STM32F4 Audio Capture using FatFs SD

[muhammaduzairafzal45]

Posted on December 16, 2014 at 21:02

I am facing problem in capturing and saving audio .wav file to SD card using DMA and SDIO interface. I am using STM32F4 discovery. The loopback works fine. I am using I2S sampling rate of 32k. Problem arrives when writing to SD. I am using buffer size of 1024 now which was initially 8192. I figured out after spending a week that FatFs library work only if i write 512 bytes  on SD.If i write more data like 8k buffer,it randomly skips huge chunks of data. Also i notices that it takes 20ms max to write 512 bytes(write cycle varies from 5ms to 20ms) on SD using SDIO which i think is horribly slow speed.I am now writing 1024 bytes by writing 512 bytes in ping pong method but data is skipping and audio is barely recognized.Note that i am writing to file in main while loop when DMA buffer is filled in ping pong method.I tried to write data in DMA ISR but it SDIO stuck during writes which i think is due to fast speed of incoming data so i moved to while loop.Can somebody tell me why cannot i write more than 512 bytes at once on SD and why is SDIO speed so slow.SD card is of good quality? Basic chunks of code is copied below. Thanks,

int16_t array_pong[512];/* CODEC_I2S peripheral configuration for master TX */SPI_I2S_DeInit(CODEC_I2S);I2S_InitStructure.I2S_AudioFreq = 32000;I2S_InitStructure.I2S_Standard = I2S_Standard_Phillips;I2S_InitStructure.I2S_DataFormat = I2S_DataFormat_16b;//extended;I2S_InitStructure.I2S_CPOL = I2S_CPOL_Low;I2S_InitStructure.I2S_Mode = I2S_Mode_MasterTx;I2S_InitStructure.I2S_MCLKOutput = I2S_MCLKOutput_Enable;/* Initialize the I2S main channel for TX */I2S_Init(CODEC_I2S, &I2S_InitStructure);void DMA1_Stream3_IRQHandler(void){  int16_t *src, *dst, sz; GPIO_ToggleBits(GPIOC, GPIO_Pin_1); total_time++; /* Transfer complete interrupt */ if (DMA_GetFlagStatus(AUDIO_I2S_EXT_DMA_STREAM, AUDIO_I2S_EXT_DMA_FLAG_TC) != RESET) { /* Point to 2nd half of buffers */ sz = szbuf/2; src = (int16_t *)(rxbuf) + sz; dst = (int16_t *)(txbuf) + sz; WaveCounter += sz; //I2S_RX_CallBack(src, dst, sz, 0);   ping_complete = 1; /* Clear the Interrupt flag */ DMA_ClearFlag(AUDIO_I2S_EXT_DMA_STREAM, AUDIO_I2S_EXT_DMA_FLAG_TC); } /* Half Transfer complete interrupt */ if (DMA_GetFlagStatus(AUDIO_I2S_EXT_DMA_STREAM, AUDIO_I2S_EXT_DMA_FLAG_HT) != RESET) { /* Point to 1st half of buffers */ sz = szbuf/2; src = (int16_t *)(rxbuf); dst = (int16_t *)(txbuf); WaveCounter += sz; //I2S_RX_CallBack(src, dst, sz, 1); pong_complete = 1; /* Clear the Interrupt flag */ DMA_ClearFlag(AUDIO_I2S_EXT_DMA_STREAM, AUDIO_I2S_EXT_DMA_FLAG_HT);     }}while(1){ if(total_time >= 2000) { I2S_Cmd(CODEC_I2S, DISABLE); I2S_Cmd(CODEC_I2S_EXT, DISABLE); break; } if(ping_complete == 1) { f_write (&file, (int16_t*)array_pong+256, 512, (void *)&bw); ping_complete =0; } if(pong_complete == 1) { f_write (&file,(int16_t *) array_pong, 512, (void *)&bw); pong_complete =0; } __nop; __nop; __nop; __nop; __nop; __nop; } #dma #stm32 #fatfs #sdio #sd