How to use an Arduino

Contents INTRODUCTION TO ARDUINO 1. General information - Specification - Drivers and Shields - GPIO - Compilers and IDEs - Hardware protocols: I2C, SPI, UART 2. Examples - DC Motor control - Stepper motor control - Reading analog data ADC - What is DMA optimization? - Equalizer in software and hardware

In a nutshell INTRODUCTION TO ARDUINO Arduino is: • Board + Microcontroller unit (MCU) • A standard (Arduino comtible/clone) Arduino’s features: - 8 bit 32 registers RISC processor, AVR family - Produced by Atmel (acquired by Microchip Technology) - In-system programmer - Bootloader - Analog to Digital Converter (ADC) - 10-bit ADC with 1,024 (2^10) discrete analog levels - 14 input/output pins - Comes with IDE (Integrated Development Environment) - Many libraries, examples and documentation

Specification INTRODUCTION TO ARDUINO - 8 bit AVR CPU - Flash Memory is 32 KB - SRAM is 2 KB (RAM) - EEPROM is 1 KB - CLK Speed is 16-20 MHz - Some versions have DMA - 32bit ARM CPU - Flash Memory is 512 KB - SRAM is 96 KB - EEPROM is 1 KB - CLK Speed is 74-80 MHz - Has RTC - Has DMA Arduino Arduino clone STM32 Nucleo Many clones of Arduino exist often with better hardware parameters, Bluetooth and WIFI modules built-in Arduino also has several versions: UNO, Leonardo, Mega, Ethernet

Drivers and Shields INTRODUCTION TO ARDUINO Example: the L298N first as a driver and then a shield Difference: - A motor driver is a chip that drives motors. A motor shield is a circuit board with connections on it that contains a motor driver chip that drives motors. A shield is convenient since you can just plug it in to your Arduino and wire the motors direct to it, but it lacks the flexibility of a raw driver chip which you can wire up precisely as your project demands. Other popular shields for Arduino: ethernet, WIFI, RGB LCD

Arduino vs Raspberry Pi Short Comparison INTRODUCTION TO ARDUINO Pi is more powerful, like a normal computer Raspberry Pi is: - Multicore ARM 1.2Ghz,integrated GPU, RAM 1GB - Has GPIO 40 pins compared to Arduino’s 20 - 8 channel 17 bit ADC Usage: - For higher level tasks - Machine Learning (any ML library that compiles on Linux OpenCV included), Image Processing - Multimedia - Small factor computers - Surveillance systems - Draws more energy than Arduino - More expensive - Has no storage by default Arduino can be used as a slave for Raspberry Pi

Compilers INTRODUCTION TO ARDUINO Arduino program/sketch Small modifications to produce standard C code Every manufacturer has its own software development toolchain Avr-g++ compiler is part of Atmel AVR GNU Toolchain. It is based on GNU GCC and tools created by AVR Code for STM32 is pure C/C++ with libraries from ST. The compiler is part of the STM32Cube Ecosystem. The compiler is called GNU Tools for STM32 and it based on a patched version GNU Arm Embedded Toolchain avr-g++ compiler

CircuitPython INTRODUCTION TO ARDUINO - Fork of MicroPython - Targets: low memory and performance boards - 32 bit ARM (such as STM32 or ESP8266) - But not the original Arduino with 8 bit AVR CPU - Python 3 compiler and Virtual Machine are on the board - REPL on the USB through serial - Controller’s flash memory is exposed as USB thumb drive - .py files can be copied onto the board and executed - main.py or code.py are executed automatically on restart - Can restart automatically when .py file has changed - Result of “print” command is visible in the Serial Monitor - Can have only the VM and bytecode compiled program on the board

IDEs INTRODUCTION TO ARDUINO - Arduino IDE - Programs are called sketches - Easy program upload - Easy configuration - Serial Port - Arduino type or clone - Atom IDE + Platformio plugin - Visual Studio with Arduino add-on - Paid - Integrated debugging - Eclipse for Arduino - SMT32 System Workbench (only for STM32) - STM32CubeIDE (only for STM32)

