152 lines
6.1 KiB
C
152 lines
6.1 KiB
C
/* 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 USART communication (code)
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* @file usart.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 usart
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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 "usart.h" // USART header and definitions
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/** @defgroup usart USART peripheral used for UART communication
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* @{
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*/
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#define USART USART1 /**< USART peripheral */
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#define USART_RCC RCC_USART1 /**< USART peripheral clock */
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#define USART_IRQ NVIC_USART1_IRQ /**< USART peripheral interrupt signal */
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#define USART_ISR usart1_isr /**< USART interrupt service routine */
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#define USART_PORT GPIOA /**< USART port */
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#define USART_PORT_RCC RCC_GPIOA /**< USART port peripheral clock */
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#define USART_PIN_TX GPIO_USART1_TX /**< USART transmit pin (PA9) */
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#define USART_PIN_RX GPIO_USART1_RX /**< USART receive pin (PA10) */
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/** @} */
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#define USART_BAUDRATE 115200 /**< 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[USART_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[USART_BUFFER] = {0}; /**< ring buffer for data to transmit */
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static volatile uint8_t tx_i = 0; /**< current position if 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 uint8_t usart_received = 0; // same as rx_used, but since the user can write this variable we don't rely on it
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void usart_setup(void)
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{
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/* enable USART I/O peripheral */
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rcc_periph_clock_enable(USART_PORT_RCC); // enable clock for USART port peripheral
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rcc_periph_clock_enable(USART_RCC); // enable clock for USART peripheral
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gpio_set_mode(USART_PORT, GPIO_MODE_OUTPUT_10_MHZ, GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, USART_PIN_TX); // setup GPIO pin USART transmit
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gpio_set_mode(USART_PORT, GPIO_MODE_INPUT, GPIO_CNF_INPUT_PULL_UPDOWN, USART_PIN_RX); // setup GPIO pin USART receive
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gpio_set(USART_PORT, USART_PIN_RX); // pull up to avoid noise when not connected
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/* setup USART parameters */
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usart_set_baudrate(USART, USART_BAUDRATE);
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usart_set_databits(USART, 8);
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usart_set_stopbits(USART, USART_STOPBITS_1);
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usart_set_mode(USART, USART_MODE_TX_RX);
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usart_set_parity(USART, USART_PARITY_NONE);
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usart_set_flow_control(USART, USART_FLOWCONTROL_NONE);
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nvic_enable_irq(USART_IRQ); // enable the USART interrupt
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usart_enable_rx_interrupt(USART); // enable receive interrupt
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usart_enable(USART); // enable USART
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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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usart_received = 0;
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}
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void usart_putchar_blocking(char c)
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{
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usart_flush(); // empty buffer first
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usart_send_blocking(USART, c); // send character
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}
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void usart_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); // wait until transmit register is empty (transmission might not be complete)
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}
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char usart_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); // disable receive interrupt to prevent index corruption
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rx_i = (rx_i+1)%sizeof(rx_buffer); // update used buffer
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rx_used--; // update used buffer
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usart_received = rx_used; // update available data
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usart_enable_rx_interrupt(USART); // enable receive interrupt
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return to_return;
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}
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void usart_putchar_nonblocking(char c)
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{
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while (tx_used>=sizeof(tx_buffer)) { // idle until buffer has some space
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usart_enable_tx_interrupt(USART); // 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); // disable transmit interrupt to prevent index corruption
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tx_buffer[(tx_i+tx_used)%sizeof(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); // enable transmit interrupt
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}
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/** USART interrupt service routine called when data has been transmitted or received */
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void USART_ISR(void)
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{
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if (usart_get_interrupt_source(USART, 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); // disable transmit interrupt
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} else {
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usart_send(USART,tx_buffer[tx_i]); // put data in transmit register
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tx_i = (tx_i+1)%sizeof(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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if (usart_get_interrupt_source(USART, USART_SR_RXNE)) { // data has been received
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// only save data if there is space in the buffer
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if (rx_used>=sizeof(rx_buffer)) {
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usart_recv(USART); // read to clear interrupt
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} else {
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rx_buffer[(rx_i+rx_used)%sizeof(rx_buffer)] = usart_recv(USART); // put character in buffer
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rx_used++; // update used buffer
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usart_received = rx_used; // update available data
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}
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}
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}
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