/* 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 query measurements from peacefair PZEM-004 and PZEM-004T electricity meter (code)
 *  @file sensor_pzem.c
 *  @author King Kévin <kingkevin@cuvoodoo.info>
 *  @date 2016
 *  @note peripherals used: USART @ref sensor_pzem_usart
 */

/* standard libraries */
#include <stdint.h> // standard integer types
#include <stdlib.h> // general 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 "sensor_pzem.h" // PZEM electricity meter header and definitions
#include "global.h" // common methods

/** @defgroup sensor_pzem_usart USART peripheral used for communication with electricity meter
 *  @{
 */
#define SENSOR_PZEM_USART 2 /**< USART peripheral */
/** @} */

/* input and output ring buffer, indexes, and available memory */
static uint8_t rx_buffer[7] = {0}; /**< buffer for received response */
static volatile uint8_t rx_i = 0; /**< current position of read received data */
static uint8_t tx_buffer[7] = {0}; /**< buffer for request to transmit */
static volatile uint8_t tx_i = 0; /**< current position of transmitted data */

volatile bool sensor_pzem_measurement_received = false;

void sensor_pzem_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(SENSOR_PZEM_USART)); // enable clock for USART port peripheral
	rcc_periph_clock_enable(USART_RCC(SENSOR_PZEM_USART)); // enable clock for USART peripheral
	gpio_set_mode(USART_PORT(SENSOR_PZEM_USART), GPIO_MODE_OUTPUT_2_MHZ, GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, USART_PIN_TX(SENSOR_PZEM_USART)); // setup GPIO pin USART transmit
	gpio_set_mode(USART_PORT(SENSOR_PZEM_USART), GPIO_MODE_INPUT, GPIO_CNF_INPUT_PULL_UPDOWN, USART_PIN_RX(SENSOR_PZEM_USART)); // setup GPIO pin USART receive
	gpio_set(USART_PORT(SENSOR_PZEM_USART), USART_PIN_RX(SENSOR_PZEM_USART)); // pull up to avoid noise when not connected

	/* setup USART parameters for electricity meter: 9600 8N1 */
	usart_set_baudrate(USART(SENSOR_PZEM_USART), 9600); // the electricity meter uses a fixed baud rate of 9600 bps
	usart_set_databits(USART(SENSOR_PZEM_USART), 8);
	usart_set_stopbits(USART(SENSOR_PZEM_USART), USART_STOPBITS_1);
	usart_set_mode(USART(SENSOR_PZEM_USART), USART_MODE_TX_RX);
	usart_set_parity(USART(SENSOR_PZEM_USART), USART_PARITY_NONE);
	usart_set_flow_control(USART(SENSOR_PZEM_USART), USART_FLOWCONTROL_NONE);

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

	/* reset buffer states */
	tx_i = 0;
	rx_i = 0;
	sensor_pzem_measurement_received = false;
}

void sensor_pzem_measurement_request(uint32_t address, enum sensor_pzem_measurement_type_t type)
{
	if (tx_i!=0) { // transmission is ongoing
		return;
	}
	if (type>=SENSOR_PZEM_MAX) { // invalid type
		return;
	}
	tx_buffer[0] = 0xB0+type; // set request nibble and type nibble
	tx_buffer[1] = (address>>24)&0xff; // set address
	tx_buffer[2] = (address>>16)&0xff; // set address
	tx_buffer[3] = (address>>8)&0xff; // set address
	tx_buffer[4] = (address>>0)&0xff; // set address
	tx_buffer[5] = 0; // only used to set alarm
	tx_buffer[6] = 0; // to calculate checksum (sum of all previous bytes)
	for (uint8_t i=0; i<LENGTH(tx_buffer)-1; i++) {
		tx_buffer[6] += tx_buffer[i]; // calculate buffer
	}

	usart_enable_tx_interrupt(USART(SENSOR_PZEM_USART)); // enable interrupt to send other bytes
	usart_send(USART(SENSOR_PZEM_USART),tx_buffer[tx_i++]); // start transmission
}

struct sensor_pzem_measurement_t sensor_pzem_measurement_decode(void)
{
	struct sensor_pzem_measurement_t measurement; // decoded measurement to return
	measurement.valid = false; // wait until the end to ensure validity
	if (!sensor_pzem_measurement_received) { // no measurement received
		return measurement;
	}
	if ((rx_buffer[0]&0xf0)!=0xa0) { // not a response received
		return measurement;
	}
	if ((rx_buffer[0]&0x0f)>=SENSOR_PZEM_MAX) { // not a valid response type received (actually 4 and 5 are valid, but should not happen when using this code
		return measurement;
	}
	uint8_t checksum = 0; // calculate checksum (sum of all other bytes)
	for (uint8_t i=0; i<LENGTH(rx_buffer)-1; i++) {
		checksum += rx_buffer[i]; // calculate buffer
	}
	if (checksum!=rx_buffer[6]) { // checksum does not match
		return measurement;
	}
	measurement.valid = true; // all checks passed
	measurement.type = rx_buffer[0]&0x0f; // save type
	switch (measurement.type) { // decode value depending on type
		case SENSOR_PZEM_VOLTAGE:
			measurement.value.voltage = ((uint16_t)rx_buffer[1]<<8)+rx_buffer[2]+rx_buffer[3]*0.1;
			break;
		case SENSOR_PZEM_CURRENT:
			measurement.value.current = rx_buffer[2]+rx_buffer[3]/100;
			break;
		case SENSOR_PZEM_POWER:
			measurement.value.power = ((uint16_t)rx_buffer[1]<<8)+rx_buffer[2];
			break;
		case SENSOR_PZEM_ENERGY:
			measurement.value.energy = ((uint32_t)rx_buffer[1]<<16)+((uint16_t)rx_buffer[2]<<8)+rx_buffer[3];
			break;
/* not used in this application
		case SENSOR_PZEM_ADDRESS:
		case SENSOR_PZEM_ALARM:
			break; // no value is returned
*/
		default:
			measurement.valid = false; // unexpected type
	}
	sensor_pzem_measurement_received = false; // reset flag
	rx_i = 0; // prepare buffer to receive next measurement
	return measurement;
}
	
/** USART interrupt service routine called when data has been transmitted or received */
void USART_ISR(SENSOR_PZEM_USART)(void)
{
	if (usart_get_interrupt_source(USART(SENSOR_PZEM_USART), USART_SR_TXE)) { // data has been transmitted
		if (tx_i<LENGTH(tx_buffer)) { // not all bytes transmitted
			usart_send(USART(SENSOR_PZEM_USART),tx_buffer[tx_i++]); // transmit next byte
		} else { // request transmitted
			usart_disable_tx_interrupt(USART(SENSOR_PZEM_USART)); // disable transmit interrupt
			tx_i = 0; // ready for next transmission
		}
	}
	if (usart_get_interrupt_source(USART(SENSOR_PZEM_USART), USART_SR_RXNE)) { // data has been received
		if (rx_i<LENGTH(rx_buffer)) { // receiving response
			rx_buffer[rx_i++] = usart_recv(USART(SENSOR_PZEM_USART)); // put received byte in buffer
			if (rx_i>=LENGTH(rx_buffer)) { // buffer full
				sensor_pzem_measurement_received = true; // notify used response has been received
			}
		} else { // previous response not read before receiving the next
			usart_recv(USART(SENSOR_PZEM_USART)); // drop received buffer
		}
	}
}