MediaLab_EncapsulationExp - Design Report

Encapsulation Experiment
Design Report
Rev. 12 — March 21, 2016 Biomechatronics Group
Document information
Info Content
Keywords Encapsulation, Arduino, Schematics, PCB, Layout, Firmware,
CSV, DAC, Mux
Abstract TBD
Author Valérian Geny
Revision history
Rev Date Description
Draft 1 2016 February 15 Document creation
Rev 1.0 2016 February 20 First prototype
Rev 1.1
draft 1
2016 February 24 Second prototype
Rev 2 2016 March 6 Added RTC Clock

Biomechatronics Group
MIT Media Lab Encapsulation Experiment
Design Report
System Testbench All information provided in this document is subject to legal
disclaimers.
MIT B.V. 2013. All rights reserved.
Design Document Rev. 12 — March 21, 2016 2 of 32
Table of Content
Table of Content.............................................................................................................................................2
Table of Figures .............................................................................................................................................3
1. Document Purpose...........................................................................................................................4
2. Glossary ............................................................................................................................................5
3. Requirements: ..................................................................................................................................6
3.1 Purpose...........................................................................................................................................6
3.2 Components Under Test .................................................................................................................6
3.3 Actors and Use Cases.....................................................................................................................6
3.4 Requirements..................................................................................................................................7
4. Components......................................................................................................................................8
4.1 Microcontroller: Arduino Uno...........................................................................................................8
4.2 Logging Module: SparkFun microSD Shield....................................................................................8
4.3 Real Time Clock (RTC): DS1307.....................................................................................................9
4.4 Digital to Analog Converter (DAC): MCP4725.................................................................................9
4.5 Multiplexer: CD74HC4067.............................................................................................................11
5. Schematics and Layout..................................................................................................................12
5.1 Functional Bloc Diagram ...............................................................................................................12
5.2 Microcontroller Pin Allocation ........................................................................................................12
5.2.1 Pin usage ......................................................................................................................................12
5.2.2 Pin Mapping ..................................................................................................................................12
5.3 Schematics....................................................................................................................................13
5.3.1 Board.............................................................................................................................................14
5.3.2 Components Under Test (CUT).....................................................................................................15
5.4 PCB and Layout ............................................................................................................................16
5.5 Bill of Material................................................................................................................................18
5.6 Realization.....................................................................................................................................18
5.6.1 Prototype V1.0...............................................................................................................................18
5.6.2 Prototype V1.1...............................................................................................................................18
5.6.3 Components Under Test (CUT).....................................................................................................18
6. Firmware..........................................................................................................................................20
6.1 Arduino Integrated Development Environment (IDE).....................................................................20
6.2 Pin Mapping ..................................................................................................................................20
6.3 Libraries.........................................................................................................................................20
6.4 Procedures and Functions.............................................................................................................21
6.4.1 Setup / Loop..................................................................................................................................21
6.4.2 RunDacTest ..................................................................................................................................21
6.4.3 RunMuxTest ..................................................................................................................................21
6.4.4 Leds...............................................................................................................................................22
6.5 Reset Counter ...............................................................................................................................22
6.6 Real Time Clock ............................................................................................................................22
7. Log files...........................................................................................................................................23
7.1 Formatting .....................................................................................................................................23
7.2 Logged data ..................................................................................................................................23
8. Bibliography....................................................................................................................................26
9. Annexes...........................................................................................................................................27

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Table of Figures
Figure 1: Requirement map representation......................................................................................................7
Figure 2: Arduino Uno board (from SparkFun).................................................................................................8
Figure 3: Sparkfun Micro SD Shield.................................................................................................................9
Figure 4: DS1307 Real Time Clock breakout board.........................................................................................9
Figure 5: SparkFun I2C DAC Breakout - MCP4725.......................................................................................10
Figure 6: SparkFun Analog/Digital MUX Breakout - CD74HC4067................................................................11
Figure 7: Board Schematic.............................................................................................................................14
Figure 8: DAC Wiring .....................................................................................................................................15
Figure 9: MUX Wiring.....................................................................................................................................16
Figure 10: 3D Model (left: Top, right: Bottom)...............................................................................................16
Figure 11: Layout (left: Top, right: Bottom).....................................................................................................17
Figure 12: Assembling Instructions (left: Top, right: Bottom)..........................................................................17
Figure 13: First prototype...............................................................................................................................18
Figure 14: Encapsulated DAC (Sparkfun breakout board).............................................................................19
Figure 15: Arduino IDE screen capture..........................................................................................................20
Figure 16: CSV Log file opened with Excel (Screen capture) ........................................................................23

