Output Devices

Learning Objectives

Assignments

Learning Section

Individual Assignments

Designing the Microcontroller Board

I decided to try something which involved buttons, sliders and enncoders for my final project - Symphoni The Record Player. But after seeing the class, I was amused by the capacitive touch and its capabilities. Therefore I decided my sensors for the week - Capacitive Touch Slider and Rotary Encoder. So I developed this board last week and tried to program the WS2812B LED Array

I refered to some previous works of students who used capacitive touch and SAMD21

WS812B Individually Addressable LEDs

The WS2812B uses 5V but my MCU uses 3.3 V logic level, therefore I needed the 5V output. So I had to make a logic level shifter. So I learned more about Logic Level Shifter.

I refered to this documentation Logic Level Shifters

Parameters

Adafruit_NeoPixel pixels(NUMPIXELS, PIN, NEO_GRB + NEO_KHZ800)

	#include 
	
	
	// Pin number of WS2812B
	#define PIN        11 // 
	
	// Number of WS2812B LEDs
	#define NUMPIXELS 5 
	
	// When setting up the NeoPixel library, we tell it how many pixels,
	// and which pin to use to send signals.
	Adafruit_NeoPixel pixels(NUMPIXELS, PIN, NEO_GRB + NEO_KHZ800);
	
	#define DELAYVAL 500 // Time (in milliseconds) to pause between pixels
	
	void setup() {
	
	
	  pixels.begin(); // INITIALIZE NeoPixel strip object (REQUIRED)
	}
	
	void loop() {
	  pixels.clear(); // Set all pixel colors to 'off'
	
	  // The first NeoPixel in a strand is #0, second is 1, all the way up
	  // to the count of pixels minus one.
	  for(int i=0; i < NUMPIXELS; i++) { 
		pixels.setPixelColor(i, pixels.Color(0, 150, 0));
	
		pixels.show();  
		delay(DELAYVAL); 
	  }
	}

	

Spotify Player

I used the last week's board and used the HID Library to control the functions.

#include 
#include 

#include "Adafruit_FreeTouch.h"
#include "Adafruit_NeoPixel.h"

Adafruit_FreeTouch t0 = Adafruit_FreeTouch(2, OVERSAMPLE_64, RESISTOR_0, FREQ_MODE_NONE);
Adafruit_FreeTouch t1 = Adafruit_FreeTouch(3, OVERSAMPLE_64, RESISTOR_0, FREQ_MODE_NONE);
Adafruit_FreeTouch t2 = Adafruit_FreeTouch(4, OVERSAMPLE_64, RESISTOR_0, FREQ_MODE_NONE);
Adafruit_FreeTouch t3 = Adafruit_FreeTouch(5, OVERSAMPLE_64, RESISTOR_0, FREQ_MODE_NONE);
Adafruit_FreeTouch t4 = Adafruit_FreeTouch(6, OVERSAMPLE_64, RESISTOR_0, FREQ_MODE_NONE);

// Rotary Encoder Inputs
#define CLK 9
#define DT 8
#define SW 10
#define PIN 11 

#define NUMPIXELS 5 
#define IDLE_TIME 3000  // Time in milliseconds to wait before idle effect


int lastDirection = 0;  // 1 = Right, -1 = Left
int isPlaying = 1;

int counter = 0;
int currentStateCLK;
int lastStateCLK;
unsigned long lastButtonPress = 0;

int baseline[5] = {1e6, 1e6, 1e6, 1e6, 1e6};

Adafruit_NeoPixel pixels(NUMPIXELS, PIN, NEO_GRB + NEO_KHZ800);

unsigned long lastActivityTime = 0;
bool isIdle = true;

void setup() {
	pinMode(CLK, INPUT);
	pinMode(DT, INPUT);
	pinMode(SW, INPUT_PULLUP);

	Consumer.begin();
	Keyboard.begin();
	Consumer.write(MEDIA_STOP);
	SerialUSB.begin(9600);

	pixels.begin();

	// Initialize FreeTouch sensors
	t0.begin(); t1.begin(); t2.begin(); t3.begin(); t4.begin();

