Diff: MODDMA/example4.h

Revision:

2:a3e0f7f37ac9

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/MODDMA/example4.h	Wed Dec 05 07:56:09 2012 +0000
@@ -0,0 +1,156 @@
+/*
+ * 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");
+}