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lm4f: Add UART echo by interrupt example

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Nothing fancy, just a demonstration of the using the UART interrupt service
routine.

Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
This commit is contained in:
Alexandru Gagniuc
2013-05-08 11:39:38 -05:00
parent 1a160d794b
commit 5036510da1
3 changed files with 136 additions and 0 deletions
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93
examples/lm4f/stellaris-ek-lm4f120xl/uart_echo_interrupt/uart_echo_interrupt.c Normal file
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/*
* This file is part of the libopencm3 project.
*
* Copyright (C) 2011 Gareth McMullin <gareth@blacksphere.co.nz>
* Copyright (C) 2012 Alexandru Gagniuc <mr.nuke.me@gmail.com>
*
* This library is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this library. If not, see <http://www.gnu.org/licenses/>.
*/
#include <libopencm3/lm4f/systemcontrol.h>
#include <libopencm3/lm4f/gpio.h>
#include <libopencm3/lm4f/uart.h>
#include <libopencm3/lm4f/nvic.h>
static void uart_setup(void)
{
u32 pins;
/* Enable GPIOA in run mode. */
periph_clock_enable(RCC_GPIOA);
/* Configure PA0 and PA1 as alternate function pins */
pins = GPIO0 | GPIO1;
GPIO_AFSEL(GPIOA) |= pins;
GPIO_DEN(GPIOA) |= pins;
/* PA0 and PA1 are muxed to UART0 during power on, by default */
/* Enable the UART clock */
periph_clock_enable(RCC_UART0);
/* We need a brief delay before we can access UART config registers */
__asm__("nop");
/* Disable the UART while we mess with its setings */
uart_disable(UART0);
/* Configure the UART clock source as precision internal oscillator */
uart_clock_from_piosc(UART0);
/* Set communication parameters */
uart_set_baudrate(UART0, 921600);
uart_set_databits(UART0, 8);
uart_set_parity(UART0, UART_PARITY_NONE);
uart_set_stopbits(UART0, 1);
/* Now that we're done messing with the settings, enable the UART */
uart_enable(UART0);
}
static void uart_irq_setup(void)
{
/* Gimme and RX interrupt */
uart_enable_rx_interrupt(UART0);
/* Make sure the interrupt is routed through the NVIC */
nvic_enable_irq(NVIC_UART0_IRQ);
}
/*
* uart0_isr is declared as a weak function. When we override it here, the
* libopencm3 build system takes care that it becomes our UART0 ISR.
*/
void uart0_isr(void)
{
u8 rx;
u32 irq_clear = 0;
if (uart_is_interrupt_source(UART0, UART_INT_RX)) {
rx = uart_recv(UART0);
uart_send(UART0, rx);
irq_clear |= UART_INT_RX;
}
uart_clear_interrupt_flag(UART0, irq_clear);
}
int main(void)
{
uart_setup();
uart_irq_setup();
/*
* Not worrying about the UART here.
*/
while (1) {
/* Do some other task */
}
return 0;
}