/** library to communicate using microwore as master
 *  @file
 *  @author King Kévin <kingkevin@cuvoodoo.info>
 *  @copyright SPDX-License-Identifier: GPL-3.0-or-later
 *  @date 2017-2020
 *  @note peripherals used: GPIO @ref microwire_master_gpio, timer @ref microwire_master_timer
 *  microwire is a 3-Wire half-duplex synchronous bus. It is very similar to SPI without fixed length messages (bit-wised).
 *  @note the user has to handle the slave select pin (high during operations) so to be able to handle multiple slaves.
 *  @warning this library implements the M93Cx8 EEPROM operation codes. Other microwire-based ICs might use different ones.
 */

/* standard libraries */
#include <stdint.h> // standard integer types
#include <stdlib.h> // general utilities

/* STM32 (including CM3) libraries */
#include <libopencmsis/core_cm3.h> // Cortex M3 utilities
#include <libopencm3/stm32/rcc.h> // real-time control clock library
#include <libopencm3/stm32/gpio.h> // general purpose input output library
#include <libopencm3/stm32/timer.h> // timer utilities

#include "global.h" // global utilities
#include "microwire_master.h" // microwire header and definitions

/** @defgroup microwire_master_gpio GPIO peripheral used to communicate
 *  @{
 */
#define MICROWIRE_MASTER_SDO_PIN PA0 /**< SDO output signal pin (to be connected on D slave signal) */
#define MICROWIRE_MASTER_SDI_PIN PA2 /**< SDO input signal pin (to be connected on Q slave signal) */
#define MICROWIRE_MASTER_SCK_PIN PA4 /**< SCK output signal pin (to be connected on C slave signal) */
/** @} */

/** @defgroup microwire_master_timer timer peripheral used to generate timing for the signal
 *  @{
 */
#define MICROWIRE_MASTER_TIMER 4 /**< timer peripheral */
/** @} */

/** address size used in operations (slave specific) */
uint8_t mirowire_master_address_size = 0;
/** organization used (true=x16, false=x8) */
bool mirowire_master_organization_x16 = true;

void microwire_master_setup(uint32_t frequency, bool organization_x16, uint8_t address_size)
{
	// sanity checks
	if (0 == frequency || 0 == address_size) {
		return;
	}
	mirowire_master_address_size = address_size; // save address size
	mirowire_master_organization_x16 = organization_x16; // save organisation

	// setup GPIO
	rcc_periph_clock_enable(GPIO_RCC(MICROWIRE_MASTER_SDO_PIN)); // enable clock for GPIO domain for SDO signal
	gpio_set_mode(GPIO_PORT(MICROWIRE_MASTER_SDO_PIN), GPIO_MODE_OUTPUT_10_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO_PIN(MICROWIRE_MASTER_SDO_PIN)); // set SDO signal as output (controlled by the master)
	gpio_clear(GPIO_PORT(MICROWIRE_MASTER_SDO_PIN), GPIO_PIN(MICROWIRE_MASTER_SDO_PIN)); // SDO is idle low
	rcc_periph_clock_enable(GPIO_RCC(MICROWIRE_MASTER_SDI_PIN)); // enable clock for GPIO domain for SDI signal
	gpio_set_mode(GPIO_PORT(MICROWIRE_MASTER_SDI_PIN), GPIO_MODE_INPUT, GPIO_CNF_INPUT_FLOAT, GPIO_PIN(MICROWIRE_MASTER_SDI_PIN)); // set SDI signal as output (controlled by the slave)
	rcc_periph_clock_enable(GPIO_RCC(MICROWIRE_MASTER_SCK_PIN)); // enable clock for GPIO domain for SCK signal
	gpio_set_mode(GPIO_PORT(MICROWIRE_MASTER_SCK_PIN), GPIO_MODE_OUTPUT_10_MHZ, GPIO_CNF_OUTPUT_PUSHPULL, GPIO_PIN(MICROWIRE_MASTER_SCK_PIN)); // set SCK signal as output (controlled by the master)
	gpio_clear(GPIO_PORT(MICROWIRE_MASTER_SCK_PIN), GPIO_PIN(MICROWIRE_MASTER_SCK_PIN)); // SCK is idle low