Arduino GPIO INTRODUCTION TO ARDUINO General-Purpose Input Output (GPIO) 14 digital and 6 analog pins ca be used for both input and output pinMode (3, OUTPUT) //set as output digitalWrite (3, HIGH) //set 3,3V value digitalRead(pin) //read state digitalRead(pin) // ADC 5v -> [0..1023]

Arduino PINS INTRODUCTION TO ARDUINO

Digital Input with Pull-up Resistor INTRODUCTION TO ARDUINO Problem: Sometimes switching between one state to another or pins configured as input with nothing connected to them may arise situation of High-impedance state i.e. floating state. This state may report random changes in pin state Solution: Adding pull-up (to +5V) or pull-down (to Gnd) resistor which helps to set the input to a known state pinMode (3, INPUT_PULLUP) Pull Down resistor

SPI and I2C INTRODUCTION TO ARDUINO When we connect a microcontroller to a sensor, display, or other module these device needs to communicate Two popular hardware communication protocols: - SPI is used for SD cards, RFID card readers … - I2C is used for OLED displays, barometric pressure sensors, or gyroscope/accelerometer … - Both use clocks, are serial and async - 2 (I2C) or 4 (SPI) wires - One or multiple masters (I2C) - One or multiple slaves (both) - I2C uses messages with addresses to communicate with salves, SPI use selects to which slave to speak - Speed of transfer (SPI is faster) I2C message I2C: SDA (Serial Data) and SDL (Serial Clock)

I2C OLED example INTRODUCTION TO ARDUINO #include <Arduino.h> #include <U8g2lib.h> //library for control of the OLED screen #include <SPI.h> #include <Wire.h> U8G2_SSD1306_128X32_UNIVISION_F_HW_I2C u8g2(U8G2_R0); void setup(void) { u8g2.begin(); } void loop(void) { u8g2.clearBuffer(); //clear the internal memory u8g2.setFont(u8g2_font_logisoso28_tr); u8g2.drawStr(8,29,“GIPSALAB"); //write something to the internal memory u8g2.sendBuffer();//transfer internal memory to the display } On the Arduino: Pin 19 blue line is SCL Pin 18 purple is SCA

UART INTRODUCTION TO ARDUINO UART is used over a computer or peripheral device serial port (COM1,COM2…) through a UART chip Characteristics: - Well documented and widely used - Two wires - 9 bit packet (0 or 1 parity bits) - Serial - No clock - Has a parity bit to allow for error checking - No multiple slaves, only one on one

PWM (1) INTRODUCTION TO ARDUINO PWM is a technique to use digital values and delays to emulate analog values

DC motor control With Arduino (1) INTRODUCTION TO ARDUINO In red the L298N motor driver

DC motor control With Arduino (2) INTRODUCTION TO ARDUINO L298N H-bridge can used for two motors and to change in which direction the motor spins

DC motor control with Arduino (3) INTRODUCTION TO ARDUINO We use PWM in the range of [0 255]. So if want 3V out of 12V maximum then we need to send the value of 255/4 on the control pin 255 corresponds to 12 volts

DC motor control with Arduino (4) INTRODUCTION TO ARDUINO int rotDirection = 0; int pressed = false; #define button 4 void loop() { // Read potentiometer value int potValue = analogRead(A0); // Map the potentiometer value from 0 to 255 int pwmOutput = map(potValue, 0, 1023, 0 , 255); // Send PWM signal to L298N Enable pin analogWrite(enA, pwmOutput); // Read button if (digitalRead(button) == true) { pressed = !pressed; } //wait until button is released on a single push while (digitalRead(button) == true); delay(20); //If button is pressed - change rotation direction if (pressed == true & rotDirection == 0) { digitalWrite(in1, HIGH); digitalWrite(in2, LOW); rotDirection = 1; delay(20); } // If button is pressed - change rotation direction if (pressed == false & rotDirection == 1) { digitalWrite(in1, LOW); digitalWrite(in2, HIGH); rotDirection = 0; delay(20); } } //end of loop()

