Blink Example for LGT8F328P

#include <Arduino.h>

/*
 * LGT8F328P GPIO Output Test
 * ---------------------------------------------------------------------------
 *
 * Four GPIOs toggle synchronously between two states:
 *
 *   PIN_ACTIVE_HIGH (D5, HDR on)
 *     Phase 1: HIGH
 *     Phase 2: LOW
 *     Push-pull output in both states.
 *
 *   PIN_ACTIVE_LOW (D6, HDR on)
 *     Phase 1: LOW
 *     Phase 2: HIGH
 *     Push-pull output in both states.
 *
 *   PIN_LOW_HIZ (D4, HDR off)
 *     Phase 1: LOW
 *     Phase 2: High impedance (input)
 *     The GPIO actively pulls LOW but never drives HIGH.
 *     Intended for signals such as the SY8750 PWM input:
 *       LOW  = SY8750 disabled / LED OFF
 *       Hi-Z = SY8750 internal pull-up / LED ON
 *
 *   PIN_HIGH_HIZ (D3, HDR off)
 *     Phase 1: HIGH
 *     Phase 2: High impedance (input)
 *     The GPIO actively drives HIGH but never drives LOW.
 *
 * D5 and D6 are configured for LGT8F328P High Drive (HDR):
 *   HDR0 = D5 / PD5
 *   HDR1 = D6 / PD6
 *
 * D3 and D4 use their normal GPIO drive capability.
 *
 * Blink timing is controlled by ON_TIME_MS and OFF_TIME_MS.
 */

// -----------------------------------------------------------------------------
// Configuration
// -----------------------------------------------------------------------------

constexpr uint32_t ON_TIME_MS  = 400;
constexpr uint32_t OFF_TIME_MS = 400;

constexpr uint8_t PIN_ACTIVE_HIGH = 5;  // D5, HDR0
constexpr uint8_t PIN_ACTIVE_LOW  = 6;  // D6, HDR1
constexpr uint8_t PIN_LOW_HIZ     = 4;  // D4, LOW / Hi-Z
constexpr uint8_t PIN_HIGH_HIZ    = 3;  // D3, HIGH / Hi-Z

// -----------------------------------------------------------------------------
// Setup
// -----------------------------------------------------------------------------

void setup()
{
    pinMode(LED_BUILTIN, OUTPUT);

    // Enable LGT8F328P High Drive for D5 (HDR0) and D6 (HDR1).
    HDR |= (1 << HDR0) | (1 << HDR1);

    // D5 and D6 remain push-pull outputs.
    pinMode(PIN_ACTIVE_HIGH, OUTPUT);
    pinMode(PIN_ACTIVE_LOW, OUTPUT);

    // D4 and D3 start electrically disconnected (high impedance).
    pinMode(PIN_LOW_HIZ, INPUT);
    pinMode(PIN_HIGH_HIZ, INPUT);
}

// -----------------------------------------------------------------------------
// Main loop
// -----------------------------------------------------------------------------

void loop()
{
    // -------------------------------------------------------------------------
    // Phase 1
    //
    // D5 / ACTIVE_HIGH : HIGH
    // D6 / ACTIVE_LOW  : LOW
    // D4 / LOW_HIZ     : LOW
    // D3 / HIGH_HIZ    : HIGH
    // -------------------------------------------------------------------------

    digitalWrite(LED_BUILTIN, HIGH);

    digitalWrite(PIN_ACTIVE_HIGH, HIGH);
    digitalWrite(PIN_ACTIVE_LOW, LOW);

    // D4: actively pull LOW.
    // Set the output latch first to prevent a momentary HIGH pulse when the
    // output driver is enabled.
    digitalWrite(PIN_LOW_HIZ, LOW);
    pinMode(PIN_LOW_HIZ, OUTPUT);

    // D3: actively drive HIGH.
    // Set the output latch first before enabling the output driver.
    digitalWrite(PIN_HIGH_HIZ, HIGH);
    pinMode(PIN_HIGH_HIZ, OUTPUT);

    delay(ON_TIME_MS);

    // -------------------------------------------------------------------------
    // Phase 2
    //
    // D5 / ACTIVE_HIGH : LOW
    // D6 / ACTIVE_LOW  : HIGH
    // D4 / LOW_HIZ     : Hi-Z
    // D3 / HIGH_HIZ    : Hi-Z
    // -------------------------------------------------------------------------

    digitalWrite(LED_BUILTIN, LOW);

    digitalWrite(PIN_ACTIVE_HIGH, LOW);
    digitalWrite(PIN_ACTIVE_LOW, HIGH);

    // INPUT without INPUT_PULLUP disables the output drivers, leaving D4 and
    // D3 electrically high-impedance.
    pinMode(PIN_LOW_HIZ, INPUT);
    pinMode(PIN_HIGH_HIZ, INPUT);

    delay(OFF_TIME_MS);
}