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1. 0BDocument Purpose
This document describes the system performing the Encapsulation Experiment. Its main purpose is
to facilitate the comprehension of the system and to allow the reader to understand the technical
environment. It also intends to be a technical reference document for any person who would be in
charge of maintaining, improving, or extending this experiment.

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2. 1BGlossary
ADC: Analog to Digital Converter
CSV: Comma Separated Values
CUT: Chip Under Test
DAC: Digital to Analog Converter
EEPROM: Electrically Erasable Programmable Read-Only Memory
FW: Firmware
GND: Ground
HW: Hardware
I/O: Input / Output
I2C: Inter-Integrated Circuit
IDE: Integrated Development Environment
LED: Light-Emitting Diode
MIT: Massachusetts Institute of Technology
MUX: MUltipleXeur
PCB: Printed Circuit Board
PWM: Pulse Width Modulation
RTC: Real Time Clock
SCL: Serial Clock Line
SD: Secure Digital
SDA: Serial Data Line
TBD: To Be Defined
TWI: Two Wire Interface

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3. 2BRequirements:
3.1 9BPurpose
This experiment intends to determine the life expectancy of different encapsulation methods.
Components Under Test (CUT) will be immerged in a saline solution for certain time durations (from
months up to years). The system shall check daily if the CUTs are still functioning, and to retrieve
metrics on the changes due to aging
3.2 10BComponents Under Test
This experiment intends to test the following components:
• Digital to Analog Converter (DAC): MCP4725
• Multiplexer (MUX): CD74HC4067
More components might be added in future experiments
3.3 11BActors and Use Cases
TBD

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3.4 12BRequirements
Figure 1: Requirement map representation
Test Component life
expectancy
Test
Encapsulation
Methods
Mesure time
Test each
component daily Generate
commands or input
signal
Retrive Analog
output signal
Compare with
expected value
Reduce cost and
complexity
Compute a status
and some metrics
A board should test
more than one
component
PCB shall be
scalable
Test Component
Use Arduino boards
Display and log
Results
Use Leds to
provide a Status
Log data on a SD
Card
Provide a tool for
deep analyse
Recover from power
shutdown

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4. 3BComponents
This section provides a brief description of the components/PCB used by the system. For more
details, please refer to the links provided.
4.1 13BMicrocontroller: Arduino Uno
 https://www.arduino.cc/en/Main/ArduinoBoardUno
 https://www.sparkfun.com/products/11021
Figure 2: Arduino Uno board (from SparkFun)
Features:
• ATmega328 microcontroller
• Input voltage - 7-12V
• 14 Digital I/O Pins (6 PWM outputs)
• 6 Analog Inputs
• 32k Flash Memory
• 16Mhz Clock Speed
4.2 14BLogging Module: SparkFun microSD Shield

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Figure 3: Sparkfun Micro SD Shield
4.3 15BReal Time Clock (RTC): DS1307
 https://www.adafruit.com/product/264
Figure 4: DS1307 Real Time Clock breakout board
SQW pin is not used and doesn’t have to be connected.
Features:
• Two wire I2C interface (0x68 Address)
• Hour : Minutes : Seconds AM/PM Day Month, Date - Year
• Leap year compensation
• Accurate calendar up to year 2100
• Battery backup included
• 1Hz output pin
• 56 Bytes of Non-volatile memory available to user
4.4 16BDigital to Analog Converter (DAC): MCP4725

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Figure 5: SparkFun I2C DAC Breakout - MCP4725
Features:
• 12-bit resolution
• I2C Interface (Standard, Fast, and High-Speed supported)
• Small package
• 2.7V to 5.5V supply
• Internal EEPROM to store settings
Schematics
The ATmega328 microcontroller uses the I2C (also called TWI) to send controls to MCP 4725
DAC. Consequently, each DAC must have a different address.
I2C Addresses (solder jumper):
• 0x60 to 0x61 (SparkFun)
• 0x62 to 0x63 (AdaFruit)

