/* 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/>.
 *
 */
/** @brief library to drive a WS2812b LED chain (code)
 *  @file led_ws2812b.c
 *  @author King Kévin <kingkevin@cuvoodoo.info>
 *  @date 2016
 *  @note peripherals used: SPI @ref led_ws2812b_spi, timer @ref led_ws2812b_timer, DMA @ref led_ws2812b_dma
 *  @todo improve ws2812b_set_rgb speed
 */

/* 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/spi.h> // SPI library
#include <libopencm3/stm32/timer.h> // timer library
#include <libopencm3/stm32/dma.h> // DMA library
#include <libopencm3/cm3/nvic.h> // interrupt handler
#include <libopencmsis/core_cm3.h> // Cortex M3 utilities

#include "led_ws2812b.h" // LED WS2812b library API
#include "global.h" // common methods

/** peripheral configuration */
/** @defgroup led_ws2812b_spi SPI peripheral used to control the WS2812b LEDs
 *  @{
 */
#define WS2812B_SPI SPI1 /**< SPI peripheral */
#define WS2812B_SPI_DR SPI1_DR /**< SPI data register for the DMA */
#define WS2812B_SPI_RCC RCC_SPI1 /**< SPI peripheral clock */
#define WS2812B_SPI_PORT GPIOA /**< SPI port */
#define WS2812B_SPI_CLK GPIO_SPI1_SCK /**< SPI clock pin (PA5), connect to PWM output */
#define WS2812B_SPI_DOUT GPIO_SPI1_MISO /**< SPI data pin (PA6), connect to WS2812b DIN */
/** @} */
/** @defgroup led_ws2812b_timer timer peripheral used to generate SPI clock
 *  @{
 */
#define WS2812B_TIMER TIM3 /**< timer peripheral */
#define WS2812B_TIMER_RCC RCC_TIM3 /**< timer peripheral clock */
#define WS2812B_TIMER_OC TIM_OC3 /**< timer output compare used to set PWM frequency */
#define WS2812B_CLK_RCC RCC_GPIOB /**< timer port peripheral clock */
#define WS2812B_CLK_PORT GPIOB /**< timer port */
#define WS2812B_CLK_PIN GPIO_TIM3_CH3 /**< timer pin to output PWM (PB0), connect to SPI clock input */
/** @} */
/** @defgroup led_ws2812b_dma DMA peripheral used to send the data
 *  @{
 */
#define WS2812B_DMA DMA1 /**< DMA peripheral to put data for WS2812b LED in SPI queue (only DMA1 supports SPI1_TX interrupt) */
#define WS2812B_DMA_RCC RCC_DMA1 /**< DMA peripheral clock */
#define WS2812B_DMA_CH DMA_CHANNEL3 /**< DMA channel (only DMA1 channel 3 supports SPI1_TX interrupt) */
#define WS2812B_DMA_IRQ NVIC_DMA1_CHANNEL3_IRQ /**< DMA channel interrupt signal */
#define WS2812B_DMA_ISR dma1_channel3_isr /**< DMA channel interrupt service routine */
/** @} */

/** @brief bit template to encode one byte to be shifted out by SPI to the WS2812b LEDs
 *  @details For each WS2812b bit which needs to be transfered we require to transfer 3 SPI bits.
 *  The first SPI bit is the high start of the WS2812b bit frame.
 *  The second SPI bit determines if the WS2812b bit is a 0 or 1.
 *  The third SPI bit is the last part of the  WS2812b bit frame, which is always low.
 *  The binary pattern is 0b100100100100100100100100
 */
#define WS2812B_SPI_TEMPLATE 0x924924

uint8_t ws2812b_data[WS2812B_LEDS*3*3+40*3/8+1] = {0};  /**< data encoded to be shifted out by SPI for the WS2812b, plus the 50us reset (~40 data bits) */
static volatile bool transmit_flag = false; /**< flag set in software when transmission started, clear by interrupt when transmission completed */

void ws2812b_set_rgb(uint16_t led, uint8_t red, uint8_t green, uint8_t blue)
{
	// verify the led exists
	if (led>=WS2812B_LEDS) {
		return;
	}
	// wait for transmission to complete before changing the color
	while (transmit_flag) {
		__WFI();
	}