	// Calibrate baseline
	for (int i = 0; i < 100; i++) {
		baseline[0] = min(baseline[0], t0.measure());
		baseline[1] = min(baseline[1], t1.measure());
		baseline[2] = min(baseline[2], t2.measure());
		baseline[3] = min(baseline[3], t3.measure());
		baseline[4] = min(baseline[4], t4.measure());
		delay(10);
	}

	lastStateCLK = digitalRead(CLK);
}

void showFlow(int direction) {
	isIdle = false;
	lastActivityTime = millis();

	for (int i = 0; i < NUMPIXELS; i++) {
		pixels.clear();

		for (int j = 0; j <= i; j++) {
			int index = (direction == 1) ? j : (NUMPIXELS - 1 - j);

			if (direction == 1) {  
				pixels.setPixelColor(index, pixels.Color(0, 255 - (j * 50), 0));  // Green Flow (Right)
			} else {  
				pixels.setPixelColor(index, pixels.Color(255 - (j * 50), 0, 0));  // Red Flow (Left)
			}
		}
		
		pixels.show();
		delay(50);
	}
}

void openSpotify() {
	Keyboard.press(KEY_LEFT_GUI); // Press Windows key (for Windows) or Command key (for Mac)
	Keyboard.press('r');  // Press 'R' to open Run dialog (Windows only)
	delay(200);
	Keyboard.releaseAll();

	delay(200);
	Keyboard.print("spotify");  // Type "spotify"
	delay(200);
	Keyboard.press(KEY_RETURN);  // Press Enter
	Keyboard.releaseAll();

	
	
}

void showIdleEffect() {
	static int brightness = 0;
	static int fadeDirection = 1;

	brightness += fadeDirection * 5;
	if (brightness >= 150 || brightness <= 0) {
		fadeDirection *= -1;
	}

	for (int i = 0; i < NUMPIXELS; i++) {
		if (isPlaying) {
			pixels.setPixelColor(i, pixels.Color(0, brightness, 0));  // Green when playing
		} else {
			pixels.setPixelColor(i, pixels.Color(300, 0, 0));  // Purple when paused
		}
	}

	pixels.show();
	delay(50);
}

void loop() {
	pixels.clear();

	currentStateCLK = digitalRead(CLK);

	if (currentStateCLK != lastStateCLK && currentStateCLK == 1) {
		if (digitalRead(DT) != currentStateCLK) {
			counter++;
			Consumer.write(MEDIA_VOLUME_UP);
			SerialUSB.println("Volume UP");
			lastDirection = 1;
			showFlow(lastDirection);
		} else {
			counter--;
			Consumer.write(MEDIA_VOLUME_DOWN);
			SerialUSB.println("Volume DOWN");
			lastDirection = -1;
			showFlow(lastDirection);
		}
	}

	lastStateCLK = currentStateCLK;

	int btnState = digitalRead(SW);

	if (btnState == LOW) {
		if (millis() - lastButtonPress > 200) {
			SerialUSB.println("Play/Pause");
			Consumer.write(MEDIA_PLAY_PAUSE);
		}
		lastButtonPress = millis();
	}

	int touchValues[5] = {
		t0.measure() - baseline[0],
		t1.measure() - baseline[1],
		t2.measure() - baseline[2],
		t3.measure() - baseline[3],
		t4.measure() - baseline[4]
	};

	if (touchValues[0] > 9) {
		Consumer.write(MEDIA_REWIND);
		SerialUSB.println("Rewind");
		delay(1000);
	}

	if (touchValues[1] > 9) {
		Consumer.write(MEDIA_PREVIOUS);
		SerialUSB.println("Previous");
		delay(1000);
	}

static unsigned long touchStartTime = 0;
static bool touchHeld = false;
static bool isSpotifyOpen = false;  // Track Spotify state

if (touchValues[2] > 9) {
	if (!touchHeld) {
		touchStartTime = millis();  // Start timer
		touchHeld = true;
	}

	if (millis() - touchStartTime > 2000) {  // If held for more than 2 seconds
		if (isSpotifyOpen) {
			Keyboard.press(KEY_LEFT_GUI);
		Keyboard.press('r');  // Open Run
		delay(200);
		Keyboard.releaseAll();

		delay(200);
		Keyboard.print("taskkill /IM spotify.exe /F");
		delay(200);
		Keyboard.press(KEY_RETURN);
		Keyboard.releaseAll();
		} else {
			SerialUSB.println("Opening Spotify");
			openSpotify();
		}
		
