/* 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 to send data using ESP8266 WiFi SoC (code)
 *  @file radio_esp8266.c
 *  @author King Kévin <kingkevin@cuvoodoo.info>
 *  @date 2016
 *  @note peripherals used: USART @ref radio_esp8266_usart
 */

/* standard libraries */
#include <stdint.h> // standard integer types
#include <stdlib.h> // general utilities
#include <string.h> // string and memory 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_esp8266.h" // radio header and definitions
#include "global.h" // common methods

/** @defgroup radio_esp8266_usart USART peripheral used for communication with radio
 *  @{
 */
#define RADIO_ESP8266_USART 2 /**< USART peripheral */
/** @} */

/* input and output buffers and used memory */
static uint8_t rx_buffer[24] = {0}; /**< buffer for received data (we only expect AT responses) */
static volatile uint16_t rx_used = 0; /**< number of byte in receive buffer */
static uint8_t tx_buffer[256] = {0}; /**< buffer for data to transmit */
static volatile uint16_t tx_used = 0; /**< number of bytes used in transmit buffer */

volatile bool radio_esp8266_activity = false;
volatile bool radio_esp8266_success = false;

void radio_esp8266_setup(void)
{
	/* enable USART I/O peripheral */
	rcc_periph_clock_enable(RCC_AFIO); // enable pin alternate function (USART)
	rcc_periph_clock_enable(USART_PORT_RCC(RADIO_ESP8266_USART)); // enable clock for USART port peripheral
	rcc_periph_clock_enable(USART_RCC(RADIO_ESP8266_USART)); // enable clock for USART peripheral
	gpio_set_mode(USART_PORT(RADIO_ESP8266_USART), GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, USART_PIN_TX(RADIO_ESP8266_USART)); // setup GPIO pin USART transmit
	gpio_set_mode(USART_PORT(RADIO_ESP8266_USART), GPIO_MODE_INPUT, GPIO_CNF_INPUT_PULL_UPDOWN, USART_PIN_RX(RADIO_ESP8266_USART)); // setup GPIO pin USART receive
	gpio_set(USART_PORT(RADIO_ESP8266_USART), USART_PIN_RX(RADIO_ESP8266_USART)); // pull up to avoid noise when not connected

	/* setup USART parameters for ESP8266 AT firmware */
	usart_set_baudrate(USART(RADIO_ESP8266_USART), 115200); // AT firmware 0.51 (SDK 1.5.0) uses 115200 bps
	usart_set_databits(USART(RADIO_ESP8266_USART), 8);
	usart_set_stopbits(USART(RADIO_ESP8266_USART), USART_STOPBITS_1);
	usart_set_mode(USART(RADIO_ESP8266_USART), USART_MODE_TX_RX);
	usart_set_parity(USART(RADIO_ESP8266_USART), USART_PARITY_NONE);
	usart_set_flow_control(USART(RADIO_ESP8266_USART), USART_FLOWCONTROL_NONE);

	nvic_enable_irq(USART_IRQ(RADIO_ESP8266_USART)); // enable the USART interrupt
	usart_enable_rx_interrupt(USART(RADIO_ESP8266_USART)); // enable receive interrupt
	usart_enable(USART(RADIO_ESP8266_USART)); // enable USART

	/* reset buffer states */
	rx_used = 0;
	tx_used = 0;
	radio_esp8266_activity = false;
	radio_esp8266_success = false;

	radio_esp8266_send((uint8_t*)"AT\r\n",4); // verify if module is present
	while (!radio_esp8266_activity || !radio_esp8266_success) { // wait for response
		__WFI(); // sleep until something happened
	}
	radio_esp8266_send((uint8_t*)"AT+RST\r\n",8); // reset module
	while (!radio_esp8266_activity || !radio_esp8266_success) { // wait for response
		__WFI(); // sleep until something happened
	}
	radio_esp8266_send((uint8_t*)"ATE0\r\n",6); // disable echoing
	while (!radio_esp8266_activity || !radio_esp8266_success) { // wait for response
		__WFI(); // sleep until something happened
	}
	while(rx_used<13 || !memmem((char*)rx_buffer, rx_used, "WIFI GOT IP\r\n", 13)) { // wait to have IP
		 __WFI(); // sleep until something happened
	}
}

void radio_esp8266_send(uint8_t* data, uint8_t length) {
	while (tx_used || !usart_get_flag(USART(RADIO_ESP8266_USART), USART_SR_TXE)) { // wait until ongoing transmission completed
		usart_enable_tx_interrupt(USART(RADIO_ESP8266_USART)); // enable transmit interrupt
		__WFI(); // sleep until something happened
	}
	usart_disable_tx_interrupt(USART(RADIO_ESP8266_USART)); // ensure transmit interrupt is disable to prevent index corruption (the ISR should already have done it)
	radio_esp8266_activity = false; // reset status because of new activity
	for (tx_used=0; tx_used<length && tx_used<LENGTH(tx_buffer); tx_used++) { // copy data
		tx_buffer[tx_used] = data[length-1-tx_used]; // put character in buffer (in reverse order)
	}
	if (tx_used) {
		usart_enable_tx_interrupt(USART(RADIO_ESP8266_USART)); // enable interrupt to send bytes
	}
}

/** USART interrupt service routine called when data has been transmitted or received */
void USART_ISR(RADIO_ESP8266_USART)(void)
{
	if (usart_get_interrupt_source(USART(RADIO_ESP8266_USART), USART_SR_TXE)) { // data has been transmitted
		if (tx_used) { // there is still data in the buffer to transmit
			usart_send(USART(RADIO_ESP8266_USART),tx_buffer[tx_used-1]); // put data in transmit register
			tx_used--; // update used size
		} else { // no data in the buffer to transmit
			usart_disable_tx_interrupt(USART(RADIO_ESP8266_USART)); // disable transmit interrupt
		}
	}
	if (usart_get_interrupt_source(USART(RADIO_ESP8266_USART), USART_SR_RXNE)) { // data has been received
		while (rx_used>=LENGTH(rx_buffer)) { // if buffer is full
			memmove(rx_buffer,&rx_buffer[1],LENGTH(rx_buffer)-1); // drop old data to make space (ring buffer are more efficient but harder to handle)
			rx_used--; // update used buffer information
		}
		rx_buffer[rx_used++] = usart_recv(USART(RADIO_ESP8266_USART)); // put character in buffer
		// if the used send a packet with these strings during the commands I'm fucked (AT commands are hard to handle perfectly)
		// ideally memmem would not be done in ISR (takes quite long)
		if (rx_used>=4 && memmem((char*)rx_buffer, rx_used, "OK\r\n", 4)) { // OK received
			radio_esp8266_activity = true; // response received
			radio_esp8266_success = true; // command succeeded
			rx_used = 0; // reset buffer
		} else if (rx_used>=7 && memmem((char*)rx_buffer, rx_used, "ERROR\r\n", 7)) { // ERROR received
			radio_esp8266_activity = true; // response received
			radio_esp8266_success = false; // command failed
			rx_used = 0; // reset buffer
		}
	}
}