	const uint8_t colors[] = {green, red, blue}; // color order for the WS2812b
	const uint8_t pattern_bit[] = {0x02, 0x10, 0x80, 0x04, 0x20, 0x01, 0x08, 0x40}; // which bit to change in the pattern
	const uint8_t pattern_byte[] = {2,2,2,1,1,0,0,0}; // in which byte in the pattern to write the pattern bit
	for (uint8_t color=0; color<LENGTH(colors); color++) { // colors are encoded similarly
		// fill the middle bit (fixed is faster than calculating it)
		for (uint8_t bit=0; bit<8; bit++) { // bit from the color to set/clear
			if (colors[color]&(1<<bit)) { // setting bit
				ws2812b_data[led*3*3+color*3+pattern_byte[bit]] |= pattern_bit[bit]; // setting bit is pattern
			} else { // clear bit
				ws2812b_data[led*3*3+color*3+pattern_byte[bit]] &= ~pattern_bit[bit]; // clearing bit is pattern
			}
		}
	}
}

void ws2812b_transmit(void)
{
	while (transmit_flag) { // wait for previous transmission to complete
		__WFI();
	}
	transmit_flag = true; // remember transmission started
	dma_set_memory_address(WS2812B_DMA, WS2812B_DMA_CH, (uint32_t)ws2812b_data);
	dma_set_number_of_data(WS2812B_DMA, WS2812B_DMA_CH, LENGTH(ws2812b_data)); // set the size of the data to transmit
	dma_enable_transfer_complete_interrupt(WS2812B_DMA, WS2812B_DMA_CH); // warm when transfer is complete to stop transmission
	dma_enable_channel(WS2812B_DMA, WS2812B_DMA_CH); // enable DMA channel

	spi_enable_tx_dma(WS2812B_SPI); // use DMA to provide data stream to be transfered

	timer_set_counter(WS2812B_TIMER, 0); // reset timer counter fro clean clock
	timer_enable_counter(WS2812B_TIMER); // start timer to generate clock
}

void ws2812b_setup(void)
{
	/* setup timer to generate clock of (using PWM): 800kHz*3 */
	rcc_periph_clock_enable(WS2812B_CLK_RCC); // enable clock for GPIO peripheral
	gpio_set_mode(WS2812B_CLK_PORT, GPIO_MODE_OUTPUT_10_MHZ, GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, WS2812B_CLK_PIN); // set pin as output
	rcc_periph_clock_enable(RCC_AFIO); // enable clock for alternate function (PWM)
	rcc_periph_clock_enable(WS2812B_TIMER_RCC); // enable clock for timer peripheral
	timer_reset(WS2812B_TIMER); // reset timer state
	timer_set_mode(WS2812B_TIMER, TIM_CR1_CKD_CK_INT, TIM_CR1_CMS_EDGE, TIM_CR1_DIR_UP); // set timer mode, use undivided timer clock, edge alignment (simple count), and count up
	timer_set_prescaler(WS2812B_TIMER, 0); // no prescaler to keep most precise timer (72MHz/2^16=1099<800kHz)
	timer_set_period(WS2812B_TIMER, rcc_ahb_frequency/800000/3-1); // set the clock frequency to 800kHz*3bit since we need to send 3 bits to output a 800kbps stream
	timer_set_oc_value(WS2812B_TIMER, WS2812B_TIMER_OC, rcc_ahb_frequency/800000/3/2); // duty cycle to 50%
	timer_set_oc_mode(WS2812B_TIMER, WS2812B_TIMER_OC, TIM_OCM_PWM1); // set timer to generate PWM (used as clock)
	timer_enable_oc_output(WS2812B_TIMER, WS2812B_TIMER_OC); // enable output to generate the clock