		isSpotifyOpen = !isSpotifyOpen;  // Toggle state
		touchHeld = false;  // Reset flag to prevent repeated triggers
	}
} else if (touchHeld) {
	// If released before 2 seconds, Play/Pause
	if (millis() - touchStartTime <= 2000) {
		isPlaying = !isPlaying;
		Consumer.write(MEDIA_PLAY_PAUSE);
		SerialUSB.println("Play/Pause");
	}
	touchHeld = false;  // Reset flag
}

	if (touchValues[3] > 9) {
		Consumer.write(MEDIA_NEXT);
		SerialUSB.println("Next");
		delay(1000);
	}

	if (touchValues[4] > 9) {
		Consumer.write(MEDIA_FAST_FORWARD);
		SerialUSB.println("Fast Forward");
		delay(500);
		if (touchValues[4] > 9) {
			Consumer.write(MEDIA_FAST_FORWARD);
		}
	}

	delay(5);

	if (millis() - lastActivityTime > IDLE_TIME) {
		isIdle = true;
		lastDirection = 0;  // **Fix: Reset direction when going idle**
	}

	if (isIdle) {
		showIdleEffect();
	}
}

Audio Amplifier Circuit

XIAO ESP32S3

I2S -

PT8211 I2S DAC

PT8211 is a dual channel, 16 bit Digital-to-Analog Converter IC utilizing CMOS technology specially designed for the digital audio applications. The internal conversion architecture is based on a R-2R resister ladder network, internal circuit is well matched and a 16 bit dynamic range is achieved even in whole supply voltage range. PT8211 also enhanced the performance of timing responsibility in digital serial bus, in a company with the fast switching R-2R network that make 8X oversampling audio signal is also supported. PT8211 can be supported wide range of sample frequency; it is compatible with TDA1311 by functionally. Its digital input timing format is Least Significant Bit Justified (LSBJ), or so called Japanese input format. Digital code format is two's complement and MSB first. PT8211 is available in 8-pin SOP or DIP.

The serial bus input data format of PT8211 is Japanese or called LSBJ (Least Significant Bit Justified) format. Each valid DIN data will be shifted to the input register in the rising edge of the BCK, only the first 16bit data ( from MSB) is valid if the input data length is more than 16bits, other data bit will be truncated. The clock frequency of the BCK could run up to 20MHz and supported to 8x over-sampling in 48KHz WS clock rate. Both left and right data words are time multiplexed.

LM4861 Amplifier

The LM4861 is a bridge-connected audio power 2• No output coupling capacitors, bootstrap amplifier capable of delivering 1.1W of continuous capacitors, or snubber circuits are necessary average power to an 8Ω load with 1% THD+N using

The output from XIAO ESP32S3 is digital I2S Signals through the pins WS(Word Select), BCLK(Bit Clock) and DIN(Data Pin). The

PCB Milling and Assembly

Testing the current and Power of my Board

I had to cut down the shorted traces because I had already soldered all the components and there was no time to mill a new board. That's why I had perform a major surgery on my board by using insulated wires and soldering it to connect it

Internet Radio using ESP32

1 KHz Test Wav from SD Card

10KHz Test Wav from SD Card

Power Delivery (PD)

USB Power Delivery is a common fast-charging standard that can be implemented in all USB-powered gadgets.

USB Power Delivery is much more powerful, supporting up to 240W of power to charge up even the most demanding gadgets such as laptops. It's also safer, as gadgets and chargers communicate with each other over the USB cable to confirm the optimal charging power level. This handshaking approach supports voltage steps at 5V, 9V, 15V, 20V, and beyond for power outputs ranging from 0.5W to 240W.

I needed 12V Output for my WS2811 Addressable LED Strip. That's why I used a Power Delivery module to power my 12V LED Strip

WS2811 LED Strip with Board

I used the example from Adafruit 'strandtest.ino'. I tested the 12V Addressable LEDs using the test code

I attached the LED Strip to the Media Cabinet that I made during the Computer Controlled Machining . This is where Symphoni - The Turntable will be placed. I wanted to use the board I designed last week and communicate with this week's board - Speaker

Hero Shots

Spotify Control

Learning Section

Logic Level Shifter in Falstad

Design Files

You can download my design files from below

• TouchNav SAMD21 Board

  Traces PNG Outline PNG Outline PNG
• KiCad Files Download ZIP

• AudioAmp Circuit XIAO ESP32s3

  Traces PNG Outline PNG Outline PNG
• KiCad Files Download ZIP