	// setup timer to generate timing for the signal
	rcc_periph_clock_enable(RCC_TIM(MICROWIRE_MASTER_TIMER)); // enable clock for timer domain
	rcc_periph_reset_pulse(RST_TIM(MICROWIRE_MASTER_TIMER)); // reset timer state
	timer_set_mode(TIM(MICROWIRE_MASTER_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
	uint16_t prescaler = rcc_ahb_frequency / (frequency * 2) / (uint32_t)(1 << 16) + 1; // calculate prescaler for most accurate timing for this speed
	timer_set_prescaler(TIM(MICROWIRE_MASTER_TIMER), prescaler - 1); // set calculated prescaler
	uint16_t period = (rcc_ahb_frequency / prescaler) / (frequency * 2); // calculate period to get most accurate timing based on the calculated prescaler
	timer_set_period(TIM(MICROWIRE_MASTER_TIMER), period - 1); // set calculated period
	timer_update_on_overflow(TIM(MICROWIRE_MASTER_TIMER)); // only use counter overflow as UEV source (use overflow as timeout)
	SCB_SCR |= SCB_SCR_SEVONPEND; // enable wake up on event (instead of using ISR)
	timer_enable_irq(TIM(MICROWIRE_MASTER_TIMER), TIM_DIER_UIE); // enable update interrupt for timer
}

/** wait for clock tick used to synchronise communication */
static void microwire_master_wait_clock(void)
{
		while ( !timer_get_flag(TIM(MICROWIRE_MASTER_TIMER), TIM_SR_UIF)) { // wait for timer overflow event for clock change
			__asm__("wfe"); // go to sleep and wait for event
		}
		timer_clear_flag(TIM(MICROWIRE_MASTER_TIMER), TIM_SR_UIF); // clear timer flag
		nvic_clear_pending_irq(NVIC_TIM_IRQ(MICROWIRE_MASTER_TIMER)); // clear IRQ flag (else event doesn't wake up)
}

/** send bit over microwire
 *  @param[in] bit bit to send (true = '1', false = '0')
 */
static void microwire_master_send_bit(bool bit)
{
	if (bit) {
		gpio_set(GPIO_PORT(MICROWIRE_MASTER_SDO_PIN), GPIO_PIN(MICROWIRE_MASTER_SDO_PIN)); // set '1' on output
	} else {
		gpio_clear(GPIO_PORT(MICROWIRE_MASTER_SDO_PIN), GPIO_PIN(MICROWIRE_MASTER_SDO_PIN)); // set '0' on output
	}
	microwire_master_wait_clock(); // wait for clock timing
	gpio_set(GPIO_PORT(MICROWIRE_MASTER_SCK_PIN), GPIO_PIN(MICROWIRE_MASTER_SCK_PIN)); // make rising edge for slave to sample
	microwire_master_wait_clock(); // keep output signal stable while clock is high
	gpio_clear(GPIO_PORT(MICROWIRE_MASTER_SCK_PIN), GPIO_PIN(MICROWIRE_MASTER_SCK_PIN)); // put clock back to idle
}

/** initialize microwire communication and send header (with leading start bit '1')
 *  @param[in] operation operation code to send (2 bits)
 *  @param[in] address slave memory address to select
 */
static void microwire_master_start(uint8_t operation, uint32_t address)
{
	// to sanity checks
	if (0==mirowire_master_address_size) { // can't send address
		return;
	}

