// SPI peripheral setup
Baudrate: DIV128 (HSI 16MHz -> 125kHz)
Clock polarity: Low on idle
Clock phase: First transition
DDF: 8 bits
FF: MSB first
SSI and SSM: enabled
Frame std: Motorola
Role: Master

// This is the init sequence
delay_ms(1000);

cs_high();
for (u32 i = 0; i < 30; ++i)
{
  WAIT_UNTIL(spi_is_flag_set(SPI1, SPI_FLAG_TX_BUF_EMPTY));
  spi_data_write(SPI1, 0xff);
}

u8 cmd0[] = {
  0x40, 0x00, 0x00, 0x00, 0x00, 0x95
};

cs_low();
send_spi_cmd(cmd0);
u8 r1 = get_spi_resp();
cs_high();

if (r1 != 0x01)
{
  while (1);
}

u8 cmd8[] = {
  0x48, 0x00, 0x00, 0x01, 0xaa, 0x87
};

cs_low();

send_spi_cmd(cmd8);
r1 = get_spi_resp();
u32 r7[4];
for (u32 i = 0; i < 4; ++i)
{
  spi_data_write(SPI1, 0xff);
  WAIT_UNTIL(spi_is_flag_set(SPI1, SPI_FLAG_RX_BUF_NOT_EMPTY));
  WAIT_UNTIL(spi_is_flag_set(SPI1, SPI_FLAG_BUSY) == 0);
  r7[i] = spi_data_read(SPI1);
}

cs_high();
// r7 = 0x00, 0x00, 0x01, 0xaa

u8 cmd58[] = { 0x7a, 0x00, 0x00, 0x00, 0x00, 0xfd };

cs_low();
send_spi_cmd(cmd58);
r1 = get_spi_resp();
u8 ocr[4];
for (u32 i = 0; i < 4; ++i)
{
  spi_data_write(SPI1, 0xff);
  WAIT_UNTIL(spi_is_flag_set(SPI1, SPI_FLAG_RX_BUF_NOT_EMPTY));
  WAIT_UNTIL(spi_is_flag_set(SPI1, SPI_FLAG_BUSY) == 0);
  ocr[i] = spi_data_read(SPI1);
}
cs_high();
// OCR = 0x00, 0xff, 0x80, 0x00

u8 cmd55[] = { 0x77, 0x0, 0x0, 0x0, 0x0, 0x65 };
u8 acmd41[] = { 0x69, 0x00, 0x00, 0x00, 0x00, 0x5f };

while (1)
{
  cs_low();
  send_spi_cmd(cmd55);
  u8 cmd55_r = get_spi_resp();
  cs_high();

  if (cmd55_r != 0x01)
  {
    // Error
    break;
  }

  delay_ms(100);

  cs_low();
  send_spi_cmd(acmd41);
  u8 acmd41_r = get_spi_resp();
  cs_high();

  if (acmd41_r == 0)
  {
    // Card is ready
    break;
  }

  delay_ms(100);
}

// send_spi_cmd() and get_spi_resp()
void
send_spi_cmd(u8* cmd)
{
  for (u32 i = 0; i < 6; ++i)
  {
    WAIT_UNTIL(spi_is_flag_set(SPI1, SPI_FLAG_TX_BUF_EMPTY));
    spi_data_write(SPI1, cmd[i]);

    WAIT_UNTIL(spi_is_flag_set(SPI1, SPI_FLAG_BUSY) == 0);

    WAIT_UNTIL(spi_is_flag_set(SPI1, SPI_FLAG_RX_BUF_NOT_EMPTY));
    (void) spi_data_read(SPI1);
  }
}

u8
get_spi_resp(void)
{
  while (1)
  {
    WAIT_UNTIL(spi_is_flag_set(SPI1, SPI_FLAG_TX_BUF_EMPTY));
    spi_data_write(SPI1, 0xff);

    WAIT_UNTIL(spi_is_flag_set(SPI1, SPI_FLAG_RX_BUF_NOT_EMPTY));
    u8 data = spi_data_read(SPI1);

    if ((data & 0x80) == 0)
    {
      return data;
    }
  }
}