Beispiel #1
0
/* Determines and sets best dividers to get a target baud rate */
uint32_t Chip_UART_SetBaudFDR(LPC_USART_T *pUART, uint32_t baudrate)

{
	uint32_t uClk;
	uint32_t dval, mval;
	uint32_t dl;
	uint32_t rate16 = 16 * baudrate;
	uint32_t actualRate = 0;

	/* Get Clock rate */
	uClk = Chip_Clock_GetMainClockRate();

	/* The fractional is calculated as (PCLK  % (16 * Baudrate)) / (16 * Baudrate)
	 * Let's make it to be the ratio DivVal / MulVal
	 */
	dval = uClk % rate16;

	// NOTE: added initialization. Otherwise value may be used without initialization.
	mval = 0;

	/* The PCLK / (16 * Baudrate) is fractional
	 * => dval = pclk % rate16
	 * mval = rate16;
	 * now mormalize the ratio
	 * dval / mval = 1 / new_mval
	 * new_mval = mval / dval
	 * new_dval = 1
	 */
	if (dval > 0) {
		mval = rate16 / dval;
		dval = 1;

		/* In case mval still bigger then 4 bits
		 * no adjustment require
		 */
		if (mval > 12) {
			dval = 0;
		}
	}
	dval &= 0xf;
	// TODO: mval may be non initialized.
	mval &= 0xf;
	dl = uClk / (rate16 + rate16 * dval / mval);

	/* Update UART registers */
	Chip_UART_EnableDivisorAccess(pUART);
	Chip_UART_SetDivisorLatches(pUART, UART_LOAD_DLL(dl), UART_LOAD_DLM(dl));
	Chip_UART_DisableDivisorAccess(pUART);

	/* Set best fractional divider */
	pUART->FDR = (UART_FDR_MULVAL(mval) | UART_FDR_DIVADDVAL(dval));

	/* Return actual baud rate */
	actualRate = uClk / (16 * dl + 16 * dl * dval / mval);
	return actualRate;
}
Beispiel #2
0
/* Determines and sets best dividers to get a target bit rate */
uint32_t Chip_UART_SetBaud(LPC_USART_T *pUART, uint32_t baudrate)
{
	uint32_t div, divh, divl, clkin;

	/* Determine UART clock in rate without FDR */
	clkin = Chip_Clock_GetMainClockRate();
	div = clkin / (baudrate * 16);

	/* High and low halves of the divider */
	divh = div / 256;
	divl = div - (divh * 256);

	Chip_UART_EnableDivisorAccess(pUART);
	Chip_UART_SetDivisorLatches(pUART, divl, divh);
	Chip_UART_DisableDivisorAccess(pUART);

	/* Fractional FDR alreadt setup for 1 in UART init */

	return clkin / div;
}