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/* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by |
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* the Free Software Foundation, either version 3 of the License, or |
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* (at your option) any later version. |
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* |
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* This program is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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* GNU General Public License for more details. |
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* |
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* You should have received a copy of the GNU General Public License |
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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* |
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*/ |
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/** library for UART communication (code)
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* @file uart.c |
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* @author King Kévin <kingkevin@cuvoodoo.info> |
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* @date 2016 |
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* @note peripherals used: USART @ref uart |
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*/ |
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/* standard libraries */ |
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#include <stdint.h> // standard integer types |
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#include <stdio.h> // standard I/O facilities |
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#include <stdlib.h> // general utilities |
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/* STM32 (including CM3) libraries */ |
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#include <libopencm3/stm32/rcc.h> // real-time control clock library |
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#include <libopencm3/stm32/gpio.h> // general purpose input output library |
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#include <libopencm3/stm32/usart.h> // universal synchronous asynchronous receiver transmitter library |
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#include <libopencm3/cm3/nvic.h> // interrupt handler |
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#include <libopencmsis/core_cm3.h> // Cortex M3 utilities |
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#include "uart.h" // UART header and definitions |
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#include "global.h" // common methods |
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/** @defgroup uart UART peripheral used for UART communication
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* @{ |
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*/ |
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#define UART_ID 1 /**< UART peripheral */ |
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/** @} */ |
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#define UART_BAUDRATE 921600 /**< serial baudrate, in bits per second (with 8N1 8 bits, no parity bit, 1 stop bit settings) */ |
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/* input and output ring buffer, indexes, and available memory */ |
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static uint8_t rx_buffer[UART_BUFFER] = {0}; /**< ring buffer for received data */ |
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static volatile uint8_t rx_i = 0; /**< current position of read received data */ |
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static volatile uint8_t rx_used = 0; /**< how much data has been received and not red */ |
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static uint8_t tx_buffer[UART_BUFFER] = {0}; /**< ring buffer for data to transmit */ |
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static volatile uint8_t tx_i = 0; /**< current position of transmitted data */ |
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static volatile uint8_t tx_used = 0; /**< how much data needs to be transmitted */ |
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volatile bool uart_received = false; |
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void uart_setup(void) |
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{ |
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/* enable UART I/O peripheral */ |
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rcc_periph_clock_enable(USART_PORT_RCC(UART_ID)); // enable clock for UART port peripheral
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rcc_periph_clock_enable(USART_RCC(UART_ID)); // enable clock for UART peripheral
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rcc_periph_clock_enable(RCC_AFIO); // enable pin alternate function (UART)
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gpio_set_mode(USART_PORT(UART_ID), GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, USART_PIN_TX(UART_ID)); // setup GPIO pin UART transmit
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gpio_set_mode(USART_PORT(UART_ID), GPIO_MODE_INPUT, GPIO_CNF_INPUT_PULL_UPDOWN, USART_PIN_RX(UART_ID)); // setup GPIO pin UART receive
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gpio_set(USART_PORT(UART_ID), USART_PIN_RX(UART_ID)); // pull up to avoid noise when not connected
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/* setup UART parameters */ |
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usart_set_baudrate(USART(UART_ID), UART_BAUDRATE); |
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usart_set_databits(USART(UART_ID), 8); |
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usart_set_stopbits(USART(UART_ID), USART_STOPBITS_1); |
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usart_set_mode(USART(UART_ID), USART_MODE_TX_RX); |
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usart_set_parity(USART(UART_ID), USART_PARITY_NONE); |
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usart_set_flow_control(USART(UART_ID), USART_FLOWCONTROL_NONE); |
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nvic_enable_irq(USART_IRQ(UART_ID)); // enable the UART interrupt
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usart_enable_rx_interrupt(USART(UART_ID)); // enable receive interrupt
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usart_enable(USART(UART_ID)); // enable UART
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/* reset buffer states */ |
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tx_i = 0; |
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tx_used = 0; |
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rx_i = 0; |
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rx_used = 0; |
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uart_received = false; |
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} |
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void uart_putchar_blocking(char c) |
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{ |
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uart_flush(); // empty buffer first
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usart_send_blocking(USART(UART_ID), c); // send character
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} |
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void uart_flush(void) |
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{ |
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while (tx_used) { // idle until buffer is empty
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__WFI(); // sleep until interrupt
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} |
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usart_wait_send_ready(USART(UART_ID)); // wait until transmit register is empty (transmission might not be complete)
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} |
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char uart_getchar(void) |
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{ |
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while (!rx_used) { // idle until data is available
