/* 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/>.
 *
 */
/* Copyright (c) 2016 King Kévin <kingkevin@cuvoodoo.info> */
/* this library handles the communication with a HC-05 bluetooth module */
/* peripherals used: USART (check source for details) */

/* 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 "global.h" // common utilities
#include "bluetooth_hc-05.h" // USART header and definitions

/* which USART to use to talk to the bluetooth module */
#define USART USART2
#define USART_RCC RCC_USART2
#define USART_IRQ NVIC_USART2_IRQ
#define USART_PORT GPIOA
#define USART_PIN_TX GPIO_USART2_TX
#define USART_PIN_RX GPIO_USART3_RX
#define USART_BAUDRATE 9600
/* AT mode pin
 * to configure the HC-05 bluetooth module you need to put it in AT mode and use AT commands
 * there are several ways to get into AT mode, and there are several AT modes
 * - in full AT mode you can send all [defined] AT commands
 * - in mini AT mode you can't send some AT commands, such as AT+NAME
 * the AT mode is defined by the state of pin 34 of the module (top right)
 * - high: full AT mode
 * - low: mini AT mode
 * this pin is often connect to a switch on the adapter board (connected to VCC)
 * to enter AT mode:
 * - set pin 34 high when powering up, the LED will blink slowly, the baudrate will be 38400, bluetooth will be off
 * - set pin 34 high after powering up, the LED will keep blinking fast, the baudrate is user defined (AT+UART), bluetooth communication will keep working
 * setting pin 34 low after setting it high will put it into mini AT mode, except when bluetooth is not connected
 * when booting normally (fast blinking LED), the module will not respond to AT commands before setting pin 34 high
 * connect pin 34 to a STM32 GPIO to be able to go into AT mode */
#define AT_PORT GPIOB
#define AT_RCC RCC_GPIOB
#define AT_PIN GPIO5

/* input and output ring buffer, indexes, and available memory */
static uint8_t rx_buffer[BT_BUFFER] = {0};
static volatile uint8_t rx_i = 0;
static volatile uint8_t rx_used = 0;
static uint8_t tx_buffer[BT_BUFFER] = {0};
static volatile uint8_t tx_i = 0;
static volatile uint8_t tx_used = 0;
/* show the user how much data received over bluetooth is ready */
volatile uint8_t bt_received = 0; // same as rx_used, but since the user can write this variable we don't rely on it

/* display configuration of bluetooth module */
void bt_info(void)
{
	char* at_commands[] = {"AT+VERSION?","AT+ADDR?","AT+ROLE?","AT+UART?","AT+CMODE?","AT+STATE?","AT+NAME?"};
	char* ok = "OK\r\n";
	gpio_set(AT_PORT, AT_PIN); // enable AT mode
	for (uint8_t i=0; i<LENGTH(at_commands); i++) { // go through commands
		for (uint8_t j=0; j<strlen(at_commands[i]); j++) { // send command
			bt_putchar_nonblocking(at_commands[i][j]); // send character
		}
		bt_putchar_nonblocking('\r'); // send end of AT command
		bt_putchar_nonblocking('\n'); // send end of AT command
		uint8_t ok_i = 0; // how much of the ok sequence has been detected
		while (ok_i<strlen(ok)) { // print until OK has been received
			char c = bt_getchar(); // received character
			printf("%c",c); // print received character
			if (ok_i<strlen(ok) && c==ok[ok_i]) {
				ok_i++;
			} else {
				ok_i = 0;
			}
		}
		
	}
	gpio_clear(AT_PORT, AT_PIN); // disable AT mode
}

/* setup communication to bluetooth module */
void bt_setup(void)
{
	rcc_periph_clock_enable(USART_RCC); // enable USART clock
	gpio_set_mode(USART_PORT, GPIO_MODE_OUTPUT_10_MHZ, GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, USART_PIN_TX); // setup GPIO pin USART transmit
	gpio_set_mode(USART_PORT, GPIO_MODE_INPUT, GPIO_CNF_INPUT_PULL_UPDOWN, USART_PIN_RX); // setup GPIO pin USART receive
	gpio_set(USART_PORT, USART_PIN_RX); // pull up to avoid noise when not connected

	/* setup UART part */
	rcc_periph_clock_enable(USART_RCC); // enable clock for USART block
	gpio_set_mode(USART_PORT, GPIO_MODE_OUTPUT_10_MHZ, GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, USART_PIN_TX); // setup GPIO pin USART transmit
	gpio_set_mode(USART_PORT, GPIO_MODE_INPUT, GPIO_CNF_INPUT_PULL_UPDOWN, USART_PIN_RX); // setup GPIO pin USART receive
	gpio_set(USART_PORT, USART_PIN_RX); // pull up to avoid noise when not connected
	usart_set_baudrate(USART, 9600); // set baudrate
	usart_set_databits(USART, 8); // set data width (most common: 8 bits)
	usart_set_stopbits(USART, USART_STOPBITS_1); // set stop bit (most common: 1 bit)
	usart_set_parity(USART, USART_PARITY_NONE); // set parity (most common: none)	
	usart_set_mode(USART, USART_MODE_TX_RX); // enable USART to receive and transmit
	usart_set_flow_control(USART, USART_FLOWCONTROL_NONE); // no hardware flow control
    nvic_enable_irq(USART_IRQ); // enable the USART interrupt
	usart_enable_rx_interrupt(USART); // enable receive interrupt
	usart_enable(USART); // enable USART

