GPDMA (Direct Memory Access) and LLI (Link List Item) test see: http://mbed.org/users/okini3939/notebook/dma_jp/
MODDMA/example4.h
- Committer:
- okini3939
- Date:
- 2013-09-13
- Revision:
- 0:de79d4a48e63
File content as of revision 0:de79d4a48e63:
/* * 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"); }