spp_tx: add library to transmit over Bluetooth using UART
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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 to tje Blutooth module
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* @file
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* @author King Kévin <kingkevin@cuvoodoo.info>
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* @date 2016-2020
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* @note peripherals used: USART @ref spp_tx_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 "spp_tx.h" // own definition
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#include "global.h" // common methods
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/** @defgroup spp_tx_uart USART peripheral used for UART communication
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* @{
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*/
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#define SPP_TX_UART_ID 3 /**< USART peripheral */
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/** @} */
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#define UART_BAUDRATE 115200 /**< serial baud rate, in bits per second (with 8N1 8 bits, no parity bit, 1 stop bit settings) */
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/* output ring buffer, indexes, and available memory */
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static volatile uint8_t tx_buffer[64] = {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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void spp_tx_setup(void)
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{
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/* enable UART I/O peripheral */
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rcc_periph_clock_enable(RCC_USART_PORT(SPP_TX_UART_ID)); // enable clock for UART port peripheral
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rcc_periph_clock_enable(RCC_USART(SPP_TX_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_TX_PORT(SPP_TX_UART_ID), GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, USART_TX_PIN(SPP_TX_UART_ID)); // setup GPIO pin UART transmit
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/* setup UART parameters */
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usart_set_baudrate(USART(SPP_TX_UART_ID), UART_BAUDRATE);
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usart_set_databits(USART(SPP_TX_UART_ID), 8);
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usart_set_stopbits(USART(SPP_TX_UART_ID), USART_STOPBITS_1);
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usart_set_mode(USART(SPP_TX_UART_ID), USART_MODE_TX);
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usart_set_parity(USART(SPP_TX_UART_ID), USART_PARITY_NONE);
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usart_set_flow_control(USART(SPP_TX_UART_ID), USART_FLOWCONTROL_NONE);
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nvic_enable_irq(USART_IRQ(SPP_TX_UART_ID)); // enable the UART interrupt
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usart_enable(USART(SPP_TX_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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}
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void spp_tx_putchar_blocking(char c)
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{
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spp_tx_flush(); // empty buffer first
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usart_send_blocking(USART(SPP_TX_UART_ID), c); // send character
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}
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void spp_tx_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(SPP_TX_UART_ID)); // wait until transmit register is empty (transmission might not be complete)
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}
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void spp_tx_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(SPP_TX_UART_ID)); // enable transmit interrupt
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// don't go to sleep since this might prevent an interrupt
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}
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usart_disable_tx_interrupt(USART(SPP_TX_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(SPP_TX_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(SPP_TX_UART_ID)(void)
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{
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if (usart_get_flag(USART(SPP_TX_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(SPP_TX_UART_ID)); // disable transmit interrupt
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} else {
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usart_send(USART(SPP_TX_UART_ID),tx_buffer[tx_i]); // put data in transmit register
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tx_i = (tx_i + 1) % LENGTH(tx_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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}
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@ -0,0 +1,37 @@
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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 to tje Blutooth module
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* @file
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* @author King Kévin <kingkevin@cuvoodoo.info>
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* @date 2016-2020
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* @note peripherals used: USART @ref spp_tx_uart
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*/
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#pragma once
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/** setup UART peripheral */
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void spp_tx_setup(void);
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/** send character over UART (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 spp_tx_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 spp_tx_flush(void);
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/** send character over UART (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 spp_tx_putchar_nonblocking(char c);
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