Stepper motor control with Arduino (1) INTRODUCTION TO ARDUINO Stepper motors can be: • unipolar -> U2004 Darlington Array • Bipolar -> SN754410ne H-Bridge Also the wiring is different for Darlington Array and the H-Bridge

Stepper motor control with Arduino (2) INTRODUCTION TO ARDUINO Code is the same for unipolar and bipolar motors. #include <Stepper.h> const int stepsPerRevolution = 200; // change this to fit the number of steps per revolution // for your motor // initialize the stepper library on pins 8 through 11: Stepper myStepper(stepsPerRevolution, 8, 9, 10, 11); int stepCount = 0; // number of steps the motor has taken void setup() { // nothing to do inside the setup} void loop() { // read the sensor value: int sensorReading = analogRead(A0); // map it to a range from 0 to 100: int motorSpeed = map(sensorReading, 0, 1023, 0, 100); // set the motor speed: if (motorSpeed > 0) { myStepper.setSpeed(motorSpeed); // how many RPMs per minute myStepper.step(stepsPerRevolution / 100); //2 steps } }

Reading analog data example INTRODUCTION TO ARDUINO // the setup routine runs once when you press reset: void setup() { // initialize serial communication at 9600 bits per second: Serial.begin(9600); } // the loop routine runs over and over again forever: void loop() { // read the input on analog pin 0: int sensorValue = analogRead(A0); // print out the value you read: Serial.println(sensorValue); //data is send over UART delay(1); // delay in between reads for stability } Reads an analog input on pin 0, prints the result to the Serial Monitor

DMA – Direct Memory Access INTRODUCTION TO ARDUINO If we need Audio processing, oscilloscope or EEG device Arduino Zero or STM32 have built-in DMA controllers

Optimization with DMA INTRODUCTION TO ARDUINO Processing (ADC + data forwarding to UART) takes 9.6 μs (microsecond) without DMA and 2 μs with DMA. That makes 4 times the difference.

Signal Processing on Arduino INTRODUCTION TO ARDUINO - Do we need to do it in real-time? - Are there space and energy constraints (flying air sensor)? - Is the ADC in Arduino good enough? - 10 bit ADC => 1,024 (2^10) discrete analog levels - ~1 KHz real world sampling / 9.6 KHz theoretical - RAM limit (2KB – 96 KB) - Is there enough libraries? - FIR: https://www.arduinolibraries.info/libraries/fir-filter - FFT: https://www.arduinolibraries.info/libraries/arduino-fft - Can we augment the Arduino to do better DSP?

7 bin Equalizer (1) INTRODUCTION TO ARDUINO Source: https://github.com/debsahu/ESP32_FFT_Audio_LEDs Using an Arduino clone such as: ESP32 or Lolin D32

7 bin Equalizer (2) INTRODUCTION TO ARDUINO Using software implemented FFT - We can choose each bin frequency - FFT https://github.com/kosme/arduinoFFT - Bins to LED conversion: https://github.com/G6EJD/ESP32-8266-Audio-Spectrum-Display

7 bin Equalizer (3) INTRODUCTION TO ARDUINO - Using hardware FFT IC MSGEQ7 - Predefined bins - The Arduino microcontroller is relieved (FFT very CPU intensive)

Refernces INTRODUCTION TO ARDUINO NUCLEO DMA: https://www.digikey.fr/en/maker/projects/getting-started-with-stm32- working-with-adc-and-dma/f5009db3a3ed4370acaf545a3370c30c https://www.youtube.com/watch?v=EsZLgqhqfO0 Arduino ZERO DMA: https://github.com/manitou48/ZERO DC motor control: https://howtomechatronics.com/tutorials/arduino/arduino-dc-motor- control-tutorial-l298n-pwm-h-bridge/ Stepper motor control: https://www.arduino.cc/en/tutorial/stepperSpeedControl Support for STM32 in Arduino: https://github.com/rogerclarkmelbourne/Arduino_STM32

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