Revision 16:cb10aec6feb1, committed 2011-03-14

Comitter:

AjK

Date:

Mon Mar 14 13:51:38 2011 +0000

Parent:

15:e01144bae101

Child:

17:97a16bf2ff43

Commit message:

1.12 See ChangeLoc.c

Changed in this revision

--- a/ChangeLog.c	Mon Mar 14 00:14:24 2011 +0000
+++ b/ChangeLog.c	Mon Mar 14 13:51:38 2011 +0000
@@ -1,8 +1,14 @@
 /* $Id:$
 
+1.12- 14 Mar 2011
+
+    * Added example4.h that demonstrates alternately sending
+      two buffers (double buffering) to the DAC. All those
+      people building MP3 players may find this of interest.
+      
 1.11- 13 Mar 2011
 
-    * Fixed a silly typo in teh documentation of example3.h
+    * Fixed a silly typo in the documentation of example3.h
     
 1.10- 13 Mar 2011
 

--- a/DATALUTS.cpp	Mon Mar 14 00:14:24 2011 +0000
+++ b/DATALUTS.cpp	Mon Mar 14 13:51:38 2011 +0000
@@ -123,7 +123,7 @@
         , (uint8_t)word      // ADC
         , (uint8_t)word      // I2S channel 0
         , (uint8_t)word      // I2S channel 1
-        , (uint8_t)byte      // DAC
+        , (uint8_t)word      // DAC 
         , (uint8_t)byte      // UART0 Tx
         , (uint8_t)byte      // UART0 Rx
         , (uint8_t)byte      // UART1 Tx

--- a/MODDMA.h	Mon Mar 14 00:14:24 2011 +0000
+++ b/MODDMA.h	Mon Mar 14 13:51:38 2011 +0000
@@ -312,7 +312,7 @@
         , p2m = 2UL     /*!< Peripheral to memory - DMA control */
         , p2p = 3UL     /*!< Src peripheral to dest peripheral - DMA control */         
         , g2m = 4UL     /*!< Psuedo special case for reading "peripheral GPIO" that's memory mapped. */
-        , m2g = 5UL     /*!< Psuedo Special case for writing "peripheral GPIO" that's memory mapped. */
+        , m2g = 5UL     /*!< Psuedo Special case for writing "peripheral GPIO" that's memory mapped. */        
     };   
 
     //! Burst size in Source and Destination definitions */
@@ -376,6 +376,20 @@
     void init(bool isConstructorCalling, int Channels = 0xFF, int Tc = 0xFF, int Err = 0xFF);
     
     /**
+     * Used to setup and enable the DMA controller.
+     *
+     * @see Setup
+     * @see Enable
+     * @ingroup API
+     * @param c A pointer to an instance of MODDMA_Config to setup.
+     */
+    uint32_t Prepare(MODDMA_Config *c) {
+        uint32_t u = Setup(c);
+        if (u) Enable(c);
+        return u;
+    }
+    
+    /**
      * Used to setup the DMA controller to prepare for a data transfer.
      *
      * @ingroup API

--- a/SETUP.cpp	Mon Mar 14 00:14:24 2011 +0000
+++ b/SETUP.cpp	Mon Mar 14 13:51:38 2011 +0000
@@ -60,7 +60,7 @@
                 | CxControl_DI() 
                 | CxControl_I();
             break;
-            
+        
         // Memory to peripheral
         case m2p:
             // Assign physical source

--- a/example3.h	Mon Mar 14 00:14:24 2011 +0000
+++ b/example3.h	Mon Mar 14 13:51:38 2011 +0000
@@ -29,7 +29,7 @@
 bool dmaTransferComplete;
 
 MODDMA dma;
-MODDMA_Config *conf, conf_copy;
+MODDMA_Config *conf;
 
 void TC0_callback(void);
 void ERR0_callback(void);

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/example4.h	Mon Mar 14 13:51:38 2011 +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");
+}