Baud rate setting for UART in LPC1788

Question

I am working with UART of lPC1788,in that I did the following settings for PCLK as 12MHZ and baud rate as 115200 but while I am simulating this code the baud rate is not assigned as 115200 or approx.

uint32_t uart0_init()
{

  LPC_SC->PCONP |=(1<<3);        //Enabling power/clock for UART0
  LPC_IOCON->P0_2 = 1;           //Selecting fn. 001 for P0.2(U0_TXD)
  LPC_IOCON->P0_3 = 1;           //Selecting fn. 001 for P0.3(U0_RXD)
  LPC_UART0->LCR =(0x83);        //Selecting DLAB=1,1 stop bit,Parity bit and 8-bit character length

  LPC_UART0->DLL = 0x04;         //For PCLK=12MHZ and baud rate as 115200,DLL=4(in dec.)
  LPC_UART0->DLM = 0x00;         //For PCLK=12MHZ and baud rate as 115200,DLM=0(in dec.)
  LPC_UART0->FDR =(0x85);        //DIVADDVAL=1(3:0) and MULVAL=2(7:4) in FDR calculated from the FRest value 
  LPC_UART0->LCR =(0x03);        //Disabling DLAB=0
  LPC_UART0->FCR |=(7<<0);       //Enable FIFOEN,TXFIFORES and RXFIFORES in FCR(0,1,2)

  LPC_UART0->FCR |=(0<<0);       //Disable FIFOEN,TXFIFORES and RXFIFORES in FCR(0,1,2)

  //NVIC_EnableIRQ(UART0_IRQn);

  //LPC_UART0->IER = IER_RBRIE | IER_THREIE | IER_RXIE;

  return 1;

}

For me its coming near 384615,its totally different.Is there any calculations to be done to obtain exact of 115200 baud.

Please do clear for me..

Did you change PLLClock ? PCLKSEL is 12Mhz ? whats the CCLKSEL ? — Gossamer
Its 120Mhz and default PCLKSEL value is 0x02,so the obtained PCLK value in the clock divider window during simulation is 60mhz. So whether I can add LPC_SC->PCLKSEL |=(1<<3); — Vignesh_Jay

Gossamer Gossamer · Accepted Answer · 2013-06-06T12:44:25

Dont use uart init to change system control settings. You will overwrite them elsewhere if you are not careful. Create sysInit function and set it there. Set divider to 10 (0x0a).

LPC_SC->PCLKSEL = 0x0A;

This will divide MCLK with 10 and you will get 12Mhz clock for peripherals. After that you need to set FDR and DLL settings to achieve ~115200 baud.

Baud rate setting for UART in LPC1788

1 Answers