	// initial setup
	gpio_clear(GPIO_PORT(MICROWIRE_MASTER_SCK_PIN), GPIO_PIN(MICROWIRE_MASTER_SCK_PIN)); // ensure clock is low (to sample on rising edge)
	timer_set_counter(TIM(MICROWIRE_MASTER_TIMER), 0); // reset timer counter
	timer_clear_flag(TIM(MICROWIRE_MASTER_TIMER), TIM_SR_UIF); // clear timer flag
	nvic_clear_pending_irq(NVIC_TIM_IRQ(MICROWIRE_MASTER_TIMER)); // clear IRQ flag (else event doesn't wake up)
	timer_enable_counter(TIM(MICROWIRE_MASTER_TIMER)); // start timer to generate timing

	// send '1' start bit
	microwire_master_send_bit(true); // send start bit
	// send two bits operation code
	if (operation & 0x2) { // send first bit (MSb first)
		microwire_master_send_bit(true); // send '1'
	} else {
		microwire_master_send_bit(false); // send '2'
	}
	if (operation & 0x1) { // send second bit (LSb last)
		microwire_master_send_bit(true); // send '1'
	} else {
		microwire_master_send_bit(false); // send '2'
	}

	// send address
	for (uint8_t bit = mirowire_master_address_size; bit > 0; bit--) {
		if ((address >> (bit - 1)) & 0x01) {
			microwire_master_send_bit(true); // send '1' address bit
		} else {
			microwire_master_send_bit(false); // send '0' address bit
		}
	}
	gpio_clear(GPIO_PORT(MICROWIRE_MASTER_SDO_PIN), GPIO_PIN(MICROWIRE_MASTER_SDO_PIN)); // ensure output is idle low (could be floating)
}

/** stop microwire communication and end all activities */
static void microwire_master_stop(void)
{
	timer_disable_counter(TIM(MICROWIRE_MASTER_TIMER)); // disable timer
	timer_set_counter(TIM(MICROWIRE_MASTER_TIMER), 0); // reset timer counter
	timer_clear_flag(TIM(MICROWIRE_MASTER_TIMER), TIM_SR_UIF); // clear timer flag
	nvic_clear_pending_irq(NVIC_TIM_IRQ(MICROWIRE_MASTER_TIMER)); // clear IRQ flag
	gpio_clear(GPIO_PORT(MICROWIRE_MASTER_SCK_PIN), GPIO_PIN(MICROWIRE_MASTER_SCK_PIN)); // ensure clock is idle low
	gpio_clear(GPIO_PORT(MICROWIRE_MASTER_SDO_PIN), GPIO_PIN(MICROWIRE_MASTER_SDO_PIN)); // ensure output is idle low
}


/** read bit from microwire communication
 *  @return bit value (true = '1', false = '0')
 */
static bool microwire_master_read_bit(void)
{
	microwire_master_wait_clock(); // wait for clock timing
	gpio_set(GPIO_PORT(MICROWIRE_MASTER_SCK_PIN), GPIO_PIN(MICROWIRE_MASTER_SCK_PIN)); // make rising edge for slave to output data
	microwire_master_wait_clock(); // wait for signal to be stable
	gpio_clear(GPIO_PORT(MICROWIRE_MASTER_SCK_PIN), GPIO_PIN(MICROWIRE_MASTER_SCK_PIN)); // set clock low again
	return 0 != gpio_get(GPIO_PORT(MICROWIRE_MASTER_SDI_PIN), GPIO_PIN(MICROWIRE_MASTER_SDI_PIN)); // read input signal
}

void microwire_master_read(uint32_t address, uint16_t* data, size_t length)
{
	// to sanity checks
	if (NULL == data || 0 == length || 0 == mirowire_master_address_size) { // can't save data
		return;
	}

	microwire_master_start(0x02, address); // send '10' READ instruction and memory address

	// there should already be a '0' dummy bit
	if (0!=gpio_get(GPIO_PORT(MICROWIRE_MASTER_SDI_PIN), GPIO_PIN(MICROWIRE_MASTER_SDI_PIN))) { // the dummy bit wasn't '0'
		goto clean;
	}

