Plays USB Audio packets through external DAC (Cirrus Logic CS4344). Simple demo code, don't expect a sophisticated I2S library. HW setup: mbed DIP 5 (I2STX_SDA) -> DAC SDIN (Serial Audio Data Input) mbed DIP 6 (I2STX_WS) -> DAC LRCK (Left Right Clock) mbed DIP 7 (I2STX_CLK) -> DAC SCLK (External Serial Clock Input) mbed DIP 30 (I2SRX_CLK) -> DAC MCLK (Master Clock) also needed an extra USB connector wired to mbed. Does not work with built-in USB. Code needs a bit of clean up.
Diff: I2S.cpp
- Revision:
- 0:bf9e7b99dda5
diff -r 000000000000 -r bf9e7b99dda5 I2S.cpp --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/I2S.cpp Mon Apr 16 08:28:42 2012 +0000 @@ -0,0 +1,145 @@ +#include "I2S.h" +#include "MODDMA.h" + + +volatile uint32_t counter=0; + +DigitalOut led3(LED3); + +//Serial *global_out; +MODDMA dma; +MODDMA_Config *dmaconfig; + +void TC0_callback(void); +void TC1_callback(void); +void TC2_callback(void); + +#define BUFFER_SIZE 2048 + +int16_t buffer[BUFFER_SIZE]; + +int16_t transferSize; + +int16_t *bufferStart, *nextToPlay; +volatile int16_t playing = 0; + +volatile int16_t moreToPlay=0; + +void setup(Serial *out) { + +global_out = out; + + bufferStart = nextToPlay = (int16_t *)buffer; + + LPC_SC->PCONP |= 1 <<27; // Enable I2S + LPC_SC->PCLKSEL1 |= 1 << 22; // Set Clock to CCLK + // Reset i2s + LPC_I2S->I2SDAO = (1 << 4); + LPC_I2S->I2SDAO = 0; + + + + LPC_I2S->I2SDAO = 1 /* Number of bytes 16bit */ | 0xF << 6 /* Word select half perion - 1 */;// | 1 << 3 /* Stop bit */; + LPC_I2S->I2SDAI = 1 /* Number of bytes 16bit */ | 0xF << 6 /* Word select half perion - 1 */;// | 1 << 3 /* Stop bit */; + + + LPC_PINCON->PINSEL0 |= 01 << 14 /* I2STX_CLK */ | 01 << 16 /* I2STX_WS */ | 01 << 18 /* I2STX_SDA */; + LPC_PINCON->PINSEL0 |= 01 << 8 /* I2SRX_CLK */ | 01 << 10 /* I2SRX_WS */ | 01 << 12 /* I2SRX_SDA */; + + // Set all to neither pull-up, nor pull-down + LPC_PINCON->PINMODE0 |= 2 << 14 /* I2STX_CLK */ | 2 << 16 /* I2STX_WS */ | 2 << 18 /* I2STX_SDA */; + LPC_PINCON->PINMODE0 |= 2 << 8 /* I2SRX_CLK */ | 2 << 10 /* I2SRX_WS */ | 2 << 12 /* I2SRX_SDA */; + + + // Cirrus Logic CS4344 specific frequency settings + LPC_I2S->I2STXRATE = 125 /* Y_divider */ | 4 << 8 /* X_divider */; + LPC_I2S->I2SRXRATE = 125 /* Y_divider */ | 32 << 8 /* X_divider */; + + int rxbitrate = 1; + LPC_I2S->I2STXBITRATE = 1; + LPC_I2S->I2SRXBITRATE = rxbitrate; + + + LPC_I2S->I2STXMODE = (0 << 0) | (1 << 3); + LPC_I2S->I2SRXMODE = (0 << 0) | (1 << 3); + + + // Start trasnmit + LPC_I2S->I2SDAO &= (~(1 << 3)); + LPC_I2S->I2SDAI &= (~(1 << 3)); + + LPC_I2S->I2SDMA1 = (1 << 1) /* Enable transit */ | (0 << 16) /* Transmit FIFO level */; + + + out->printf("I2S Setup complete\n"); + + dmaconfig = new MODDMA_Config; + dmaconfig + ->channelNum ( MODDMA::Channel_0 ) +// ->srcMemAddr ( (uint32_t) &buffer1 ) + ->dstMemAddr ( 0 ) + //->transferSize ( 2500 ) + ->transferType ( MODDMA::m2p ) + ->transferWidth ( 1 ) + ->srcConn ( 0 ) + ->dstConn ( MODDMA::I2S_Channel_0 ) + ->dmaLLI ( 0 ) + ->attach_tc ( &TC1_callback ) + ; + + out->printf("DMA Setup complete\n"); + +} + + +void play(int16_t *buf,int16_t length) { + + + moreToPlay = 1; + + if (nextToPlay - bufferStart + length >= BUFFER_SIZE) { + nextToPlay = bufferStart; + } + + memcpy(nextToPlay,buf,length*sizeof(int16_t)); + + transferSize=length; + + + // Wait for end of playing previous packet + while (playing) {}; + + playing = 1; + moreToPlay = 0; + + dmaconfig->srcMemAddr ( (uint32_t) nextToPlay ); + dmaconfig->transferSize ( length / 2); + nextToPlay+=length*sizeof(int16_t); + + + dma.Prepare(dmaconfig); + + +} + + + +void TC1_callback(void) { + + // Get configuration pointer. + MODDMA_Config *config = dma.getConfig(); + + // Finish the DMA cycle by shutting down the channel. + dma.Disable( (MODDMA::CHANNELS)config->channelNum() ); + + + // Clear DMA IRQ flags. + if (dma.irqType() == MODDMA::TcIrq) dma.clearTcIrq(); + + playing = 0; + + if (!moreToPlay) { + LPC_I2S->I2STXFIFO = 0x0; + led3 = !led3; + } +}