SAP-1 ARCHITECTURE

I stumbled upon the idea of a SAP (simple as possible) breadboard computer while surfing Youtube one day and thought it would be a great idea to replicate the computer myself and improve upon the initial design. The computer is composed of 13 independent modules and can be programmed with basic machine language using the RAM dip switches to do simple math. Through this project, I learnt:

1. Computer architecure
2. Digital circuit design
3. Flip-flops, latches, logic-gates, clocks, EEPROMs, RAMs
4. B.O.M management, project timeline, cost-effective design strategies

• Timeline: December 2017 - February 2018                       ‌
• Category: Digital design, Computer architecture, ASIC

VISION BOT

The primary objective of this project was to create an RC tank employing a PS3 controller, capable of providing live video streaming in order to monitor the entire home from a stationary base. I quickly realized however, that instead of using a seperate controller and a secondary device (such as tablet) for video feedback from the Pi camera, it would be economical to control the tank via just the tablet. The tank chassis motors are controlled with L293h IC and the pan & tilt servos are controlled and powered via GPIOs. Through this project, I learnt:

1. Creating custom PCBs using Eagle CAD
2. About Raspberry Pi and it's versatility
3. Designing mechanical parts in SolidWorks and error of margin
4. Python, HTML, CSS, Javascript, AJAX, Bash scripts, Linux libraries

• Timeline: February 2018 - March 2018          ‌
• Category: Robotics, System design, Motors

WIFI AC SWITCH

This project was created with the intentions of aiding a physically disabled person. The relay box can simply be plugged into the AC wall socket and any appliance can then be connected to one of the four channels and be controlled online via web UI. The four channel relay board has an onboard Darlington transistor array so it can be triggered directly from the GPIO of the ESP8266 µController. Through this project, I learnt:

1. HTML, CSS, AJAX, Javascript, C++
2. About the ESP8266 which is a cheap, Wifi enabled microcontroller
3. Modeling parts in SolidWorks and creating an assembly to ensure design feasibility

• Timeline: April 2018 - April 2018                                                              ‌
• Category: Digital design, Home automation, Web UI development

CNC PEN PLOTTER

In order to recycle discarded PCs in a creative way, I decided to design and create the pen plotter. The X and Y axis stepper motors came from the DVD drives in the CPU and I found the plexi-glass surface from a previously used fixture. Each stepper motor is controlled via an L293D IC and the servo motor is connected directly to the µController's GPIO. Through this project, I learnt:

1. to Create custom PCBs using Eagle CAD
2. Arduino C++ and Processing GUI for Arduino
3. Design mechanical parts in SolidWorks and error of margin

• Timeline: May 2018 - June 2018                     ‌
• Category: Robotics, System design, Motors

PDG TOOL

The testers created at Celestica append a Parametric log sheet sheet at the end of each run which contains the names of various tests and the values obtained per UUT. Customers sometime demand for a graphical representation of each test parameter which is tedious to deliver. Therefore, I was assigned with the task of creating a stand-alone processing tool which would take in the paramteric .CSV file and graph the user specified parameter. Through this project, I learnt:

1. to Create a LabVIEW windows application
2. Software documentation and comments format as per the industry standard

• Timeline: May 2018 - July 2018                ‌
• Category: Automation, Software design

EMAIL PARSER

An important part of project management is to keep track of daily purchases with various vendors accurately. Since all the purchases I made at Celestica were through e-mail, I created an email parser to scan the inbox regularily for unread emails. Depeneding on the PO number mentioned in subject line, it would then parse the email date, body, subject and sender's email ID into a google spreadhseet in which each vendor had their own worksheet. Through this project, I learnt:

1. Object oriented and modular programming
2. Working with Google Drive and Sheets API

• Timeline: June 2018 - August 2018                                       ‌
• Category: Automation, Scripting, Software engineering

SECOND ORDER PLL

Phase locked loops are widely used to synchronize and synthesize frequencies in microelctronics. The above image is the open-loop response of a 10 MHz PLL designed as per the requirements of laboratory 2 for ELE 724 (CMOS Mixed-Mode Circuits) using TSMC 130nm technology in Cadence. A typical second order, 4 stage PLL consists of (1) Voltage Controlled Oscillator (2) Phase-Frequency Detector (3) Charge Pump and a (4) Loop Filter. The PFD detects the phase difference in between the reference voltage and sends an UP/DOWN signal to the CP accordingly. The CP, depending on the output of PFD, either sources or sinks the Control Voltage of the VCO which in turn decreases or increases the frequency of VCO output. Therefore, a PLL locks on to the phase of the input, not the frequency!

• If UP = DOWN, Control Voltage = NC, VCO output frequency = NC                                                      
• UP > DOWN, Control Votlage increases, VCO output frequency decreases                                      
• UP < DOWN, Control Votlage decreases, VCO output frequency increases                                          

• Timeline: October 2018 - November 2018 ‌
• Category: Analog design                              

4 BIT SAR ADC

A 4 bit SAR ADC was designed as per the requirements of laboratory 3 for ELE724 (CMOS Mixed-Mode Circuits) using TSMC 130nm technology in Cadence. 4 blocks: Sample/Hold circuit, Comparator, Successive Approximation Logic and Digital to Analog converter were independently designed and integrated to form the SAR ADC. The S/H block samples the input voltage when CLK = 1 and holds the voltage level when CLK = 0. The comparator compares the S/H output with DAC output. If S/H output > DAC output, the Comparator output = 1. The Comparator output is fed into the SAR logic which then generates the corresponding analog output of the input voltage. The analog bits are then fed into the charge scaling DAC which then outputs the voltage equivalent to input voltage. The figure above shows the input voltage and the respective output voltage generated by the SAR ADC. The simulation was run for 1.2 ms (transient analysis) in Cadence Virtuoso Analog Environment and took approximately 3 hours to execute.

• Timeline: November 2018 - December 2018 ‌
• Category: Mixed mode design                          

MEDIA CENTER

A media center was designed and implemented on MCB1700 (LPC1768 development board) as a part of the final project for COE718 (Embedded System Design). The media center consists of three main applications: 1 game, MP3 player and a photo gallery. The image above is a snapshot of the game developed. The following peripherals were utilised in the project:

1. LCD
2. LEDs
3. Joystick
4. Potentiometer
5. Speaker
6. USB

All peripheral libraries were provided by the vendor. An interrrupt based approach was used to implement the system instead of using the RTX RTOS in order to gain bonus marks.

• Timeline: November 2018 - December 2018 ‌
• Category: Embedded System Design