/* Configure I2S for Audio Format input */
Status Chip_I2S_TxConfig(LPC_I2S_T *pI2S, I2S_AUDIO_FORMAT_T *format)
{
uint32_t temp;
uint16_t xDiv, yDiv;
uint32_t N;
if (getClkDiv(pI2S, format, &xDiv, &yDiv, &N) == ERROR) {
return ERROR;
}
temp = pI2S->DAO & (~(I2S_DAO_WORDWIDTH_MASK | I2S_DAO_MONO | I2S_DAO_SLAVE | I2S_DAO_WS_HALFPERIOD_MASK));
if (format->WordWidth <= 8) {
temp |= I2S_WORDWIDTH_8;
}
else if (format->WordWidth <= 16) {
temp |= I2S_WORDWIDTH_16;
}
else {
temp |= I2S_WORDWIDTH_32;
}
temp |= (format->ChannelNumber) == 1 ? I2S_MONO : I2S_STEREO;
temp |= I2S_MASTER_MODE;
temp |= I2S_DAO_WS_HALFPERIOD(format->WordWidth - 1);
pI2S->DAO = temp;
pI2S->TXMODE = I2S_TXMODE_CLKSEL(0);
pI2S->TXBITRATE = N - 1;
pI2S->TXRATE = yDiv | (xDiv << 8);
return SUCCESS;
}
/* Configure I2S for Audio Format input */
Status Chip_I2S_Config(LPC_I2S_T *pI2S, uint8_t TRMode, Chip_I2S_Audio_Format_T *audio_format)
{
uint32_t pClk;
uint32_t x, y;
uint64_t divider;
uint16_t dif;
uint16_t x_divide = 0, y_divide = 0;
uint32_t N;
uint16_t err, ErrorOptimal = 0xFFFF;
Chip_Clock_EnablePeriphClock(SYSCTL_CLOCK_I2S);
#if defined(CHIP_LPC175X_6X)
pClk = Chip_Clock_GetPeripheralClockRate(SYSCTL_PCLK_I2S);
#else
pClk = Chip_Clock_GetPeripheralClockRate();
#endif
/* divider is a fixed point number with 16 fractional bits */
divider = (((uint64_t) (audio_format->SampleRate) * 2 * (audio_format->WordWidth) * 2) << 16) / pClk;
/* find N that make x/y <= 1 -> divider <= 2^16 */
for (N = 64; N > 0; N--) {
if ((divider * N) < (1 << 16)) {
break;
}
}
if (N == 0) {
return ERROR;
}
divider *= N;
for (y = 255; y > 0; y--) {
x = y * divider;
if (x & (0xFF000000)) {
continue;
}
dif = x & 0xFFFF;
if (dif > 0x8000) {
err = 0x10000 - dif;
}
else {
err = dif;
}
if (err == 0) {
y_divide = y;
break;
}
else if (err < ErrorOptimal) {
ErrorOptimal = err;
y_divide = y;
}
}
x_divide = ((uint64_t) y_divide * (audio_format->SampleRate) * 2 * (audio_format->WordWidth) * N * 2) / pClk;
if (x_divide >= 256) {
x_divide = 0xFF;
}
if (x_divide == 0) {
x_divide = 1;
}
if (audio_format->WordWidth <= 8) {
IP_I2S_SetWordWidth(pI2S, TRMode, I2S_WORDWIDTH_8);
}
else if (audio_format->WordWidth <= 16) {
IP_I2S_SetWordWidth(pI2S, TRMode, I2S_WORDWIDTH_16);
}
else {
IP_I2S_SetWordWidth(pI2S, TRMode, I2S_WORDWIDTH_32);
}
IP_I2S_SetMono(pI2S, TRMode, (audio_format->ChannelNumber) == 1 ? I2S_MONO : I2S_STEREO);
IP_I2S_SetMasterSlaveMode(pI2S, TRMode, I2S_MASTER_MODE);
IP_I2S_SetWS_Halfperiod(pI2S, TRMode, audio_format->WordWidth - 1);
IP_I2S_ModeConfig(pI2S, TRMode, I2S_TXMODE_CLKSEL(0), !I2S_TXMODE_4PIN_ENABLE, !I2S_TXMODE_MCENA);
IP_I2S_SetBitRate(pI2S, TRMode, N - 1);
IP_I2S_SetXYDivider(pI2S, TRMode, x_divide, y_divide);
return SUCCESS;
}
