uart.c

#include "mmio.h"
#include "uart.h"
#include "sys.h"

void uart_init() {
    // Disable UART.
    mmio_write(UART_CR, 0x00000000);
    // Setup the GPIO pin 14 && 15.
 
    // Disable pull up/down for all GPIO pins & delay for 150 cycles.
    mmio_write(GPPUD, 0x00000000);
    delay(150);
 
    // Disable pull up/down for pin 14,15 & delay for 150 cycles.
    mmio_write(GPPUDCLK0, (1 << 14) | (1 << 15));
    delay(150);
 
    // Write 0 to GPPUDCLK0 to make it take effect.
    mmio_write(GPPUDCLK0, 0x00000000);
 
    // Clear pending interrupts.
    mmio_write(UART_ICR, 0x7FF);
 
    // Set integer & fractional part of baud rate.
    // Divider = UART_CLOCK/(16 * Baud)
    // Fraction part register = (Fractional part * 64) + 0.5
    // UART_CLOCK = 3000000; Baud = 115200.
 
    // Divider = 3000000/(16 * 115200) = 1.627 = ~1.
    // Fractional part register = (.627 * 64) + 0.5 = 40.6 = ~40.
    mmio_write(UART_IBRD, 1);
    mmio_write(UART_FBRD, 40);
 
    // Enable FIFO & 8 bit data transmissio (1 stop bit, no parity).
    mmio_write(UART_LCRH, (1 << 4) | (1 << 5) | (1 << 6));
 
    // Mask all interrupts.
    mmio_write(UART_IMSC, (1 << 1) | (1 << 4) | (1 << 5) |
		    (1 << 6) | (1 << 7) | (1 << 8) |
		    (1 << 9) | (1 << 10));
 
    // Enable UART, receive & transfer part of UART.
    mmio_write(UART_CR, (1 << 0) | (1 << 8) | (1 << 9));
}

void uart_putc(uint8_t byte) {
        while ((mmio_read(UART_FR) & (1 << 5)));
        mmio_write(UART_DR, byte);
}

void uart_puts(char *bytes) {
        while(*bytes) uart_putc(*(bytes++));
}

uint8_t uart_getc() {
        while(mmio_read(UART_FR) & 0x10);
        return mmio_read(UART_DR);
}