/************************************************************************

  M5StackFire simple oscilloscope example

  The oscilloscope has a auto trigger function to achive a stable
  visual impression when a repeating signal like a sine wave is applied.

  original version
  STM32F429 Discovery June 2018, ChrisMicro
  this version reworked for
  M5StackFire         September 2018, ChrisMicro

************************************************************************/
#include <M5Stack.h>

#define M5STACKFIRE_MICROPHONE_PIN 34
#define M5STACKFIRE_SPEAKER_PIN    25  // speaker DAC, only 8 Bit

#define HORIZONTAL_RESOLUTION 320
#define VERTICAL_RESOLUTION   240
#define POSITION_OFFSET_Y     20
#define SIGNAL_LENGTH         HORIZONTAL_RESOLUTION

uint16_t oldSignal[SIGNAL_LENGTH];
uint16_t adcBuffer[SIGNAL_LENGTH];

#define SAMPLING_TIME_US    25
#define ANALOG_SIGNAL_INPUT M5STACKFIRE_MICROPHONE_PIN

void setup() {
    dacWrite(M5STACKFIRE_SPEAKER_PIN,
             0);  // make sure that the speaker is quite
    M5.Lcd.begin();
    M5.Power.begin();
    M5.Lcd.fillScreen(BLACK);
    M5.Lcd.fillRect(10, 1, 150, 160, BLACK);
    M5.Lcd.setCursor(0, 0);
    M5.Lcd.setTextColor(GREEN);  // M5.Lcd.setTextSize(3);
    M5.Lcd.setTextSize(1);

    M5.Lcd.println("analog input MIC");
    M5.Lcd.print("sampling frequency: ");
    M5.Lcd.print(1000000 / SAMPLING_TIME_US);
    M5.Lcd.println(" Hz");
}

void waitForAutoTrigger() {
    uint32_t triggerLevel = 512;
    uint32_t hysteresis   = 10;
    uint32_t timeOut_ms   = 100;

    uint32_t timeOutLimit = millis() + timeOut_ms;
    uint32_t timeOutFlag  = false;

    uint32_t adcValue = 0;

    adcValue = analogRead(ANALOG_SIGNAL_INPUT);

    // wait for low level
    while ((adcValue > triggerLevel - hysteresis) && !timeOutFlag) {
        adcValue = analogRead(ANALOG_SIGNAL_INPUT);

        if (millis() > timeOutLimit) timeOutFlag = 1;
    }

    if (!timeOutFlag) {
        // wait for high level
        while ((adcValue < triggerLevel + hysteresis) &&
               (millis() < timeOutLimit)) {
            adcValue = analogRead(ANALOG_SIGNAL_INPUT);
        }
    }
}

void showSignal() {
    int n;

    int oldx;
    int oldy;
    int oldSig;
    int x, y;

    for (n = 0; n < SIGNAL_LENGTH; n++) {
        x = n;
        y = map(adcBuffer[n], 0, 4096, VERTICAL_RESOLUTION, POSITION_OFFSET_Y);

        if (n > 0) {
            // delete old line element
            M5.Lcd.drawLine(oldx, oldSig, x, oldSignal[n], BLACK);

            // draw new line element
            if (n < SIGNAL_LENGTH - 1)  // don't draw last element because it
                                        // would generate artifacts
            {
                M5.Lcd.drawLine(oldx, oldy, x, y, GREEN);
            }
        }
        oldx         = x;
        oldy         = y;
        oldSig       = oldSignal[n];
        oldSignal[n] = y;
    }
}

void loop(void) {
    int n;
    uint32_t nextTime = 0;

    waitForAutoTrigger();

    // record signal
    for (n = 0; n < SIGNAL_LENGTH; n++) {
        adcBuffer[n] = analogRead(ANALOG_SIGNAL_INPUT);

        // wait for next sample
        while (micros() < nextTime)
            ;
        nextTime = micros() + SAMPLING_TIME_US;
    }

    showSignal();
}