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4.5 17BMultiplexer: CD74HC4067
 http://www.win.tue.nl/pinpasjc/docs/apis/offcard/com/ibm/jc/tools/JCShell.html
Figure 6: SparkFun Analog/Digital MUX Breakout - CD74HC4067
Features
• 16 channels
• 2V to 6V operation
• “On” resistance: 70 Ohms @ 4.5V
• 6ns break-before-make @ 4.5V
Schematics

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5. 4BSchematics and Layout
5.1 18BFunctional Bloc Diagram
TBD
5.2 19BMicrocontroller Pin Allocation
5.2.1 32BPin usage
Required pin
per DAC
Required pin per
MUX
LED SD Card Serial
Com
Total
Available
on
Arduino
Uno
Analog
Pins
2 (I2C) +
nDac *1
nMux *1 0 0 0 6
Digital Pins 0 4 (SelectChanel)
+ 1 *nMux
(Optional Enable)
nLED*1 4 2 14
Exemple: 2 MUX + 2 DACS + 4 LEDs
• Analog Pins = ((2 * I2C) + 2 * nDac)+ (2 * nMux) = 6
• Digital Pins = (0 * nDac) + (4 + 0 * nMux) + (1* nLED)+ (4) + (2) = 14
5.2.2 33BPin Mapping
Analog Pins 2 MUX + 2DAC 4 DACS 6 MUX 3 MUX + 1 DAC
A0 MUX 0 (SIG) DAC 0 (Analog) MUX 0 (SIG) MUX 0 (SIG)
A1 MUX 1 (SIG) DAC 1 (Analog) MUX 1 (SIG) MUX 1 (SIG)
A2 DAC 0 (Analog) DAC 2 (Analog) MUX 2 (SIG) MUX 2 (SIG)
A3 DAC 1 (Analog) DAC 3 (Analog) MUX 3 (SIG) DAC 0 (Analog)
A4 /SDA I2C (SDA) I2C (SDA) MUX 4 (SIG) I2C (SDA)
A5 / SCL I2C (SCL) I2C (SCL) MUX 5 (SIG) I2C (SCL)
Digital Pins 2 MUX + 2DAC 4 DACS 6 MUX 3 MUX + 1 DAC
D0-D1 Serial Communication with the Development PC (TX/RX)

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D2 – D5 Status LEDs
D6-D7 S0 – S1 NA S0 – S1 S0 – S1
D8 SD Card Data Logger (SS )
D9-D10 S2 – S3 NA S2 – S3 S2 – S3
D11-D13 SD Card Data Logger (MOSI, MISO and SCK )
5.3 20BSchematics
The schematic and the board layout were designed with CadSoft Eagle.
 http://www.cadsoftusa.com/

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5.3.1 34BBoard
Figure 7: Board Schematic

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5.3.2 35BComponents Under Test (CUT)
Figure 8: DAC Wiring

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Figure 9: MUX Wiring
5.4 21BPCB and Layout
Figure 10: 3D Model (left: Top, right: Bottom)

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Figure 11: Layout (left: Top, right: Bottom)
Figure 12: Assembling Instructions (left: Top, right: Bottom)

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5.5 22BBill of Material
TBD
5.6 23BRealization
5.6.1 36BPrototype V1.0
Prototype V1.0 is designed, wired and programmed to work with the following components:
• MUX_0 (on A0)
• MUX_1 (on A1)
• DAC_2 (on A2)
• DAC_3 (on A3)
• I2C: SCL (on A4)
• I2C: SDA (on A5)
For prototype V1.1 and under, the RTC is mounted on the Sparkfun Micro SD Shield prototyping
area. The 4 pins GND, 5V, SDA, SCL are respectively connected to the Micro SD Shield pins
GND, 5V, A4 and A5.
Unrouted wires on the PCB might be needed for specific configurations
Figure 13: First prototype
5.6.2 37BPrototype V1.1
Prototype V1.1 hasn’t been mounted yet.
5.6.3 38BComponents Under Test (CUT)
I2C bus requires two 4.7k pull-up resistors on SCL and SDA lines. These resistors are usually
mounted on each Sparkfun Breakout boards. To avoid multiple resistors on the SCL/SDA bus lines,

