File content as of revision 17:97a16bf2ff43:

/*
 * Demonstrates sending a buffer repeatedly to the DAC using DMA.
 * Connect an oscilloscope to Mbed pin 18. This example doesn't
 * output anything else (nothing on any serial ports).
 */
#include "mbed.h"
#include "MODDMA.h"

// Make the buffer size match the number of degrees
// in a circle since we are going to output a sinewave.
#define BUFFER_SIZE 360

// Set DAC output power mode.
#define DAC_POWER_MODE  (1 << 16)

DigitalOut led1(LED1);
DigitalOut led3(LED3);
DigitalOut led4(LED4);

int buffer[2][BUFFER_SIZE];

AnalogOut signal(p18);

MODDMA dma;
MODDMA_Config *conf0, *conf1;

void TC0_callback(void);
void ERR0_callback(void);

void TC1_callback(void);
void ERR1_callback(void);

int main() {
    volatile int life_counter = 0;
    
    // Create a sinewave buffer for testing.
    for (int i =   0; i <=  90; i++) buffer[0][i] =  (512 * sin(3.14159/180.0 * i)) + 512;                
    for (int i =  91; i <= 180; i++) buffer[0][i] =  buffer[0][180 - i];
    for (int i = 181; i <= 270; i++) buffer[0][i] =  512 - (buffer[0][i - 180] - 512);
    for (int i = 271; i <  360; i++) buffer[0][i] =  512 - (buffer[0][360 - i] - 512);
    
    // Adjust the sinewave buffer for use with DAC hardware.
    for (int i = 0; i < 360; i++) {
        buffer[0][i] = DAC_POWER_MODE | ((buffer[0][i] << 6) & 0xFFC0);
        buffer[1][i] = buffer[0][i]; // Just create a copy of buffer0 to continue sinewave.
    }
    
    // Prepare the GPDMA system for buffer0.
    conf0 = new MODDMA_Config;
    conf0
     ->channelNum    ( MODDMA::Channel_0 )
     ->srcMemAddr    ( (uint32_t) &buffer[0] )
     ->dstMemAddr    ( MODDMA::DAC )
     ->transferSize  ( 360 )
     ->transferType  ( MODDMA::m2p )
     ->dstConn       ( MODDMA::DAC )
     ->attach_tc     ( &TC0_callback )
     ->attach_err    ( &ERR0_callback )     
    ; // config end
    
    
    // Prepare the GPDMA system for buffer1.
    conf1 = new MODDMA_Config;
    conf1
     ->channelNum    ( MODDMA::Channel_1 )
     ->srcMemAddr    ( (uint32_t) &buffer[1] )
     ->dstMemAddr    ( MODDMA::DAC )
     ->transferSize  ( 360 )
     ->transferType  ( MODDMA::m2p )
     ->dstConn       ( MODDMA::DAC )
     ->attach_tc     ( &TC1_callback )
     ->attach_err    ( &ERR1_callback )     
    ; // config end

    
    // Calculating the transfer frequency:
    // By default, the Mbed library sets the PCLK_DAC clock value
    // to 24MHz. One complete sinewave cycle in each buffer is 360
    // points long. So, for a 1Hz wave we would need to transfer 360
    // values per second. That would be 24000000/360 which is approx
    // 66,666. But that's no good! The count val is only 16bits in size
    // so bare this in mind. If you need to go slower you will need to
    // alter PCLK_DAC from CCLK/4 to CCLK/8.
    // For our demo we are going to have the sinewave run at 1kHz.
    // That's 24000000/360000 which is approx 66. Experimentation
    // however showed 65 to get closer to 1kHz (on my Mbed and scope 
    // at least).
    LPC_DAC->DACCNTVAL = 65; // 6500 for 10Hz

    // Prepare first configuration.
    if (!dma.Prepare( conf0 )) {
        error("Doh!");
    }
    
    // Begin (enable DMA and counter). Note, don't enable
    // DBLBUF_ENA as we are using DMA double buffering.
    LPC_DAC->DACCTRL |= (3UL << 2);
    
    while (1) { 
        // There's not a lot to do as DMA and interrupts are
        // now handling the buffer transfers. So we'll just
        // flash led1 to show the Mbed is alive and kicking.
        if (life_counter++ > 1000000) {
            led1 = !led1; // Show some sort of life.
            life_counter = 0;
        }
    } 
}

// Configuration callback on TC
void TC0_callback(void) {
    
    // Just show sending buffer0 complete.
    led3 = !led3; 
        
    // Get configuration pointer.
    MODDMA_Config *config = dma.getConfig();
    
    // Finish the DMA cycle by shutting down the channel.
    dma.Disable( (MODDMA::CHANNELS)config->channelNum() );
   
    // Swap to buffer1
    dma.Prepare( conf1 );

    // Clear DMA IRQ flags.
    if (dma.irqType() == MODDMA::TcIrq) dma.clearTcIrq(); 
}

// Configuration callback on Error
void ERR0_callback(void) {
    error("Oh no! My Mbed EXPLODED! :( Only kidding, go find the problem");
}

// Configuration callback on TC
void TC1_callback(void) {
    
    // Just show sending buffer1 complete.
    led4 = !led4; 
        
    // Get configuration pointer.
    MODDMA_Config *config = dma.getConfig();
    
    // Finish the DMA cycle by shutting down the channel.
    dma.Disable( (MODDMA::CHANNELS)config->channelNum() );
    
    // Swap to buffer0
    dma.Prepare( conf0 );
    
    // Clear DMA IRQ flags.
    if (dma.irqType() == MODDMA::TcIrq) dma.clearTcIrq(); 
}

// Configuration callback on Error
void ERR1_callback(void) {
    error("Oh no! My Mbed EXPLODED! :( Only kidding, go find the problem");
}