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#include <stddef.h>
#include <stdint.h>
#include "uart.h"
#include "global.h"
// Loop <delay> times in a way that the compiler won't optimize away
static inline void delay(int32_t count)
{
asm volatile("__delay_%=: subs %[count], %[count], #1; bne __delay_%=\n"
: "=r"(count): [count]"0"(count) : "cc");
}
void uart_init()
{
// Disable PL011_UART.
wr32(PL011_UART_CR, 0);
// Setup the GPIO pin 14 && 15.
// Disable pull up/down for all GPIO pins & delay for 150 cycles.
wr32(GPPUD, 0);
delay(150);
// Disable pull up/down for pin 14,15 & delay for 150 cycles.
wr32(GPPUDCLK0, (1 << 14) | (1 << 15));
delay(150);
// Write 0 to GPPUDCLK0 to make it take effect.
wr32(GPPUDCLK0, 0);
// 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.
wr32(PL011_UART_IBRD, 1);
// Fractional part register = (.627 * 64) + 0.5 = 40.6 = ~40.
wr32(PL011_UART_FBRD, 40);
// Set 8 bit data transmission (1 stop bit, no parity)
// and disable FIFO to be able to receive interrupt every received
// char, not every 2 chars
wr32(PL011_UART_LCRH, (1 << 5) | (1 << 6));
// set interrupt to come when transmit FIFO becomes ≤ 1/8 full
// or receive FIFO becomes ≥ 1/8 full
// (not really matters, since we disabled FIFOs)
wr32(PL011_UART_IFLS, 0);
// Enable PL011_UART, receive & transfer part of UART.2
wr32(PL011_UART_CR, (1 << 0) | (1 << 8) | (1 << 9));
// At first, it's probably safer to disable interrupts :)
uart_irq_disable();
// The above disables the entire uart irq;
// Also disable single sources within it
wr32(PL011_UART_IMSC, 0);
}
inline static _Bool can_transmit(void)
{
return !(rd32(PL011_UART_FR) & (1 << 5));
}
inline static _Bool can_receive(void)
{
return !(rd32(PL011_UART_FR) & (1 << 4));
}
void putchar(char c)
{
while (!can_transmit());
wr32(PL011_UART_DR, c);
}
char getchar(void)
{
while (!can_receive());
return rd32(PL011_UART_DR);
}
_Bool putchar_non_blocking(char c)
{
if (can_transmit())
{
wr32(PL011_UART_DR, c);
return 0;
}
return 1;
}
int getchar_non_blocking(void)
{
if (can_receive())
return rd32(PL011_UART_DR);
return -1;
}
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