Intro to Arduino

Fig.: Arduino UNO Rev 3. CPU: Microchip (Atmel) ATmega328p, 8-bit AVR Core. https://store.arduino.cc/arduino-uno-rev3

Technical data (Arduino UNO processor)

• Microcontroller ATmega328P
• Operating Voltage 5V
• Input Voltage (recommended) 7-12V
• Input Voltage (limit) 6-20V
• Digital I/O Pins 14 (of which 6 provide PWM output)
• PWM Digital I/O Pins 6
• Analog Input Pins 6
• DC Current per I/O Pin 20 mA
• DC Current for 3.3V Pin 50 mA
• Flash Memory 32 KB (ATmega328P) of which 0.5 KB used by bootloader
• SRAM 2 KB (ATmega328P)
• EEPROM 1 KB (ATmega328P)
• Clock Speed 16 MHz
• https://store.arduino.cc/arduino-uno-rev3

• Lecture 6 – Introduction to the ATmega328 and Arduino
• Lecture 7 – ATmega328 Timers and Interrupts

The CPU used is ATmega328p having been designed by the former company Atmel which has been taken over by Microchip.

Please follow the instructions on Getting started with the Arduino and Genuino UNO.

We have to learn the following commands:

pinMode(pin, mode) 
myval = digitalRead(pin)
digitalWrite(pin, value)
myval = analogRead(pin)
analogWrite(pin, value)
delay(ms)
Serial.begin(baudrate)
Serial.println(data)
map(value, fromLow, fromHigh, toLow, toHigh)

Keywords: Arduino IDE, directories, libraries, code files, compile, upload, terminal (monitor)

<note> For the following exercises use the
Arduino Online Language Reference and the
Programmers Notebook (pdf) by Brian Evans. </note>

Write a program which lets and LED blink “SOS” in Morse code:

. . .   - - -  . . . 

(three short, three long, three short blinks). The LED is connected to pin 13. By default all pins are input so you have to define the pin direction to be an output explicitly. Use digitalWrite(pin,HIGH) and digitalWrite(pin,LOW).

Write two functions void morse_S() and void morse_O() and use for next loops for the loops within the functions.

Write two functions void blink_short() and void blink_long() including the pauses (LED off).

<note important> ATTENTION: 3.3V or 5V?
Some Arduino platforms use 3.3V as supply voltage or VCC (not 5V). In this case you might damage the microcontroller if you connect 5V to its pins! The input voltage would exceed the supply voltage (overvoltage). Avoid this! Some microcontrollers with 3.3V VCC have 5V tolerant inputs but this is not generally the case! Read the MC datasheets. </note>

• How to connect switches to digital inputs: Why do we have to use pull-up or pull-down resistors?
• How to use and activate internal pull-up resistors of ATmega328 GPIO pins
• If buttonPressed() then … else … endif
• Switches are prone to bouncing. How can we demonstrate bouncing? Oscilloscope …
• How to debounce?

• Resolution of ADC? How many bits? How many different amplitude values?
• Connect a potentiometer to an analog input of Arduino:
  The outer pins are connected to GND and VCC, respectively.
  The middle terminal is connected to the ADC.

• Read the values from the ADC and write them to the serial port.
• What are min and max values?
• How many bits resolution does the ADC have?
• Use the function map() to transform the ADC values to an interval of 0 to 100.

The “old” AVR microcontrollers such as ATmege328, the core of Arduino UNO, do not have a real analog output. To work around this limitation a method called Pulse Width Modulation (PWM) is used. A square wave signal of fixed frequency is generated and provided at a port pin (digital output). The pulse width of the square wave (the time for the signal being logic high) can be changed whereas the total signal period T is kept constant (as a result of constant frequency).

The ratio $r = \mathrm{\frac{pulse\;width}{period}}$ is called duty cycle.

The average voltage of the signal is then a linear function of $r$:

$V_\mathrm{avg} = r\cdot V_\mathrm{cc} + (1-r)\cdot 0V = r\cdot V_\mathrm{cc}$

• Use the function “analog_out()”. Observe the output signal with the oscilloscope.
• Resolution of PWM? How many bits? How many different amplitude values?
• Read values from a potentiometer (10 bit), map the values to an 8 bit range
  and use the scaled value for a PWM output. Dim a LED.

• SPI
• TWI (two wire interface), I2C
• 1-Wire