/* This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */
/** library for receiving NMEA-0183 like messages over a Bluetooth module (code)
 *  @file radio_bluetooth.c
 *  @author King Kévin <kingkevin@cuvoodoo.info>
 *  @date 2017
 *  @note peripherals used: USART @ref radio_bluetooth_usart
 */
/* standard libraries */
#include <stdint.h> // standard integer types
#include <stdio.h> // standard I/O facilities
#include <stdlib.h> // general utilities
#include <string.h> // string utilities

/* STM32 (including CM3) libraries */
#include <libopencm3/stm32/rcc.h> // real-time control clock library
#include <libopencm3/stm32/gpio.h> // general purpose input output library
#include <libopencm3/stm32/usart.h> // universal synchronous asynchronous receiver transmitter library
#include <libopencm3/cm3/nvic.h> // interrupt handler
#include <libopencmsis/core_cm3.h> // Cortex M3 utilities

#include "radio_bluetooth.h" // forumslader header and definitions
#include "global.h" // common methods

/** @defgroup radio_bluetooth_usart USART peripheral used for communication with the Bluetooth module
 *  @{
 */
#define RADIO_BLUETOOTH_USART 2 /**< USART peripheral */
/** @} */

#define RADIO_BLUETOOTH_BAUDRATE 115200 /**< USART baud rate for the Bluetooth communication, in bits per second (with 8N1 8 bits, no parity bit, 1 stop bit settings) */

static volatile char rx_buffer[82] = {0}; /**< buffer for received data (82 chars is the maximum NMEA-0183 message length) */
static volatile uint8_t rx_buffer_i = 0; /**< current position of read received data */
static volatile char tx_buffer[82] = {0}; /**< buffer to transmit data */
static volatile uint8_t tx_buffer_i = 0; /**< number or remaining characters to transmit */

volatile bool radio_bluetooth_received = false;
volatile bool radio_bluetooth_transmitted = false;
volatile char radio_bluetooth_message[82+1] = {0};

void radio_bluetooth_setup(void)
{
	/* enable USART I/O peripheral */
	rcc_periph_clock_enable(USART_PORT_RCC(RADIO_BLUETOOTH_USART)); // enable clock for USART port peripheral
	rcc_periph_clock_enable(USART_RCC(RADIO_BLUETOOTH_USART)); // enable clock for USART peripheral
	rcc_periph_clock_enable(RCC_AFIO); // enable pin alternate function (USART)
	gpio_set_mode(USART_PORT(RADIO_BLUETOOTH_USART), GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, USART_PIN_TX(RADIO_BLUETOOTH_USART)); // setup GPIO pin USART transmit
	gpio_set_mode(USART_PORT(RADIO_BLUETOOTH_USART), GPIO_MODE_INPUT, GPIO_CNF_INPUT_PULL_UPDOWN, USART_PIN_RX(RADIO_BLUETOOTH_USART)); // setup GPIO pin USART receive
	gpio_set(USART_PORT(RADIO_BLUETOOTH_USART), USART_PIN_RX(RADIO_BLUETOOTH_USART)); // pull up to avoid noise when not connected

	/* setup USART parameters */
	usart_set_baudrate(USART(RADIO_BLUETOOTH_USART), RADIO_BLUETOOTH_BAUDRATE); // set baud rate
	usart_set_databits(USART(RADIO_BLUETOOTH_USART), 8); // set data bits
	usart_set_stopbits(USART(RADIO_BLUETOOTH_USART), USART_STOPBITS_1); // set stop bit
	usart_set_mode(USART(RADIO_BLUETOOTH_USART), USART_MODE_TX_RX); // enable transmit and receive
	usart_set_parity(USART(RADIO_BLUETOOTH_USART), USART_PARITY_NONE); // set parity
	usart_set_flow_control(USART(RADIO_BLUETOOTH_USART), USART_FLOWCONTROL_NONE); // set flow control

	nvic_enable_irq(USART_IRQ(RADIO_BLUETOOTH_USART)); // enable the USART interrupt
	usart_enable_rx_interrupt(USART(RADIO_BLUETOOTH_USART)); // enable receive interrupt
	usart_enable(USART(RADIO_BLUETOOTH_USART)); // enable USART

	/* reset buffer states */
	radio_bluetooth_received = false;
	rx_buffer_i = 0;
	radio_bluetooth_transmitted = false;
	tx_buffer_i = 0;
}

bool radio_bluetooth_transmit(const char* message)
{
	if (strlen(message)>LENGTH(tx_buffer)) { // message to transmit is too long
		return false;
	}
	while (tx_buffer_i) { // idle until buffer is empty
		__WFI(); // sleep until interrupt
	}
	for (uint8_t i=0; i<strlen(message); i++) { // copy message to transmit to internal buffer
		tx_buffer[strlen(message)-1-i] = message[i]; // copy in reverse orders to we can count remaining characters to transmit
	}
	tx_buffer_i = strlen(message); // save number of characters to transmit
	radio_bluetooth_transmitted = false; // reset transmit flag
	usart_enable_tx_interrupt(USART(RADIO_BLUETOOTH_USART)); // enable transmit interrupt
	return true;
}


/** USART interrupt service routine called when data has been received */
void USART_ISR(RADIO_BLUETOOTH_USART)(void)
{
	if (usart_get_flag(USART(RADIO_BLUETOOTH_USART), USART_SR_RXNE)) { // data has been received
		char c =  usart_recv(USART(RADIO_BLUETOOTH_USART)); // put character in buffer (and clear flag)
		// only save data if there is space in the buffer
		if (rx_buffer_i<LENGTH(rx_buffer)) {
			rx_buffer[rx_buffer_i++] = c;
		}
		if ('\n'==c) { // end of message received
			// verify if the message is correctly formatted
			if (rx_buffer_i<1 || '$'!=rx_buffer[0]) {
				goto malformatted;
			} else if (rx_buffer_i<2 || '\r'!=rx_buffer[rx_buffer_i-2]) {
				goto malformatted;
			}
			// copy message to user
			for (uint8_t i = 0; i < rx_buffer_i && i < LENGTH(radio_bluetooth_message); i++) {
				radio_bluetooth_message[i] = rx_buffer[i];
			}
			// terminate string
			if (rx_buffer_i<LENGTH(radio_bluetooth_message)) {
				radio_bluetooth_message[rx_buffer_i] = '\0';
			} else {
				radio_bluetooth_message[LENGTH(radio_bluetooth_message)-1]  = '\0';
			}
			radio_bluetooth_received = true; // notify user a message is available
malformatted:
			rx_buffer_i = 0; // reset buffer
		}
	}
	if (usart_get_flag(USART(RADIO_BLUETOOTH_USART), USART_SR_TXE) && tx_buffer_i) { // data has been transmitted
		usart_send(USART(RADIO_BLUETOOTH_USART),tx_buffer[--tx_buffer_i]); // put data in transmit register
		if (0==tx_buffer_i) { // no data in the buffer to transmit
			usart_disable_tx_interrupt(USART(RADIO_BLUETOOTH_USART)); // disable transmit interrupt
			radio_bluetooth_transmitted = true; // notify user
		}
	}
}