Department of Bioengineering 

MEng  Engineering Courses

Arduino 1st Year Task sheet

Summer Term, 2021

Syllabus:

•    The uses of Development kits and role in product development.  Standard tools available for

development work, role of Open Source tools.  The marketplace of development system / tools.

•    Alternative technologies to embedded microprocessor based, and relative choices.

•    Programming an embedded processor with a high-level language (C):   A range of commands, program control, developing a clear style.

•    Basic concepts of data flow in an embedded system: Analogue to digital conversion, Digital to Analogue conversion, sensors and transducer.

Learning Outcomes:

At the end of this course, participants will be able to:

•    Code a Sketch in Arduino code, download it into a target board and test it runs

•    Describe the typical uses ofan Arduino

•    Place  the  Arduino  in the marketplace  of available development system, with its relative advantages and disadvantages against other possible solutions

Assessment

This activity forms part of Design and Professional Practise. The intention is you keep a portfolio and demonstrate that you can setup a commercial development environment and use it to write and modify code, and then download it to given hardware.

Introduction and Overview

You should have now received a kit of parts:

•    Arduino (Nano or UNO)

•    Solderless breadboard, if needed, with wires

•    LED, Resistor, Buzzer (possibly not)

All students with a PC should have downloaded Arduino version 1.8.12.  There is a link from the imperial software hub.  Students with an apple device should have downloaded the latest Arduino IDE for Mac. For this task, please download the IDE for the desktop – do not run from the web-based web app.

If you have a Nano, supplied by the college it will have the CH340 USB chip.  Your PC may not have the driver for this device. How to Install CH340 Drivers - learn.sparkfun.com   has a lot of good advice on this topic, and many others to do with Arduino.

You may wish to come back to this task - or take this further (perhaps for a project?).  The activities are mainly of a practical nature. There will be technician and GTA support at prearranged times – if you are unclear of anything please ask – there are no silly questions!

Introduction:

As digital logic has progressed (Moore’s law - if unaware of - google it) the role of small computers has evolved. The Television and computing have, to an extent, converged.  There are increasingly very small computers doing trivial tasks - in a car the door may contain a small computer that reads the up /down buttons and operates the motor accordingly. This has led to a very, very, big market for “micro-controllers” – a whole small computer on a chip

Naming Convention:

“Microprocessor” – the CPU – “central processing unit” of a computer - this might be very large – e.g. Pentium processor clocking at 3GHz with over 1000 pins, or very small, clocking at, say, 1Mhz.

“Micro-Controller” - A single chip computer.  Typically contains the CPU and some memory (non – volatile for the program, volatile for data) and input/ output circuitry etc.  Very small, cheap- pennies.

“SoC” – System on a chip.  Some markets are so large that it is worthwhile to deliver a dedicated integrated circuit just for that functionality.  They typically contain one or more microcontrollers, and some dedicated logic circuitry – perhaps designed in a program like Quartus II.    Examples include televisions, consumer electronics, games, medical devices.

“Open Source” - Some software is released “free” to use.    Typically, the company will aim to make profit from added services, for example technical support.  There is a lot more to this – “free” is a complex term.

“Development board”: To sell a microprocessor chip the chipmaker often designs an example system or “development board”.   This saves the system designer a lot of the design work. Buying the chips allows you to copy elements of the design (care needed for commercial products!).

What is an “Arduino”

Arduino is an “open source” hardware “platform” .  It is a small printed circuit board with components on.  It is also a software program running on a PC (or Mac).   The software is an “IDE” - Integrated Design Environment.  If you want the code to read a temperature sensor, or the code to play a tune – somebody else has already written it and published it (better to give than receive!). The circuit design for the hardware is openly published. The code for the IDE is published. “Open Source” – good and bad.  You may prefer the comfort of being a customer - with commercial liabilities.

See Appendix A for competitors for Arduino – The Arduino sits in a market-place worth billions of dollars of microcontrollers and development kits for microcontrollers.

Ifa “Compiler fell on your toe- would it hurt?”

Arduino calls programs “Sketches” .  The Arduino IDE include a “compiler” .  A complier takes a text file of commands in the chosen high-level language (in this case C) and produces machine code, 1s and 0s of valid instruction for the chosen micro-processer. So, a compiler is a software tool, like Microsoft Office, or Matlab are. Also had an upload function – writing to the hardware.

TASK1:  introduction: Writing your first “Sketch” (program).

