c - microSD卡在SPI模式下计时

我在SPI模式下读写SD卡上的值。512字节块的写入和读取频率设置为10Mhz。写一个块大约需要5毫秒，两个块之间的时间大约是10毫秒。
有没有办法提高写作速度？

void sd_card_write_block(uint16 blockNumber, uint8* buffer)
{
  uint16 blockLow = 0;
  uint16 blockHigh = 0;
  uint8 dummy = 0;
  uint8 result = 0;
  uint8 data_block_start_byte = 0;
  uint8 write_command[SD_CMD_SIZE] = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00};
  uint8 dummy_buffer[DUMMY_BUFFER_LENGTH] = {0xFF, 0xFF, 0xFF, 0xFF,0xFF, 0xFF, 0xFF, 0xFF};
  uint8 i = 0;
  uint8 check_response[CHECK_RESPONSE_SIZE] = {0x00, 0x00, 0x00};
  uint8 check_response1[CHECK_RESPONSE_SIZE] = {0x00, 0x00, 0x00};
  uint8 r1 = 0;
  uint16 retry = 0;
  uint8 response1 = 0;

  dummy = 0xFF;
  //initialize the dummy buffer to keep MOSI pin High
  for(i = 0; i < DUMMY_BUFFER_LENGTH; i++)
  {
    dummy_buffer[i] = 0xFF;
  }

  //set CS pin low
  spi_select_slave( &spi_master_instance, &slave, true);

  //send three clock cycles with MOSI HIGH (Ncs)
  spi_write_buffer_wait( &spi_master_instance, dummy_buffer, NCS_LENGTH);

  //block size was set in sd_init
  blockLow = ((blockNumber & 0x003F) << 9);
  blockHigh = ((blockNumber & 0xFFC0) >> 7);

  //send SD CMD24(WRITE_SINGLE_BLOCK) to write the data to SD card
  write_command[0] = 0x58;

  //high block address bits, blockHigh HIGH and LOW
  write_command[1] = (blockHigh >> 0x08);

  write_command[2] = (blockHigh & 0xFF);
  //low block address bits, blockLow HIGH and LOW
  write_command[3] = (blockLow >> 0x08);
  write_command[4] = (blockLow & 0xFF);

  //checksum is no longer required but send 0xFF
  write_command[5] = 0xFF;

  spi_write_buffer_wait( &spi_master_instance, write_command, SD_CMD_SIZE);


  spi_transceive_buffer_wait( &spi_master_instance, dummy_buffer, check_response, CHECK_RESPONSE_SIZE);

  //send three clock cycles with MOSI High
  spi_write_buffer_wait( &spi_master_instance, dummy_buffer, DUMMY_BUFFER_LENGTH);

  //set bit 0 to 0 which indicates the beginning of the data block
  data_block_start_byte = DATA_BLOCK_START_TOKEN;
  spi_transceive_buffer_wait( &spi_master_instance, &data_block_start_byte, &result, SD_RESPONSE_SIZE);


  /*takes so long because its similar to transreceivea and it discards the rx*/
  spi_write_buffer_wait( &spi_master_instance, buffer, SD_BLOCK_LENGTH);


  //read the microSD card response
  spi_transceive_buffer_wait( &spi_master_instance, dummy_buffer, check_response1, CHECK_RESPONSE_SIZE);

  do
   {
     // write dummy byte
     spi_transceive_buffer_wait( &spi_master_instance, &dummy, &response1, SD_RESPONSE_SIZE);

     r1 = response1;
     // do retry counter
     retry++;
     if(retry > MAX_TIMEOUT)
     {
       spi_select_slave( &spi_master_instance, &slave, false);
       break;
     }
   }
   while(r1 == END_OF_BLOCK_RESPONSE);
  //set the CS High
  spi_select_slave( &spi_master_instance, &slave, false);
}

最佳答案

你不能，至少不能太多。原因是SPI模式本身就是瓶颈。所以，你可以使用一些技巧来提高速度，但你真的不会从中受益太多。如果你真的需要那么快的速度，我建议你使用SDIO（并不像你想象的那么复杂）。如果你用的是AVR，试试xmega的阵容（不要引用我的话，因为我用的是ARMs，所以我在AVR里不太了解），或者完全换成另一个阵容。