//
// picostrip.cpp
//
#include "picostrip.h"
#include "ws2812.pio.h"
#include "pico/stdlib.h"
#include <stdlib.h>
#include <string.h>

// WS2812B bit cell is 1.25us; the PIO program spends 10 cycles per bit.
static const float WS2812_FREQ = 800000.0f;

// Datasheet reset is >50us of low. 300us is the commonly used safe value and
// costs nothing at this frame rate.
static const uint64_t WS2812_RESET_US = 300;

CPicoLEDStrip::CPicoLEDStrip (unsigned nLEDCount, unsigned nPin)
:	m_nLEDCount (nLEDCount),
	m_nPin (nPin),
	m_pBuffer (nullptr),
	m_PIO (nullptr),
	m_nSM (0),
	m_nOffset (0),
	m_bInitialized (false),
	m_nLastFrameUs (0)
{
}

CPicoLEDStrip::~CPicoLEDStrip (void)
{
	free (m_pBuffer);
	m_pBuffer = nullptr;
}

bool CPicoLEDStrip::Initialize (void)
{
	m_pBuffer = (uint32_t *) calloc (m_nLEDCount, sizeof (uint32_t));
	if (m_pBuffer == nullptr)
	{
		return false;
	}

	// Let the SDK place the program on whichever PIO block has room, so
	// this cannot collide with anything else added later.
	if (!pio_claim_free_sm_and_add_program_for_gpio_range (
			&ws2812_program, &m_PIO, &m_nSM, &m_nOffset, m_nPin, 1, true))
	{
		return false;
	}

	ws2812_program_init (m_PIO, m_nSM, m_nOffset, m_nPin, WS2812_FREQ);

	m_bInitialized = true;
	m_nLastFrameUs = time_us_64 ();

	return true;
}

void CPicoLEDStrip::SetLED (unsigned nIndex, uint8_t nRed, uint8_t nGreen, uint8_t nBlue)
{
	if (nIndex >= m_nLEDCount)
	{
		return;
	}

	// WS2812B wants GRB. The PIO shifts out MSB first with a 24-bit
	// threshold, so the triple is left-justified in the word.
	m_pBuffer[nIndex] =   ((uint32_t) nGreen << 24)
			    | ((uint32_t) nRed   << 16)
			    | ((uint32_t) nBlue  <<  8);
}

void CPicoLEDStrip::WaitForLatch (void)
{
	uint64_t nElapsed = time_us_64 () - m_nLastFrameUs;
	if (nElapsed < WS2812_RESET_US)
	{
		busy_wait_us (WS2812_RESET_US - nElapsed);
	}
}

bool CPicoLEDStrip::Update (void)
{
	if (!m_bInitialized)
	{
		return false;
	}

	WaitForLatch ();

	for (unsigned i = 0; i < m_nLEDCount; i++)
	{
		// Blocking push. The FIFO drains at 800kbit/s, so this paces the
		// loop naturally and needs no DMA at this strip length.
		pio_sm_put_blocking (m_PIO, m_nSM, m_pBuffer[i]);
	}

	m_nLastFrameUs = time_us_64 ();

	return true;
}

bool CPicoLEDStrip::Blackout (void)
{
	memset (m_pBuffer, 0, m_nLEDCount * sizeof (uint32_t));

	return Update ();
}