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
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
- 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
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
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
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
- 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
- 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
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

Digital Input with Pull-up
Resistor
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
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
#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
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)
PWM is a technique to
use digital values and
delays to emulate
analog values

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

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

DC motor control with Arduino (3)
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)
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)
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)
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
// 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
If we need Audio processing, oscilloscope or EEG device
Arduino Zero or STM32 have built-in DMA controllers

Optimization with DMA
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
- 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)
Source: https://github.com/debsahu/ESP32_FFT_Audio_LEDs
Using an Arduino clone such as: ESP32 or Lolin D32

7 bin Equalizer (2)
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)
- Using hardware FFT IC MSGEQ7
- Predefined bins
- The Arduino microcontroller is relieved (FFT very CPU intensive)

Refernces
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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