	/* setup SPI to transmit data (we are slave and the clock comes from the above PWM): 3 SPI bits for 1 WS2812b bit */
	rcc_periph_clock_enable(WS2812B_SPI_RCC); // enable clock for SPI peripheral
	gpio_set_mode(WS2812B_SPI_PORT, GPIO_MODE_INPUT, GPIO_CNF_INPUT_FLOAT, WS2812B_SPI_CLK); // set clock as input
	gpio_set_mode(WS2812B_SPI_PORT, GPIO_MODE_OUTPUT_10_MHZ, GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, WS2812B_SPI_DOUT); // set MISO as output
	spi_reset(WS2812B_SPI); // clear SPI values to default
	spi_set_slave_mode(WS2812B_SPI); // set SPI as slave (since we use the clock as input)
	spi_set_bidirectional_transmit_only_mode(WS2812B_SPI); // we won't receive data
	spi_set_unidirectional_mode(WS2812B_SPI); // we only need to transmit data
	spi_set_dff_8bit(WS2812B_SPI); // use 8 bits for simpler encoding (but there will be more interrupts)
	spi_set_clock_polarity_1(WS2812B_SPI); // clock is high when idle
	spi_set_clock_phase_1(WS2812B_SPI); // output data on second edge (rising)
	spi_send_msb_first(WS2812B_SPI); // send least significant bit first
	spi_enable_software_slave_management(WS2812B_SPI); // control the slave select in software (since there is no master)
	spi_set_nss_low(WS2812B_SPI); // set NSS low so we can output
	spi_enable(WS2812B_SPI); // enable SPI 
	// do not disable SPI or set NSS high since it will put MISO high, breaking the beginning of the next transmission
	
	/* configure DMA to provide the pattern to be shifted out from SPI to the WS2812b LEDs */
	rcc_periph_clock_enable(WS2812B_DMA_RCC); // enable clock for DMA peripheral
	dma_channel_reset(WS2812B_DMA, WS2812B_DMA_CH); // start with fresh channel configuration
	dma_set_memory_address(WS2812B_DMA, WS2812B_DMA_CH, (uint32_t)ws2812b_data); // set bit pattern as source address
	dma_set_peripheral_address(WS2812B_DMA, WS2812B_DMA_CH, (uint32_t)&WS2812B_SPI_DR);  // set SPI as peripheral destination address
	dma_set_read_from_memory(WS2812B_DMA, WS2812B_DMA_CH); // set direction from memory to peripheral
	dma_enable_memory_increment_mode(WS2812B_DMA, WS2812B_DMA_CH); // go through bit pattern
	dma_set_memory_size(WS2812B_DMA, WS2812B_DMA_CH, DMA_CCR_MSIZE_8BIT); // read 8 bits from memory
	dma_set_peripheral_size(WS2812B_DMA, WS2812B_DMA_CH, DMA_CCR_PSIZE_8BIT); // write 8 bits to peripheral
	dma_set_priority(WS2812B_DMA, WS2812B_DMA_CH, DMA_CCR_PL_HIGH); // set priority to high since time is crucial for the peripheral
	nvic_enable_irq(WS2812B_DMA_IRQ); // enable interrupts for this DMA channel

	// fill buffer with bit pattern
	for (uint16_t i=0; i<WS2812B_LEDS*3; i++) {
		ws2812b_data[i*3+0] = (uint8_t)(WS2812B_SPI_TEMPLATE>>16);
		ws2812b_data[i*3+1] = (uint8_t)(WS2812B_SPI_TEMPLATE>>8);
		ws2812b_data[i*3+2] = (uint8_t)(WS2812B_SPI_TEMPLATE>>0);
	}
	// fill remaining with with 0 to encode the reset code
	for (uint16_t i=WS2812B_LEDS*3*3; i<LENGTH(ws2812b_data); i++) {
		ws2812b_data[i] = 0;
	}
	ws2812b_transmit(); // set LEDs
}

/** @brief DMA interrupt service routine to stop transmission after it finished */
void WS2812B_DMA_ISR(void)
{
	if (dma_get_interrupt_flag(WS2812B_DMA, WS2812B_DMA_CH, DMA_TCIF)) { // transfer completed
		dma_clear_interrupt_flags(WS2812B_DMA, WS2812B_DMA_CH, DMA_TCIF); // clear flag
		dma_disable_transfer_complete_interrupt(WS2812B_DMA, WS2812B_DMA_CH); // stop warning transfer completed
		spi_disable_tx_dma(WS2812B_SPI); // stop SPI asking for more data
		while (SPI_SR(WS2812B_SPI) & SPI_SR_BSY); // wait for data to be shifted out
		timer_disable_counter(WS2812B_TIMER); // stop clock
		dma_disable_channel(WS2812B_DMA, WS2812B_DMA_CH); // stop using DMA
		transmit_flag = false; // transmission completed
	}	
}