Fig. 1
From: Design and implementation of a simple and inexpensive respiratory synchronization control platform
The Arduino UNO is a popular and inexpensive open-source microcontroller board based on the ATmega328P microcontroller. The board features 14 digital pins and 6 analog input pins (featuring 10-bit ADC resolution). Also, 6 of the 14 digital pins can be configured as pseudo-analog output pins, with the analog outputs being simulated using PWM (pulse width modulation). The Arduino UNO can be powered using a USB cable or externally via a 7–20-V source, such as an ordinary 9-V battery. It also features a clock speed of 16 MHz, support for external interrupts, and a built-in LED driven by digital pin 13. Programming the Arduino UNO (and other family members) is usually done via the Arduino integrated development environment (IDE), available as a free download for the Windows, macOS, and Linux operating systems. Image credit: https://commons.wikimedia.org/wiki/File:Arduino_Uno_-_R3.jpg. Image used under the Creative Commons Attribution 2.0 Generic license