	/* reset buffer states */
	tx_i = 0;
	tx_used = 0;
	rx_i = 0;
	rx_used = 0;
	bt_received = 0;

	/* configure AT mode pin */
	rcc_periph_clock_enable(AT_RCC); // enable clock for GPIO block
	gpio_set_mode(AT_PORT, GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, AT_PIN); // set pin to control AT mode

	/* configure HC-05 bluetooth module */
	gpio_set(AT_PORT, AT_PIN); // enable AT mode
	bool responded = false; // did the mode respond to AT command
	uint32_t baudrates[] = {115200, 38400, 9600, 57600, 19200}; // possible baudrate (order by preference)
	uint8_t baudrate_i = 0; // the detected baudrate
	for (baudrate_i = 0; baudrate_i<LENGTH(baudrates) && !responded; baudrate_i++) { // find module baudrate
		usart_set_baudrate(USART, baudrates[baudrate_i]); // set baudrate to test
		usart_send_blocking(USART, 'A'); // send AT command to test if it responded
		usart_send_blocking(USART, 'T'); // send AT command to test if it responded
		usart_send_blocking(USART, '\r'); // send AT command to test if it responded
		usart_send_blocking(USART, '\n'); // send AT command to test if it responded
		for (uint32_t i = 0; i<0xc0000; i++) { // wait 30ms for response (empiric value)
			__asm__("nop");
		}
		if ((rx_used==4 && bt_getchar()=='O' && bt_getchar()=='K' && bt_getchar()=='\r' && bt_getchar()=='\n') || (rx_used==11 && bt_getchar()=='E' && bt_getchar()=='R' && bt_getchar()=='R' && bt_getchar()=='O' && bt_getchar()=='R' &&  bt_getchar()==':' && bt_getchar()=='(' && bt_getchar()=='0' && bt_getchar()==')' && bt_getchar()=='\r' && bt_getchar()=='\n')) {
			responded = true; // seems we found the right baudrate since it responded
		}
		// reset buffer states
		rx_i = 0;
		rx_used = 0;
	}
	gpio_clear(AT_PORT, AT_PIN); // disable AT mode
	if (responded) {
		printf("baudrate: %lubps\n",baudrates[--baudrate_i]);
		gpio_clear(AT_PORT, AT_PIN);
	} else {
		printf("couldn't find baudrate\n");
	}
	//usart_set_baudrate(USART, USART_BAUDRATE); // set final baudrate

	bt_info();

}

/* send character over bluetooth (blocking) */
void bt_putchar_blocking(char c)
{
	bt_flush(); // empty buffer first
	usart_send_blocking(USART, c); // send character
}

/* ensure all data has been transmitted (blocking) */
void bt_flush(void)
{
	while (tx_used) { // idle until buffer is empty
		__WFI(); // sleep until interrupt
	}
	usart_wait_send_ready(USART); // wait until transmit register is empty (transmission might not be complete)
}

/* get character received over bluetooth (blocking) */
char bt_getchar(void)
{
	while (!rx_used) { // idle until data is available
		__WFI(); // sleep until interrupt;
	}
	char to_return = rx_buffer[rx_i]; // get the next available character
	rx_i = (rx_i+1)%sizeof(rx_buffer); // update used buffer
	rx_used--; // update used buffer
	bt_received = rx_used; // update available data
	return to_return;
}

/* send character over bluetooth (non-blocking until buffer is full) */
void bt_putchar_nonblocking(char c)
{
	while (tx_used>=sizeof(tx_buffer)) { // idle until buffer has some space
		usart_enable_tx_interrupt(USART); // enable transmit interrupt
		__WFI(); // sleep until something happened
	}
	tx_buffer[(tx_i+tx_used)%sizeof(tx_buffer)] = c; // put character in buffer
	tx_used++; // update used buffer
	usart_enable_tx_interrupt(USART); // enable transmit interrupt
}

#if (USART==USART1)
void usart1_isr(void)
#elif (USART==USART2)
void usart2_isr(void)
#elif (USART==USART3)
void usart3_isr(void)
#endif
{ // USART interrupt
	if (usart_get_interrupt_source(USART, USART_SR_TXE)) { // data has been transmitted
		if (!tx_used) { // no data in the buffer to transmit
			usart_disable_tx_interrupt(USART); // disable transmit interrupt
		} else {
			usart_send(USART,tx_buffer[tx_i]); // put data in transmit register
			tx_i = (tx_i+1)%sizeof(rx_buffer); // update location on buffer
			tx_used--; // update used size
		}
	}
	if (usart_get_interrupt_source(USART, USART_SR_RXNE)) { // data has been received
		// only save data if there is space in the buffer
		if (rx_used>=sizeof(rx_buffer)) {
			usart_recv(USART); // read to clear interrupt
		} else {
			rx_buffer[(rx_i+rx_used)%sizeof(rx_buffer)] = usart_recv(USART); // put character in buffer
			rx_used++; // update used buffer
			bt_received = rx_used; // update available data
		}
	}
}