1 ‒ Core Idea

Arduino pairs open-source hardware (AVR/ARM micro-controllers) with a beginner-friendly IDE, libraries, and an active community—lowering the barrier for physical-computing projects.

2 ‒ Key Components

1. Boards: Uno, Nano, Mega 2560, Due, etc.
2. IDE/CLI: Sketch-oriented C/C++ with board manager & library manager.
3. Libraries: Thousands of install-on-click code packs.
4. Shields & Modules: Plug-and-play add-ons (Wi-Fi, SD, Motor, Audio, Bio-sensors).

3 ‒ Typical Workflow

1. Write .ino sketch in IDE.
2. Click Upload (compiles with avr-gcc, flashes over bootloader).
3. Observe Serial Monitor or connected peripherals.

1 ‒ Specs at a Glance

2 ‒ Why Mega for Signal Work?

• Plentiful ADC channels simplify multi-lead ECG, EMG, or microphone arrays.
• Multiple UARTs let you stream data to PC while talking to Bluetooth / Wi-Fi modules.
• 16-bit timers enable precise sample clocks up to ~44 kHz (with prescalers).
• Extra SRAM eases ring-buffers and real-time digital-filter kernels.

1 ‒ IDE (Windows / macOS / Linux)

1. Download from arduino.cc → install CH340/FTDI driver if clone board.
2. Select Tools → Board → Arduino Mega 2560 and serial port.
3. Add libraries via Sketch → Include Library → Manage Libraries…

2 ‒ arduino-cli & VS Code

$ brew install arduino-cli
$ arduino-cli core install arduino:avr
$ arduino-cli upload -b arduino:avr:mega -p /dev/ttyUSB0

3 ‒ Debugging Tips

• Use Serial.print() sparingly—excess I/O ruins timing.
• Set #define DEBUG_LEVEL 2 & wrap prints in if(DEBUG_LEVEL).
• For cycle-accurate tracing, add a $20 JTAG-ICE (Atmel-ICE clone) + avr-gdb.

1 ‒ Digital I/O

// LED Blink (pin 13)
void setup() {
  pinMode(13, OUTPUT);
}
void loop() {
  digitalWrite(13, HIGH);  delay(500);
  digitalWrite(13, LOW);   delay(500);
}

2 ‒ Analog Read (10-bit ADC)

const uint8_t ECG_IN = A0;
void setup() { Serial.begin(115200); }
void loop() {
  int sample = analogRead(ECG_IN);          // 0‒1023 → 0‒5 V
  Serial.println(sample);
}

3 ‒ Analog Output Options

• No true DAC on Mega; emulate audio via PWM + RC filter, or add MCP4921 SPI DAC.
• Timer-controlled PWM (31.25 kHz) reduces audible whine in audio DAC setups.

1 ‒ 1 kHz ADC Sampler (Timer5)

volatile uint16_t sample;
ISR(TIMER5_COMPA_vect){          // fires every 1 ms
  sample = analogRead(A0);
}
void setup() {
  noInterrupts();
  TCCR5A = 0;                   // CTC mode
  TCCR5B = (1<loop() {
  uint16_t s = sample;
  Serial.println(s);
}

2 ‒ Why Interrupts Matter

Busy-loop delays (delay()) jitter sampling; ISR-driven acquisition keeps timing deterministic for DSP & biomedical analysis.

1 ‒ Multiple UARTs

1. Serial USB CDC → PC logging
2. Serial1 → HC-05 Bluetooth
3. Serial2 → ESP-01 Wi-Fi (AT commands)
4. Serial3 → GPS, GSM, etc.

2 ‒ High-Speed SPI DAC

#include <SPI.h>
#define CS 10
void setup() {
  SPI.begin(); pinMode(CS, OUTPUT);
}
void writeDAC(uint16_t v){
  digitalWrite(CS, LOW);
  SPI.transfer(0x30 | (v>>8));  // MCP4921
  SPI.transfer(v & 0xFF);
  digitalWrite(CS, HIGH);
}

3 ‒ I²C Bio-Sensors

• MAX30102 SpO₂ & PPG
• ADS1115 16-bit ADC (±256 mV range) for EEG/EMG front-ends
• BME680 environmental compensation.

1 ‒ Sampling Considerations

• Nyquist: choose Fs ≥ 2 × f_max; for voice (4 kHz) use ≥ 8 kHz.
• ADC 10-bit → 60 dB SNR; external 12/16-bit improves fidelity.

2 ‒ FIR Low-Pass Example

const int16_t fir[5] = {2, 8, 12, 8, 2}; // simple 31 Hz LP @1 kHz
volatile uint16_t buf[5];
ISR(TIMER5_COMPA_vect){
  memmove(buf+1, buf, 4*sizeof(uint16_t));
  buf[0] = analogRead(A0);
  uint32_t acc=0;
  for(uint8_t i=0;i<5;i++) acc += buf[i]*fir[i];
  uint16_t y = acc>>8;              // scaled result
  Serial.write(highByte(y));
  Serial.write(lowByte(y));
}

3 ‒ Output Paths

1. PWM → RC filter → headphone amp
2. SPI-DAC → op-amp buffer
3. I²S codec (e.g., VS1053) via SPI for MP3 decoding

1 ‒ Analog Front-End (AFE)

• Instrumentation Amp (AD620/INA128) for μV-level biopotentials.
• Two-pole RC or Sallen-Key 40–250 Hz band-pass for ECG.
• Right-Leg-Drive bias reduces common-mode noise.

2 ‒ Isolation & Safety

Always power the patient side from battery only. Use optocouplers or ADuM digital isolators before USB connection.

3 ‒ Example ECG Sketch

#include <TimerOne.h>
void sendSample(){ Serial.println(analogRead(A0)); }
void setup() {
  Serial.begin(115200);
  Timer1.initialize(1000);     // 1 kHz
  Timer1.attachInterrupt(sendSample);
}
void loop(){}              // empty loop

4 ‒ Real-Time Analysis Ideas

1. Implement Pan-Tompkins algorithm for QRS detection.
2. Compute FFT bins for EMG median frequency fatigue study.
3. Smooth eye-blink artifacts in EEG via movingAverage().

1 ‒ Grounding & Layout

• Separate analog ground from digital ground; meet at star-point.
• Short (< 2 cm) traces between AFE and ADC pin.

2 ‒ Clock Noise Mitigation

1. Shield cables, twist differential leads.
2. Add 10 nF cap at AREF to reduce ripple.
3. Sample in ISR → buffer → process in loop().

3 ‒ Memory Management

Use static ring-buffers to avoid fragmentation; keep heap usage < 1 KB.

1 ‒ Reading

• Making Things Talk by Tom Igoe
• Practical Electronics for Inventors by Scherz & Monk
• NI PhysioBench signal databases for test data

2 ‒ Online Communities

1. Arduino Forum → Product Design > Audio
2. StackExchange / Electronics & Bioacoustics
3. GitHub → “arduino-ecg” & “arduino-dsp-libraries”

3 ‒ Upgrade Paths

• Teensy 4.x (600 MHz Cortex-M7, 2× I²S) for high-fidelity audio.
• STM32 Blue Pill with 12-bit ADC if you outgrow the Mega.
• Raspberry Pi + Mega → coarse real-time + heavy ML post-processing.