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#include <stddef.h>
#include <stdint.h>
#include "uart.h"
#include "global.h"
void uart_init(uint32_t baud, uint32_t config)
{
// PL011 UART must be disabled before configuring
wr32(PL011_UART_CR, 0);
// GPIO pins used for UART should have pull up/down disabled
// Procedure as described in BCM2835 ARM Peripherals
wr32(GPPUD, 0);
for (int i = 0; i < 150; i++) // delay for at least 150 cycles
asm volatile("nop");
wr32(GPPUDCLK0, (1 << 14) | (1 << 15));
for (int i = 0; i < 150; i++)
asm volatile("nop");
wr32(GPPUDCLK0, 0);
wr32(GPPUD, 0);
// Setting clock rate
// As described in UART (PL011) Technical Reference Manual
uint32_t int_part = DEFAULT_UART_CLOCK_RATE / (16 * baud);
uint32_t rest = DEFAULT_UART_CLOCK_RATE % (16 * baud);
uint32_t fract_part = (rest * 64 * 2 + 1) / (2 * 16 * baud);
wr32(PL011_UART_IBRD, int_part);
wr32(PL011_UART_FBRD, fract_part);
// Set data transmission specified by caller
// Don't enable FIFO to be able to receive interrupt every received
// char, not every 2 chars
wr32(PL011_UART_LCRH, config);
// 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 UART receiving and transmitting, as well as UART itself
wr32(PL011_UART_CR, (1 << 9) | (1 << 8) | 1);
// 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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