	// read data
	for (size_t i = 0; i < length; i++) {
		for (uint8_t b = (mirowire_master_organization_x16 ? 16 : 8); b > 0; b--) {
			if (microwire_master_read_bit()) { // read bit, MSb first
				data[i] |= (1 << (b - 1));	// set bit
			} else {
				data[i] &= ~(1 << (b - 1)); // clear bit
			}
		}
	}

clean:
	microwire_master_stop(); // stop communication and clean up
}

void microwire_master_write_enable(void)
{
	// to sanity checks
	if (mirowire_master_address_size < 2) { // can't send '11...' address
		return;
	}

	microwire_master_start(0x0, 0x3 << (mirowire_master_address_size - 2)); // send '00' WEN operation code and '11...' address
	microwire_master_stop(); // clean up
}

void microwire_master_write_disable(void)
{
	// to sanity checks
	if (mirowire_master_address_size < 2) { // can't send '00...' address
		return;
	}

	microwire_master_start(0x0, 0); // send '00' WDS operation code and '00...' address
	microwire_master_stop(); // clean up
}

void microwire_master_write(uint32_t address, uint16_t data)
{
	// to sanity checks
	if (0==mirowire_master_address_size) { // can't send address
		return;
	}

	microwire_master_start(0x01, address); // send '01' WRITE operation code and memory address

	// write data (MSb first)
	for (uint8_t b=(mirowire_master_organization_x16 ? 16 : 8); b>0; b--) {
		if (data&(1<<(b-1))) { // bit is set
			microwire_master_send_bit(true); // send '1' data bit
		} else {
			microwire_master_send_bit(false); // send '0' data bit
		}
	}

	microwire_master_stop(); // clean up
}

void microwire_master_wait_ready(void)
{

	// initial setup
	gpio_clear(GPIO_PORT(MICROWIRE_MASTER_SCK_PIN), GPIO_PIN(MICROWIRE_MASTER_SCK_PIN)); // ensure clock is low (to sample on rising edge)
	timer_set_counter(TIM(MICROWIRE_MASTER_TIMER), 0); // reset timer counter
	timer_clear_flag(TIM(MICROWIRE_MASTER_TIMER), TIM_SR_UIF); // clear timer flag
	nvic_clear_pending_irq(NVIC_TIM_IRQ(MICROWIRE_MASTER_TIMER)); // clear IRQ flag (else event doesn't wake up)
	timer_enable_counter(TIM(MICROWIRE_MASTER_TIMER)); // start timer to generate timing


	// SDI low on busy, high on ready, clock is ignored
	while (!microwire_master_read_bit()); // wait until slave is ready

	microwire_master_stop(); // clean up
}

void microwire_master_erase(uint32_t address)
{
	// sanity checks
	if (0==mirowire_master_address_size) { // can't send address
		return;
	}

	microwire_master_start(0x03, address); // send '11' ERASE operation code and memory address
	microwire_master_stop(); // clean up
}

void microwire_master_erase_all(void)
{
	// sanity checks
	if (mirowire_master_address_size < 2) { // can't send '11...' address
		return;
	}

	microwire_master_start(0x00, 0x2 << (mirowire_master_address_size - 2)); // send '00' ERAL operation code and '10...' address
	microwire_master_stop(); // clean up
}

void microwire_master_write_all(uint16_t data)
{
	// sanity checks
	if (0 == mirowire_master_address_size) { // can't send address
		return;
	}

	microwire_master_start(0x00, 0x1 << (mirowire_master_address_size - 2)); // send '00' WRAL operation code and '01...' address
	// write data (MSb first)
	for (uint8_t b = (mirowire_master_organization_x16 ? 16 : 8); b > 0; b--) {
		if (data&(1 << (b - 1))) { // bit is set
			microwire_master_send_bit(true); // send '1' data bit
		} else {
			microwire_master_send_bit(false); // send '0' data bit
		}
	}

	microwire_master_stop(); // clean up
}