Design Report
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you must disable these resistors on the Sparkfun boards if they are already mounted somewhere else
(i.e. on the RTC).
Each I2C chip connected to the bus must have a different address. Addresses can be modified by a
physical modification on the Sparkfun breakout PCB (solder jumper)
Each Component Under Test must have a different output line. When wiring these components,
please refer to section TBD to assign them a different pin on the connectors.
Each MUX has a different Enable (EN) pin mapping on the MUX Connector. As of today, Enable
pins are not used and tighten to GND.
Do not leave unused input pins unconnected when encapsulating, except if they have a pull-
up/down resistor.
Figure 14: Encapsulated DAC (Sparkfun breakout board)

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6. 5BFirmware
6.1 24BArduino Integrated Development Environment (IDE)
 https://www.arduino.cc/en/Main/Software
Arduino IDE is a lightweight and very simple Integrated Development Environment for Arduino
Boards. It includes all the required tools to write, compile, upload and run a program on an Atmel
microcontroller.
Figure 15: Arduino IDE screen capture
Arduino IDE does not require any external program to upload the program to the microcontroler.
6.2 25BPin Mapping
Pin Mapping is entirely defined at the beginning of the Sketch. It can be easily modified if required.
Please refer to section 5.2.2 for the exact pin mapping.
6.3 26BLibraries
We use the following libraries, provided by Arduino or AdaFruit
• SPI.h:
Provides functions to communicate with an external chip through the SPI protocol
• SD.h: SparkFun MicroSd Shield
Provides dedicated functions to read/write files on the SD card
• Wire.h: I2C / TWI library
Provides functions to communicate with an external chip through the I2C/TWI protocol

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• Adafruit_MCP4725.h: MCP4725 Digital to Analog Converter (DAC) library
Provides dedicated functions to send commands to the DACs (through I2C)
• EEPROM.h: Microcontroller non-volatile memory
Enables the reading/writing of the Reset counter value in the non -volatile memory
• RTClib.h: Real Time Clock library
Provides dedicated functions to get the date and time from the RTC (through I2C).
6.4 27BProcedures and Functions
6.4.1 39BSetup / Loop
There are two special functions that are a part of every Arduino sketch: setup() and loop(). The
setup() is called once, when the sketch starts. It's a good place to do setup tasks like setting pin
modes or initializing libraries. The loop() function is called over and over and is heart of most
sketches. You need to include both functions in your sketch, even if you don't need them for
anything.
6.4.2 40BRunDacTest
This function is performing the following actions:
• Write data into the log file (Experiment #, date, Device Id)
• Send 2*4096 commands to the DAC to generate a triangle waveform
o Send commands
o Retrieve Analog output
o Compute error
• Compute and save statistics into the SD card
6.4.3 41BRunMuxTest
This function is performing the following actions:
• Initialise communication with Dev. PC (Serial Link TX/RX)
• Setup I/O
• Read the EEPROM and increase the reset counter.
• Initialize communication with Sparkfun SD Card Shield (SPI)
• Initialize Initialize communication with the DACs (I2C)
Loop()
• For each DAC: Run Tests and Log results
• For each MUX: Run Tests and Log results
• Wait
Select
Channel
(S0..S3)
Retrieve
Voltage
(Analog pin)
Compare
with
Expected
Value
Log the
value
If Error > Threshold
- Print msg on Serial Link
- Switch On the Error Led
Send a
command
to generate
a Waveform
Retrieve
Voltage
(Analog pin)
Compare
with
Expected
Value
Log the
relative and
absolute
Error
If Error > Threshold
- Print msg on Serial Link
- Switch On the Error Led
RunDacTest(...) RunMuxTest(...)