BLINK!

a.    Everything between  /* … .  */    is ignored  - it isjust a comment for us humans.

b.    Everything on a line after // is ignored -just a comment

c.    Every command inside {  … . }  becomes like one statement together

d.    Every “sketch” has a setup part (which is only done once) and a loop part which is done repeatedly.

e.    Every command is separated by ;

f.    “Compiling” turns this text file into an executable program for the Arduino (the buttons “compile”

and “upload” are in menu bar  .   (Hover on them!).

g.    “Uploading” sends the executable to the Arduino –which stores it permanently and runs it.

h.    The “IDE” helpfully colour codes- grey for comments etc.

TRY IT!

(Blink is already typed in for you – if you start IDE program open

file/examples/basic/blink)

1.   (Will need to go into tools menu and select which device you have- i.e. Nano or UNO) and possibly which USB port your device is on – typically the highest value e.g. COM9.   See appendix D for more help details.

2.   After compiling and uploading – prove to yourself it is stored in the Arduino.  Unplug it and plug back in again- without downloading again or even opening Arduino IDE- is it still there? Still blinking?

You have written, compiled, downloaded and test a simple program!

3.   Try replacing LED_BUILTIN with 13, does it still work?

4.   Is “digitalWrite” case sensitive? (try it)

5.   Try varying the relative delays for the time on and the time off.  What units are the argument of delay in?

6.   If you have one, connect the buzzer between pin  13 and ground (find it on Arduino – it is labelled).   “Middle C” is 262Hz (i.e. 262 cycles per second).  Can you make a noise / play a tune? / is resolution of delay function fine enough?     Is there a similar function with a finer resolution – e.g. microseconds? (Google?)  (If you do not have a buzzer- an old headphones or a small speaker from an old radio would do instead – else omit this part).

TASK2: Developing “blink” program into Pulse Width modulation – simple example

We have seen we used a “function” called “delay”.   A function is a number of lines of code we can call up as one- like a program within a program.  Typically, it has one or more argument inputs, and may return a value.

There are a large number of pre-written functions (such as delay) – or we can write our own.

The output pins ofthe Arduino are wholly digital – they can output a 0 (=0V) or a 1 (or “high”) = 5V. Often we want not just an on or ff= but a variable (e.g. the speed of a motor- the energy into a heater etc.). Arduino copes with that by use of“Pulse Width Modulation”.

Tasks

Rewrite “blink” so that the output is high for 10% of the time and low for 90% of the time (and the frequency >50Hz). Repeat for 90% high / 10% low. Note brightness of led.

We have just done “pulse width modulation” – the signal –or value – modulations (controls) the width of the pulse.

We want to use the PWM process a lot.  The chip inside the Arduino has some circuitry to do it for us. The IDE gives us a function to call it up (AnalogWrite). Open the program “Fade” which is in the Files\examples\Basic menu.

Notice The function “AnalogWrite” has two arguments. What are they?

a.   Investigate “tone” function.  Write a sketch to play a tune of your choosing. (If have buzzer or speaker)

b.   Investigate “libraries” and the “include” compiler directive.

Task 3: Inputs: Use of “sensors”

We saw in the last task, while the Arduino has no analogue outputs – it has pseudo ones by the use of PWM. To process analogue values the Arduino has six analogue inputs. (Named A0 to A5).

The analogue inputs, by default, return a number between 0 and 1023 – representing between 0V and 5V

Tasks:

1.   Take a wire from pin marked A0 to pin marked 3.3V   Run AnalogSerialRead (in the examples directory). Run the serial monitor (in tools). What value is returned for 3.3V. Move the wire from 3.3V to 5V – should now see 1023- What is (3.3/ 5)*1023? Now move to GND, what do you see?  Leave it dangling - what do you see?

2.  Experiment with serial plotter (if on your version Arduino IDE – not on all).    It is almost like your own oscilloscope – admittedly at very low frequencies!

We can think of almost any microprocessor based system as being some real process (“the real world”) which we measure – with a sensor and an ADC, some processing power, a DAC and then actuator / transducer.   We measure the real world, think about it, and do something about it.   (A classic example is a heating system- the heat output is inversely proportional to the temperature difference between the actual measured temp and the “set point”).

Figure 4

3.  For the following systems – State which is input, output, and what the process going on is?

a.    A Television

b.   A cash machine

c.   A hospital ultrasound scanner

d.   A digital stethoscope

e.   A TENS unit

Other ideas: (All optional -Summer fun!)

1.   Use the circuit in appendix A to control a motor or a light bulb (will need to source a npn transistor and a dc motor – perhaps from a toy?)

2.   If you have potentiometer available connect its ends between 3.3V and GND.  Then the wiper will be a variable voltage.  Read it (using analogRead) and change value of tone.   (Careful – the input is 10bit (0->1023) the output is 8 bit (0->255).

