add basic LED+USART example
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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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/* Copyright (c) 2016 King Kévin <kingkevin@cuvoodoo.info> */
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/* this library handles the USART
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* it uses the TX and RX pins (depending on which USART is used)
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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 "usart.h" // USART header and definitions
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/* input and output ring buffer, indexes, and available memory */
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uint8_t rx_buffer[USART_BUFFER] = {0};
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volatile uint8_t rx_i = 0;
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volatile uint8_t rx_used = 0;
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uint8_t tx_buffer[USART_BUFFER] = {0};
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volatile uint8_t tx_i = 0;
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volatile uint8_t tx_used = 0;
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/* show the user how much data received over USART is ready */
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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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/* setup USART port */
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void usart_setup(void)
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{
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rcc_periph_clock_enable(USART_RCC); // enable USART1 clock
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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_FLOAT, USART_PIN_RX); // setup GPIO pin USART receive
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/* setup UART parameters */
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usart_set_baudrate(USART, 115200);
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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 USART2 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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/* put character on USART (blocking) */
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void usart_putchar_blocking(char c)
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{
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if (c == '\n') { // add carrier return before line feed. this is recommended for most UART terminals
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usart_putchar_blocking('\r'); // a second carrier return doesn't influence the terminal
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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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/* ensure all data has been transmitted (blocking) */
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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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__asm__("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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/* get character from USART (blocking) */
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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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__asm__("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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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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return to_return;
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}
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/* put character on USART stream (non-blocking using a buffer) */
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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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__asm__("wfi");
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}
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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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#if (USART==USART1)
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void usart1_isr(void)
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#elif (USART==USART2)
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void usart2_isr(void)
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#elif (USART==USART3)
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void usart3_isr(void)
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#endif
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{ // USART interrupt
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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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@ -0,0 +1,42 @@
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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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/* Copyright (c) 2016 King Kévin <kingkevin@cuvoodoo.info> */
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/* This library handles the USART */
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/* which USART to use */
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#define USART USART1
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#define USART_RCC RCC_USART1
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#define USART_IRQ NVIC_USART1_IRQ
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#define USART_PORT GPIOA
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#define USART_PIN_TX GPIO_USART1_TX
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#define USART_PIN_RX GPIO_USART1_RX
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/* serial baudrate, in bits per second (with 8N1 8 bits, no parity bit, 1 stop bit settings) */
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#define BAUD 115200
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/* USART RX and TX buffer sizes */
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#define USART_BUFFER 64
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/* show the user how much received is available */
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extern volatile uint8_t usart_received;
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/* setup USART port */
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void usart_setup(void);
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/* put character on USART (blocking) */
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void usart_putchar_blocking(char c);
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/* ensure all data has been transmitted (blocking) */
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void usart_flush(void);
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/* get character from USART (blocking) */
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char usart_getchar(void);
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/* put character on USART (non-blocking until buffer is full) */
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void usart_putchar_nonblocking(char c);
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@ -0,0 +1,85 @@
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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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/* Copyright (c) 2016 King Kévin <kingkevin@cuvoodoo.info> */
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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> // standard utilities
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#include <unistd.h> // standard streams
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#include <errno.h> // error number 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/cm3/scb.h> // vector table definition
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/* own libraries */
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#include "main.h" // board definitions
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#include "usart.h" // USART utilities
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/* default output (i.e. for printf) */
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int _write(int file, char *ptr, int len)
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{
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int i;
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if (file == STDOUT_FILENO || file == STDERR_FILENO) {
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for (i = 0; i < len; i++) {
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if (ptr[i] == '\n') { // add carrier return before line feed. this is recommended for most UART terminals
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usart_putchar_nonblocking('\r'); // a second line feed doesn't break the display
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}
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usart_putchar_nonblocking(ptr[i]); // send byte over USART
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}
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return i;
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}
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errno = EIO;
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return -1;
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}
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static void clock_setup(void)
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{
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rcc_clock_setup_in_hse_8mhz_out_72mhz(); // use 8 MHz high speed external clock to generate 72 MHz internal clock
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rcc_periph_clock_enable(LED_RCC); //enable clock for LED
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}
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static void gpio_setup(void)
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{
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/* set LED pin to 'output push-pull' */
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gpio_set_mode(LED_PORT, GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, LED_PIN);
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}
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int main(void)
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{
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int i, c = 0;
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SCB_VTOR = (uint32_t) 0x08002000; // relocate vector table because of the bootloader
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clock_setup();
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gpio_setup();
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usart_setup();
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setbuf(stdout, NULL); // set standard out buffer to NULL to immediately print
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setbuf(stderr, NULL); // set standard error buffer to NULL to immediately print
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/* blink the LED with every transmitted character */
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while (1) {
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gpio_toggle(LED_PORT, LED_PIN); /* LED on/off */
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printf("%c",c+'0');
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c = (c == 9) ? 0 : c + 1; /* increment c */
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for (i = 0; i < 8000000; i++) /* wait a bit */
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__asm__("nop");
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}
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return 0;
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}
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@ -0,0 +1,23 @@
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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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/* Copyright (c) 2016 King Kévin <kingkevin@cuvoodoo.info> */
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/* LED is on pin 11/PA1 */
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#define LED_PORT GPIOA
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#define LED_PIN GPIO1
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#define LED_RCC RCC_GPIOA
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/* default output (i.e. for printf) */
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int _write(int file, char *ptr, int len);
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