The value for the D/A, in the range 0..65535.
    void set(int idx, uint16_t x);
    /// Get waveform value for a specified data point
    /// @param idx The index of the data point in the #buffer, in the range 0..#buffer_size-1.
    /// @returns The value for the data point, in the range 0..65535.
    uint16_t operator[](const uint16_t idx);
    
    /// Connect the D/A converter pin (enable output)
    void Connect();
    /// Disconnect the D/A converter pin (pin becomes tri-state)
    void Disconnect();

    /// Reference to the DMA instance   
    MODDMA& dma;
    
    /// Set up the dma.
    /// Must set #buffer and #buffer_size first.
    void Setup(void);
    
    /// Set waveform frequency
    /// @note Must set #buffer_size first.
    /// @param f Frequency of a complete cycle of the waveform (in Hz). 
    void SetFrequency(float f);
    /// Read the actual waveform frequency that will be generated.
    float Frequency();
    
    /// Start generating the waveform (start dma)
    void Start();
    /// Stop generating the waveform (but waits for the current cycle to complete)
    void Stop();

private:
    MODDMA_Config conf;
    MODDMA_LLI lli;

    /// ISR routine, called on Terminal Count
    void TC_callback(void);
    /// ISR routine, called on dma ERRor
    void ERR_callback(void);
};

#endif