Introductory Medical Device Prototyping
Arduino Part 1 Prof. Steven S. Saliterman, http://saliterman.umn.edu/ Department of Biomedical Engineering, University of Minnesota
Prof. Steven S. Saliterman
Arduino Uno
Prof. Steven S. Saliterman
Power & Interface…
USB Interface
Digital I/O Pins Reset Button
ATMega Microcontroller
ICSP Connector
Power & Auxiliary Pins Analog –to - Digital Converter Pins
Debug LED
7 to 12 VDC Input
Prof. Steven S. Saliterman
USB Connection to Computer…
Prof. Steven S. Saliterman
Example Modules – Sensors…
Ultrasonic Sensor - HC-SR04 IR Sensor 2Y0A21 Sharp Digital Distance Sensor
MAX6675 Module + K Type Thermocouple Temperature Sensor
Diymall Bme280 Pressure Temperature Sensor Module with IIC I2c
SunFounder Accelerometer ADXL335
Prof. Steven S. Saliterman
9-Axis Absolute Orientation Sensor…
Absolute Orientation (Euler Vector, 100Hz) Three axis orientation data based on a 360° sphere.
Absolute Orientation (Quaterion, 100Hz) Four point quaternion output for more accurate data manipulation.
Angular Velocity Vector (100Hz) Three axis of 'rotation speed' in rad/s.
Acceleration Vector (100Hz) Three axis of acceleration (gravity + linear motion) in m/s^2.
Magnetic Field Strength Vector (20Hz) Three axis of magnetic field sensing in micro Tesla (uT).
Linear Acceleration Vector (100Hz) Three axis of linear acceleration data (acceleration minus gravity) in m/s^2.
Gravity Vector (100Hz) Three axis of gravitational acceleration (minus any movement) in m/s^2.
Temperature (1Hz) Ambient temperature in degrees celsius.
Courtesy of Adafruit
Sensor “fusion” combines the following measurements…
Prof. Steven S. Saliterman
Actuators…
2-Channel 5 V Solid State Relay Module
Standard Size - High Torque - Metal Gear Servo Stepper Motor
DC Motor with Gear
Prof. Steven S. Saliterman
User Interface…
Adafruit 1.8” Color TFT LCD Display with MicroSD Card Breakout – ST77 35R1.8" Color TFT LCD display with MicroSD Card Breakout - ST7735R
7-Segment Serial Display - Red
Diymall 0.96" Inch I2c IIC Serial 128x64 Oled LCD LED White Display Module
Mini ISD2548 Digital Voice Recorder
Prof. Steven S. Saliterman
Consider this Device Concept Task: Make a digital thermometer consisting of an enclosure, microcontroller board, thermocouple sensor, digital display, sound alert, slide switch, pushbutton and battery….
http://store-usa.arduino http://www.globalsources.com http://www.thermometricscorp.com
Prof. Steven S. Saliterman
Formulate an Algorithm…
1. When the pushbutton is pressed… Measure the temperature, Beep when the reading is good, Display the value for ten seconds, and finally Save the value to memory.
2. Start all over again. 3. Now flowchart this…
Prof. Steven S. Saliterman
Flowchart the Algorithm…
Display Temperature
& Beep
Start
Delay 10 Sec.
Monitor for Button Press
Button Pressed
?
Read Temperature
Valid Reading
?
Clear Display
Store Value
Stop
No
Yes
Yes
No
Prof. Steven S. Saliterman
Software & Programming
1. Software is the smart in your “smart device.” 2. An algorithm displayed as a flowchart, transforms your problem
into various input, processing, decision and output steps 3. Lines of code are written to implement your algorithm. 4. Code may be written in assembly language and/or higher level
languages such as C, C++, and C#. 5. A compiler converts your code into machine language that the
microcontroller understands. 6. The compiled code is then uploaded into a board containing the
microcontroller, memory and various interface circuits. 7. Errors are then fixed by debugging. 8. You may write your own code and/or incorporate code that has
been written by others (“sketches”).
Prof. Steven S. Saliterman
Integrated Development Environment (IDE)
Editor – To write your code in C (.c) and/or assembly (.a) language. A finished program is called a “sketch.”
Compiler – Turns your code into machine readable instructions or object files (.o). A Linker combines this code with the standard Arduino Libraries, producing a single hex file (.h).
Means to Upload – Transferring the hex file to the Arduino board program memory. This is done via the USB or serial connection with the aid of the bootloader.
Means to Run – Executing the Program Means to Debug – Finding & Correcting Errors
Prof. Steven S. Saliterman
Programs are Written in C and/or Assembly Language
Prof. Steven S. Saliterman
Arduino Bootloader & Firmware
Bootloader is resident code that runs when the board is powered on or reset. It is programmed via the ICSP with a programmer.
