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/*
* Copyright (C) 2014 Freie Universitรคt Berlin, Hinnerk van Bruinehsen
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @ingroup driver_periph
* @{
*
* @file
* @brief Low-level UART driver implementation
*
* @author Hauke Petersen <hauke.petersen@fu-berlin.de>
* @author Hinnerk van Bruinehsen <h.v.bruinehsen@fu-berlin.de>
*
*
* Support static BAUD rate calculation using UART_STDIO_BAUDRATE.
* Set UART_STDIO_BAUDRATE to the desired baud rate and pass it as a -D argument
* at compliation time (e.g. in the boards Makefile.include file).
* UART_BAUD_TOL can be set to guarantee a BAUD rate tolerance at compile time or
* to switch to double speed transmission (U2X) to achieve a lower tolerance.
* At runtime, this tolerance is not guaranteed to be met.
* However, an error message will be displayed at compile time.
*
* @}
*/
#include "cpu.h"
#include "sched.h"
#include "thread.h"
#include "periph/uart.h"
/**
* @brief Maximum percentage error in calculated baud before switching to double speed transmission (U2X)
*
* Takes whole numbers from 0 to 100, inclusive, with a default of 2.
*/
#if defined(UART_BAUD_TOL)
// BAUD_TOL is defined here as it is used by the setbaud.h utility
#define BAUD_TOL UART_BAUD_TOL
#else
#define BAUD_TOL 2
#endif
#if defined(UART_STDIO_BAUDRATE)
// BAUD and F_CPU are required by setbaud.h to calculated BRR
#define BAUD UART_STDIO_BAUDRATE
#define F_CPU CLOCK_CORECLOCK
#include <util/setbaud.h>
#endif
/**
* @brief Configured device map
* @{
*/
#if UART_NUMOF
static mega_uart_t *dev[] = {
#ifdef UART_0
UART_0,
#endif
#ifdef UART_1
UART_1,
#endif
#ifdef UART_2
UART_2,
#endif
#ifdef UART_3
UART_3
#endif
};
#else
/* fallback if no UART is defined */
static const mega_uart_t *dev[] = { NULL };
#endif
/**
* @brief Allocate memory to store the callback functions.
*/
static uart_isr_ctx_t isr_ctx[UART_NUMOF];
static void _update_brr(uart_t uart, uint16_t brr, bool double_speed)
{
dev[uart]->BRR = brr;
if (double_speed) {
dev[uart]->CSRA |= (1 << U2X0);
}
}
static void _set_brr(uart_t uart, uint32_t baudrate)
{
uint16_t brr;
#if defined(UART_STDIO_BAUDRATE)
// UBRR_VALUE and USE_2X are statically computed from <util/setbaud.h>
if (baudrate == UART_STDIO_BAUDRATE) {
_update_brr(uart, UBRR_VALUE, USE_2X);
return;
}
#endif
#if defined(UART_DOUBLE_SPEED)
brr = (CLOCK_CORECLOCK + 4UL * baudrate) / (8UL * baudrate) - 1UL;
_update_brr(uart, brr, true);
#else
brr = (CLOCK_CORECLOCK + 8UL * baudrate) / (16UL * baudrate) - 1UL;
_update_brr(uart, brr, false);
#endif
}
int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
{
/* make sure the given device is valid */
if (uart >= UART_NUMOF) {
return UART_NODEV;
}
/* register interrupt context */
isr_ctx[uart].rx_cb = rx_cb;
isr_ctx[uart].arg = arg;
/* disable and reset UART */
dev[uart]->CSRB = 0;
dev[uart]->CSRA = 0;
/* configure UART to 8N1 mode */
dev[uart]->CSRC = (1 << UCSZ00) | (1 << UCSZ01);
/* set clock divider */
_set_brr(uart, baudrate);
/* enable RX and TX and the RX interrupt */
dev[uart]->CSRB = ((1 << RXCIE0) | (1 << RXEN0) | (1 << TXEN0));
return UART_OK;
}
void uart_write(uart_t uart, const uint8_t *data, size_t len)
{
for (size_t i = 0; i < len; i++) {
while (!(dev[uart]->CSRA & (1 << UDRE0))) {};
dev[uart]->DR = data[i];
}
}
static inline void isr_handler(int num)
{
isr_ctx[num].rx_cb(isr_ctx[num].arg, dev[num]->DR);
if (sched_context_switch_request) {
thread_yield();
}
}
#ifdef UART_0_ISR
ISR(UART_0_ISR, ISR_BLOCK)
{
__enter_isr();
isr_handler(0);
__exit_isr();
}
#endif /* UART_0_ISR */
#ifdef UART_1_ISR
ISR(UART_1_ISR, ISR_BLOCK)
{
__enter_isr();
isr_handler(1);
__exit_isr();
}
#endif /* UART_1_ISR */
#ifdef UART_2_ISR
ISR(UART_2_ISR, ISR_BLOCK)
{
__enter_isr();
isr_handler(2);
__exit_isr();
}
#endif /* UART_2_ISR */
#ifdef UART_3_ISR
ISR(UART_3_ISR, ISR_BLOCK)
{
__enter_isr();
isr_handler(3);
__exit_isr();
}
#endif /* UART_3_ISR */
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