File content as of revision 3:36ee2aa7945a:

#include "defs.h"

#define DL_115200  52 //115200
#define DL_9600   625 //9600
#define DIV_VAL 0 //0 == do not use
#define MUL_VAL 1 //Cannot be zero

int Uart1GetC() // Returns a negative number if no character to read or if there was an error. 0 to 255 otherwise.
{
    if ((LPC_UART1->LSR & 0x01) == 0) return -1; //RDR (bit 0) is 1 if RBR has data; 0 if it is empty.
    return LPC_UART1->RBR;                       //Receive Buffer Register - oldest character in the RX FIFO
}
int Uart1PutC(char c) // Returns zero on success or -1 if the buffer was full or not ready
{
    //THRE is set immediately upon detection of an empty THR and is cleared on a THR write.
    if ((LPC_UART1->LSR & 0x20) == 0) return -1; //THRE (bit 5) is 1 if THR is empty; 0 if it is full.
    LPC_UART1->THR = c;                          //Transmit Holding Register -  newest character in the TX FIFO 
    return 0;
}

void Uart1Init(int baud)
{        
    //Enable fifos
    LPC_UART1->FCR = 1; //Bit 0 is FIFO Enable

    //Disable irqs
    LPC_UART1->IER = 0;
    
    //Enable writing to divider registers
    LPC_UART1->LCR = 0x80; //set LCR[DLAB]

    //Set divider values
    int dl = 0;
    switch (baud)
    {
        case 115200: dl = DL_115200; break;
        case   9600:
        default    : dl = DL_9600;   break;
    }
    LPC_UART1->DLM = dl >> 8;
    LPC_UART1->DLL = dl & 0xFF;
    LPC_UART1->FDR = DIV_VAL | MUL_VAL << 4;

    // 8 bit, 1 stop, no parity, disable writing to divisors; reset DLAB
    LPC_UART1->LCR = 0x03;
    
    //Select the function of the tx and rx pins: P0.15 and P0.16
    LPC_PINCON->PINSEL0  &= ~(3UL << 30);
    LPC_PINCON->PINSEL0  |=   1UL << 30; // table 80. 31:30 = 0b01; tx = P0_15;
    LPC_PINCON->PINMODE0 &= ~(3UL << 30);
    
    LPC_PINCON->PINSEL1  &= ~ 3UL;
    LPC_PINCON->PINSEL1  |=   1UL;       // table 80. 01:00 = 0b01 rx = P0_16;
    LPC_PINCON->PINMODE1 &= ~ 3UL;
}