// See fsl_lpuart_hal.h for documentation of this function.
status_t lpuart_hal_set_baud_rate(LPUART_Type * baseAddr, uint32_t sourceClockInHz,
uint32_t desiredBaudRate)
{
// Calculate SBR rounded to nearest whole number, 14.4 = 14, 14.6 = 15
// This gives the least error possible
uint32_t sbr = (uint32_t)(((sourceClockInHz * 10)/(desiredBaudRate * kLPUART_OSR_Value)) + 5) / 10;
uint32_t calculatedBaud = (uint32_t)(sourceClockInHz/(sbr * kLPUART_OSR_Value));
uint32_t baudDiff = MAX(calculatedBaud, desiredBaudRate) - MIN(calculatedBaud, desiredBaudRate);
// next, check to see if actual baud rate is within 3% of desired baud rate
// based on the best calculate osr value
if (baudDiff < ((desiredBaudRate / 100) * 3))
{
// program the osr value (bit value is one less than actual value)
LPUART_WR_BAUD(baseAddr,
LPUART_BAUD_OSR(kLPUART_OSR_Value - 1) |
LPUART_BAUD_SBR(sbr) |
LPUART_BAUD_BOTHEDGE_MASK);
}
else
{
// Unacceptable baud rate difference of more than 3%
return kStatus_LPUART_BaudRatePercentDiffExceeded;
}
return kStatus_Success;
}
/*
* Initialises the LPUART
*
* @param baudrate - the baud rate to use e.g. 19200
*/
void uart_initialise(int baudrate) {
initDefaultUart();
#define OVERSAMPLE (16)
// Disable LPUART before changing registers
LPUART->CTRL &= ~(LPUART_CTRL_RE_MASK|LPUART_CTRL_TE_MASK);
// Calculate LPUART clock setting
int baudValue = UART_CLOCK/(OVERSAMPLE*baudrate);
// Set Baud rate register
LPUART->BAUD = LPUART_BAUD_SBR(baudValue)|LPUART_BAUD_OSR(OVERSAMPLE-1);
#ifdef USE_IRQ
// Enable LPUART Tx & Rx - with Rx IRQ
LPUART->CTRL = LPUART_CTRL_RE_MASK|LPUART_CTRL_TE_MASK|LPUART_CTRL_RIE_MASK|LPUART_CTRL_TIE_MASK;
#else
// Enable LPUART Tx & Rx
LPUART->CTRL = LPUART_CTRL_RE_MASK|LPUART_CTRL_TE_MASK;
#endif
}