3.   Investigate “map” function.

4.   Go back on a circuit you made elsewhere – e.g. stethoscope or digital logic tasks.  See if can do it with an Arduino and in software - which is better?

5.   Install a frequency measuring app on a phone - and look at spectrum of the output of tone.

6.   Get a BLE (Bluetooth Low Energy module) and pair it with a mobile device.

7.   Use “Tone” at very low frequency” and feedback toA0 (Analog in). Watch with Serial plotter. Investigate code for “low pass frequency filtering”, effect on wave form.  (Actually, a simple low pass filter can be a “running average” -e.g. the average of the last 3 samples- can implement with 3 variables – or better an “array” and a “pointer”).

Appendix A: Competitors to Arduino:

Using the Arduino is one way to develop a digital system. If the system is to be in relatively high cost, small numbers it is possible that an Arduino could be in the final product sold.  Alternatively, the circuitry from theArduino can be copied (ithas a main microcontroller from Atmel), and amalgamated with  any  add-on  ICs  to  make  a  final  circuit.  In  that  case,  we  are  using  the  Arduino  only  for development purposes- it is our “development platform” . Most micro controller IC makers have for sale development platforms to facilitate designing in their IC into your products.  Suppliers like NXP, Freescale, ST all sell ICs based upon the ARM micro-processor and have a range of development platform. Texas Instruments (ti) have their “Launchpad” range which are similar to Arduino – but higher cost, greater functionality, and a little less accessible to get started.

Raspberry Pi:

This is based upon a Broadcom ARM processor (the type that might be found in a tablet). It is low cost. It is nearer a PC – for example it has a socket to plug a monitor in, and a USB host socket.  It is aimed at the hobbyist market, similar to Arduino – but higher cost, higher functionality.  It is perhaps more accessible – it run lynux and presents similar to a PC type desktop.   Coding tools for a range of users have been developed – including children.

PIC

Prior to Arduino the major IC for small simple / hobbyist embedded systems were the PIC family. Very low cost development board are available – and so much functionality is on the chip it takes very little extras to make a system. Often PICs were programmed in assembler language –which is more like the machine code – but C compiler are available.  The PIC family has a wide range- from very simple in 8 pin packages, to complex ones with a lot of input/ output including USB, complex processors, and many extra blocks.

FPGA:

“Field Programmable Gate Arrays” are ICs with arrays of NAND gates and flip / flops /timers etc. They come “uncommitted”.  There is programmable interconnection between the gate and timers etc. We can program in combinatorial and sequential logic functions into them, using a development system such as Quartus II.   (Quartus is the compiler, which takes the designed logic relationship and translates it into which fuses to blow or leave intact to interconnect to give that functionality). One can buy low cost development boards.

It is not unusual for a new design –for example in a printer- to go into production with the design on an FPGA and after many 10s of thousands sold for the design to be moved to a dedicate SoC (system on chip).

PC:

For complex systems it is not unusual to use a PC board in an embedded system.  For example many tills and medical devices are actually PCs – in a smaller size called PC104.  This reduces development costs- but increases unit costs (but many start-ups are short on capital – but intend a high margin).

Appendix B: Controlling Real things (optional)

The Arduino has outputspins that are set to be 0V or 5V.   They are not designed to provide significant energy.    (If we present a load of 1k Ohms to ground then 5mA will flow out- good engineering suggests do not exceed this by much- but pins are actually rated a little higher).    We  can use  a transistor as a switch, to “buffer” the pins.  Below is a BJT (bipolar junction transistor) version of the circuit.

1.   Build this circuit on breadboard and modify your code so that the motor toggles every 2s between two distinct speeds. (May need to use a different generic npn BJT). The lab has numerous –look at marking, i.e. the number and find its “pinout” online.

2.   Research “flywheel diode” and thus explain its use in the circuit below.

Appendix C: Problems with Wearables and Arduino / BLE

1.   Many devices which are intended to be “wearable” come across body fluids/ sweat etc -liquids and electronics do not mix well.

2.   There  are  mechanical issues with making a rigid PCB and battery conform to a moving biological surface.     There are particular problems with  any wire connections / typically soldered.  Conductive thread is sometimes used — perhaps better to have no wires?

3.   Flexible PCBs are possible — maybe a more suitable technique for a wearable?

4.   The Arduino is not optimised for low power (in a wearable power consumption is critical) other very low power devices optimised for battery usage are available

5.   If Arduino is used — it is probably best to use one with BLE (Bluetooth Low Energy) built in.