This code configures the board and USB port for your subsequent use and programming directly from your computer.
You can instead remove the bootloader to save memory and program directly through the ICSP header.
Prof. Steven S. Saliterman
1. Structures A. Setup & loop B. Control statements C. Syntax D. Arithmetic operators E. Comparison operators F. Bitwise operators G. Compound operators
Arduino Programming Components
2. Variables A. Constants B. Data Types C. Variable Scope D. Qualifiers E. Conversion F. Utilities
3. Functions A. Digital I/O B. Analog I/O C. Due & Zero only D. Advanced I/O E. Time F. Math G. Trigonometry H. Characters I. Random numbers J. Bits and bytes K. External interrupts L. Interrupts M. Communication N. USB
Items in blue will be covered in this lecture, items in red in Arduino Part 2, and green in Arduino Part 3.
Prof. Steven S. Saliterman
1. Structures: Setup() Example
1) Initialize variables
2) Assign pins 3) Runs once, after
powerup or reset.
int buttonPin = 3; void setup() { Serial.begin(9600) ; //serial baud rate pinMode(buttonPin), INPUT); //assign pin 3 to be an input } void loop() { … }
Prof. Steven S. Saliterman
Loop() Example
1. Occurs after setup.
2. Loops consecutively
3. Initialize variables 4. Assign pins 5. Runs once, after
powerup or reset. 6. Variations: if, if-
else; if-else-if
int buttonPin = 3; void setup() { Serial.begin(9600) ; //serial baud rate pinMode(buttonPin), INPUT); //assign 3 to be an input } void loop() { if(digitalRead(buttonPin) == HIGH) Serial.write(‘H’); else serial.write(‘L’); delay(1000); }
Prof. Steven S. Saliterman
Control Statements
Loop Statements For While Do-While
Decision Statements Break and Continue If If-Else, if-else-if Switch-Case
Directional Goto Return
Prof. Steven S. Saliterman
Arrays…
1. The first element is indexed with zero, e.g. a[3] has 3 elements, a[0], a[1], and a[2].
2. Declare as usual, e.g. int a[3], float a[3], and char a[3]. 3. Initialize: int a[3] = {2, 6, 1}. 4. Ok to initialize using a “for” loop. 5. If number of elements is not stated, the initialization will
determine it, e.g. int a[ ] = {2, 6, 1} – elements will be three. 6. Arrays may be multidimensional, e.g. a[3, 5]. 7. Two dimensional (rows and columns) can also be written, e.g.
int M[4] [5] (remember there is a zero row and column). 8. Number of elements may be determined by a variable – in
which case range check first.
Prof. Steven S. Saliterman
“For” Statement (a Loop)…
for (initialization; condition; increment) {program statement(s);} Example – What is the value of the a[49] element? … int a[100]; for (int n = 0; n < 100; n = n + 1) { a[n] = n * 2; } …
Statement Format
Example Code
Prof. Steven S. Saliterman
“While” Statement (a Loop)…
while (expression – a boolean that is true or false) {program statement(s);} Example – What is the value of a[30] element? … int a[100]; int n = 0; while (n < 100) { a[n] = n * 3; n = n + 1; // Could also use “++n” } …
Prof. Steven S. Saliterman
“Do-while” Statement (a Loop)…
do {program statement(s)} while (test condition); Example – What is the value of a[75] element? … int a[100]; int n = 0; do { a[n] = n * 4; n = n + 1; } while n < 100; …
Prof. Steven S. Saliterman
“If” Statement (a Decision)…
if (expression) {program statement(s);} Example – What is the value of n? … int a = 4, n = 0; if a <= 5 { n = n + 50; } …
Prof. Steven S. Saliterman
“If-Else” Statement (a Decision)…
if (expression) {program statement(s);} else {program statement(s)}; Example – What is the value of n? … int a = 10, n = 0; if a <= 5 { n = n + 50; } else { n = n + 25; } …
Prof. Steven S. Saliterman
“Switch – Case” Statement (a Decision…)
switch (expression) { case label1: program statements; break; case label2: program statements; break; default: program statements; break; }
For example: int a; Bool buy; … a = 2; switch (a) { case 1: // if a =1 buy = true; break; case 2: // if a =2 buy = false; break; } …
Prof. Steven S. Saliterman
Syntax
; Used to end a statement { } Enclose statements, keep balanced // Start comment until end of line /* … */ Multi-line comment
#define Assigning a value to a constant name Follows C rules and no semicolon afterwards Use const type variable = value (e.g. const float pi = 3.14) when able instead.