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__WFI(); // sleep until interrupt
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} |
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char to_return = rx_buffer[rx_i]; // get the next available character
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usart_disable_rx_interrupt(USART(UART_ID)); // disable receive interrupt to prevent index corruption
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rx_i = (rx_i+1)%LENGTH(rx_buffer); // update used buffer
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rx_used--; // update used buffer
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uart_received = (rx_used!=0); // update available data
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usart_enable_rx_interrupt(USART(UART_ID)); // enable receive interrupt
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return to_return; |
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} |
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void uart_putchar_nonblocking(char c) |
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{ |
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while (tx_used>=LENGTH(tx_buffer)) { // idle until buffer has some space
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usart_enable_tx_interrupt(USART(UART_ID)); // enable transmit interrupt
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__WFI(); // sleep until something happened
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} |
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usart_disable_tx_interrupt(USART(UART_ID)); // disable transmit interrupt to prevent index corruption
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tx_buffer[(tx_i+tx_used)%LENGTH(tx_buffer)] = c; // put character in buffer
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tx_used++; // update used buffer
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usart_enable_tx_interrupt(USART(UART_ID)); // enable transmit interrupt
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} |
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/** UART interrupt service routine called when data has been transmitted or received */ |
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void USART_ISR(UART_ID)(void) |
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{ |
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if (usart_get_flag(USART(UART_ID), USART_SR_TXE)) { // data has been transmitted
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if (!tx_used) { // no data in the buffer to transmit
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usart_disable_tx_interrupt(USART(UART_ID)); // disable transmit interrupt
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} else { |
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usart_send(USART(UART_ID),tx_buffer[tx_i]); // put data in transmit register
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tx_i = (tx_i+1)%LENGTH(rx_buffer); // update location on buffer
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tx_used--; // update used size
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} |
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} |
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while (usart_get_flag(USART(UART_ID), USART_SR_RXNE)) { // data has been received (repeat while receiving)
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char c = usart_recv(USART(UART_ID)); // save character and free UART buffer
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// only save data if there is space in the buffer
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if (rx_used>=LENGTH(rx_buffer)) { // if buffer is full
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rx_i = (rx_i+1)%LENGTH(rx_buffer); // drop oldest data
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rx_used--; // update used buffer information
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} |
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rx_buffer[(rx_i+rx_used)%LENGTH(rx_buffer)] = c; // put character in buffer
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rx_used++; // update used buffer
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uart_received = true; // update available data
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} |
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} |
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@ -0,0 +1,47 @@ |
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/* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by |
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* the Free Software Foundation, either version 3 of the License, or |
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* (at your option) any later version. |
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* |
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* This program is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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* GNU General Public License for more details. |
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* |
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* You should have received a copy of the GNU General Public License |
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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* |
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*/ |
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/** library for UART communication (API)
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* @file uart.h |
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* @author King Kévin <kingkevin@cuvoodoo.info> |
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* @date 2016 |
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* @note peripherals used: USART @ref uart |
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*/ |
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#pragma once |
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/** transmit and receive buffer sizes */ |
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#define UART_BUFFER 128 |
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/** how many bytes available in the received buffer since last read */ |
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extern volatile bool uart_received; |
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/** setup USART peripheral */ |
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void uart_setup(void); |
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/** send character over USART (blocking)
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* @param[in] c character to send |
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* @note blocks until character transmission started */ |
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void uart_putchar_blocking(char c); |
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/** ensure all data has been transmitted (blocking)
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* @note block until all data has been transmitted |
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*/ |
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void uart_flush(void); |
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/** get character received over USART (blocking)
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* @return character received over USART |
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* @note blocks until character is received over USART when received buffer is empty |
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*/ |
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char uart_getchar(void); |
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/** send character over USART (non-blocking)
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* @param[in] c character to send |
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* @note blocks if transmit buffer is full, else puts in buffer and returns |
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*/ |
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void uart_putchar_nonblocking(char c); |
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