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• Write data into the log file (Experiment #, date, Device Id)
• Send commands to the DAC to generate a triangle waveform
o Set [S0..S3] bits to select the appropriate channel
o Retrieve Signal analog value
o Save Signal analog value into the SD card
o Compute error
• Compute and save statistics into the SD card
6.4.4 42BLeds
The following table provides a description of the Leds meaning.
Behavior Explanation
One Led is red Corresponding component is
failing.
One Led is periodically red for
a short time
One or several channels of the
corresponding component
returns incorrect values
All the Leds are blinking Unable to initialize the SD Card.
Experiment didn’t start
All the Leds are red Unable to write on the SD Card
6.5 28BReset Counter
After each reset, the program will read the reset counter located at address 0 of the EEPROM (non
volatile memory) and increase it by one.
To clear the EEPROM and reset this counter, use the dedicated sketch program ‘clearEEPROM.ino’
You can also reset the counter by removing the RTC battery.
6.6 29BReal Time Clock
If the RTC isn’t already running, the following instruction will set the time and the date to the
compilation time.
RTC.adjust(DateTime(__DATE__, __TIME__));

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7. 6BLog files
7.1 30BFormatting
All data is stored on the SD Card. The files are encoded using the Comma Separated Values (CSV)
file format. The delimiter is the semi-colon (;).
Files are named as follow:
• [Reset counter]_[Component identificator].csv
The Component identificators are:
• M: Multiplexer (MUX)
• D: Digital to Analog Converter (DAC)
Figure 16: CSV Log file opened with Excel (Screen capture)
To convert a CSV file into an Excel spreadsheet, use the Excel feature “Text to Columns” in the
Data Tab.
7.2 31BLogged data
For the MUX, the following colums are used:
Column Name Description Unit/Range
Experience Restarts after each reset [1-∞]

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Number
Date
Date and time using the following format (YYYY/MM/DD –
HH:mm)
-
DeviceId Device identifier [0-5]
InputC0 ..
InputC14
Voltage measurements for each of the used MUX channels Volts (V)
Error
Cummulative error mean on the up side of the triangle waveform
𝐸𝑟𝑟𝑜𝑟 =
∑ 𝑖𝑛𝑝𝑢𝑡𝐶𝑖
𝐼𝑛𝑝𝑢𝑡𝐶14
8
Volts (V)
Error Abs
Cummulative absolute error mean on the up side of the triangle
waveform
𝐸𝑟𝑟𝑜𝑟𝐴𝑏𝑠 =
∑ |𝑖𝑛𝑝𝑢𝑡𝐶𝑖 |𝐼𝑛𝑝𝑢𝑡𝐶14
8
Volts (V)
Status
Boolean indicator
• 0: No problem detected, analog values are in the
acceptable range
• 1: Problem detected retrieved analog values are out of
the
[0/1]
For the DAC, the following colums are used:
Column Name Description Unit
Experience
Number
Restarts after each reset [1-∞]
Date
Date and time using the following format (YYYY/MM/DD –
HH:mm)
-
DeviceId DAC identifier [0-5]
V0+ to V3+
Specific voltage measurements on the up side of the triangle
waveform.
Volts (V)
V3- to V0-
Specific voltage measurements on the down side of the triangle
waveform.
Volts (V)
Error Up
Cummulative error mean on the up side of the triangle waveform
∑ 𝑉𝑎𝑛𝑎𝑙𝑜𝑔
4095
0
4096
Volts (V)
Error Up Abs
Cummulative absolute error mean on the up side of the triangle
waveform
∑ �𝑉𝑎𝑛𝑎𝑙𝑜𝑔�4095
0
4096
Volts (V)
Error Down
Cummulative error mean on the down side of the triangle
waveform
∑ 𝑉𝑎𝑛𝑎𝑙𝑜𝑔
0
4095
4096
Volts (V)
Error Down Abs
Cummulative absolute error mean on the down side of the
triangle waveform
∑ �𝑉𝑎𝑛𝑎𝑙𝑜𝑔�0
4095
4096
Volts (V)

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Status
Boolean indicator
• 0: No problem detected, analog values are in the
acceptable range
• 1: Problem detected retrieved analog values are out of
the
[0/1]

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8. 7BBibliography
 https://www.arduino.cc/en/Main/ArduinoBoardUno
 https://www.adafruit.com/product/264
 http://www.win.tue.nl/pinpasjc/docs/apis/offcard/com/ibm/jc/tools/JCShell.html
 http://www.cadsoftusa.com/
 https://www.arduino.cc/en/Main/Software

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