#include To include outside libraries
Prof. Steven S. Saliterman
Arithmetic & Boolean Operators
= assignment operator + addition - subtraction * multiplication / division % modulo
&& and || or ! not
Prof. Steven S. Saliterman
Comparison & Pointer Operators
== equal to != not equal to < less than > greater than <= less than or equal to >= greater than or equal to
* dereference & reference
Prof. Steven S. Saliterman
Bitwise & Compound Operators
& bitwise and | bitwise or ^ bitwise xor ~ bitwise not << bit shift left >> bit shift right
++ increment -- decrement += compound addition -= compound subtraction *= compound multiplication /= compound division %= compound modulo &= compound bitwise and |= compound bitwise or
Prof. Steven S. Saliterman
2. Variables: Constants
1. true | false (typed in lower case) 1. false is defined as zero 2. true is defined as one, or any boolean test of an
integer that is non-zero. 2. Integer constants:
Decimal 123 Binary B11110000 (leading B) Octal 0173 (leading zero) Hexadecimal 0x7B (leading 0x)
Prof. Steven S. Saliterman
4. By default, an integer constant is treated as an int
with the attendant limitations in values. To specify an integer constant with another data type, follow it with a: 'u' or 'U' to force the constant into an unsigned data
format. Example: 33u 'l' or 'L' to force the constant into a long data format.
Example: 100000L ‘ul’ or 'UL' to force the constant into an unsigned long
constant. Example: 32767ul
Prof. Steven S. Saliterman
5. Floating point constants: Constant Evaluates to Also 10.0 10 2.34E5 2.34 * 10^5 234000 67e-5 67.0 * 10^-5 .00067
Prof. Steven S. Saliterman
Data Types
1. boolean (8 bit) - simple logical true/false (1 byte = 8 bits) 2. byte (8 bit) - unsigned number from 0-255 3. char (8 bit) - signed number from -128 to 127. The compiler
will attempt to interpret this data type as a character in some circumstances, which may yield unexpected results
https://learn.sparkfun.com/tutorials/data-types-in-arduino
4. unsigned char (8 bit) - same as ‘byte’; if this is what you’re after, you should use ‘byte’ instead, for reasons of clarity
5. word (16 bit) - unsigned number from 0-65535 (1 word = 2 bytes)
6. unsigned int (16 bit)- the same as ‘word’. Use ‘word’ instead for clarity and brevity.
Prof. Steven S. Saliterman
9. long (32 bit) - signed number from -2,147,483,648 to 2,147,483,647
10. float (32 bit) or double- signed number from -3.4028235E38 to 3.4028235E38. Floating point on the Arduino is not native; the compiler has to jump through hoops to make it work. If you can avoid it, you should.
https://learn.sparkfun.com/tutorials/data-types-in-arduino
7. int (16 bit) - signed number from -32768 to 32767. This is most commonly what you see used for general purpose variables in Arduino example code provided with the IDE.
8. unsigned long (32 bit) - unsigned number from 0-4,294,967,295. The most common usage of this is to store the result of the millis() function, which returns the number of milliseconds the current code has been running.
Prof. Steven S. Saliterman
Conversion
char() - Converts a value to the char data type. byte() - Converts a value to the byte data type. int() - Converts a value to the int data type. word() - Converts a value to the word data type
or creates a word from two bytes. long() - Converts a value to the long data type. float() - Converts a value to the float data type.
Prof. Steven S. Saliterman
Variable Scope & Qualifiers
1. A global variable is one that can be seen by every function in a program. Local variables are only visible to the function in
which they are declared. In the Arduino environment, any variable declared
outside of a function (e.g. setup(), loop(), etc. ), is a global variable.
“For “ loop variables are local. 2. Static - the static keyword is used to create
variables that are visible to only one function.
Prof. Steven S. Saliterman
3. Volatile - a keyword known as a variable qualifier, it is usually used before the datatype of a variable, to modify the way in which the compiler and subsequent program treats the variable. e.g. volatile int state = LOW; Specifically, it directs the compiler to load the variable from
RAM and not from a storage register. A variable should be declared volatile whenever its value
can be changed by something beyond the control of the code section in which it appears, such as a concurrently executing thread.
In the Arduino, the only place that this is likely to occur is in sections of code associated with interrupts, called an interrupt service routine.
Prof. Steven S. Saliterman
Summary
Arduino Uno, sensors and actuator examples.
Using an IDE, programs are typically written in C and assembly language, compiled, linked with libraries and uploaded onto the Arduino board memory as hexadecimal code.
Structures, variables and functions comprise an embedded program.