Dec 8, 2019
My Senior Design Project
In the Electrical and Computer Engineering program at N.C. State, there is a requisite two-semester “Senior Design Project” class, ECE484 (first semseter) and ECE485 (second semester).
During the first semester of the course (ECE484), projects are presented to students by various university and corporate sponsors; students must select a project to work on and design (in teams), from the ground up, a detailed and thorough solution to the problem statement. Additionally they must make serious steps towards the construction of a working and demonstrable prototype to present to the course instructors, sponsors, and the public. Emphasis is placed on maintaining open and regular communication with the project sponsor, taking meeting minutes as necessary and drafting verbose and exact project requirements, implementation strategies, and near- (<2 weeks) and far-future (>2 weeks) goals to achieve.
During the second semester (ECE485), students must improve on the prototype constructed during the first semester and revise project goals and requirements, adjusting stretch-goals and core requirements to fit sponsor expectations weighed against the realization of the first-term prototype, perhaps shifting some goals (with the sponsor’s consent) to become stretch-goals, deciding which areas and aspects of the project need the most attention most immediately. The goal of ECE485 is to produce a fully-functioning demonstration which meets all of the core requirements laid out in ECE484; this will involve heavy modification of the prototype and further communication with the sponsor.
Emphasis in ECE485 is placed on week-by-week goal-setting and accomplishment, project management, and regular presentations by teams to the course instructors (emulating corporate presentations to a managerial staff) wherein short-term progress, recent problems, and long-term progress towards the construction of the final product is organized and summarized in a format fitting a short presentation with a small, invested audience. Projects are presented by the teams at the end of the semester at the McKimmon center to sponsors, course instructors, and the public at large.
For those teams backed by a corporate sponsor, some effort is also spent by the students to hand-off projects in a secure and timely manner to the people in the sponsor’s company who will be continuing the project.
My team was sponsored by a corporate sponsor (and I am not exactly at leisure to say which one); ultimately I enjoyed the freedom that working with a non-University sponsor gives. I understand that some teams sponsored by the University had core requirements added and removed at the will of their sponsors, largely graduate students and tenured professors and researchers, and were forced to work around that added pressure.
Here is an excerpt from our core requirements document, established very early in the first semester:
The goal of this project is to develop a tool that will automate the sequencing of a mobile device through a series of pre-configured, interactions with the device to simulate a human operator. To achieve this goal, the final system should be able to fulfill the following requirements list. 1. General Operation Requirements and Features: REQ-1.1: The sequencer shall have the ability to simulate operator physical actions, activating the touch screen (touch), side keys, home keys, and/or soft keys. REQ-1.2: The sequencer shall have the capability to receive images from the device screen as part of the sequencing feedback. REQ-1.3: The sequencer shall perform a fixed sequence of steps for a specific make, model, or function. REQ-1.4: The sequencer shall be able to store multiple make, model, or function sequences. Initially, sequences for new device set up of a Samsung Galaxy S8 and iPhone 7Plus will be included. Other sequences may be added later on. REQ-1.5: The sequencer shall have an operator interface to configure, select jobs, start/stop operation, and provide status and error information to the operator. REQ-1.6: The sequencer shall be able to run continuously for at least 20 hours each day. REQ-1.7: The sequencer shall be as compact as possible. The device fixture and mechanism should be able to fit on a 2'x3' workbench alongside existing work area. The controller components may be housed in a separate enclosure. REQ-1.8: The sequencer shall not leave the work station after installation. 2. System/Device/Unit Constraint requirements: REQ-2.1: The sequencer shall be configurable to handle a variety of OEMs and Models. Initially, only the Samsung Galaxy S8 and iPhone 7Plus will be supported. Other device models may be added later on. REQ-2.2: The sequencer shall only need to support handheld smartphones. Tablets are not required to be processed. REQ-2.3: The sequencer shall cost around $5000 in parts to manufacture. REQ-2.4: The sequencer shall be housed in a safe enclosure in order to protect the user from a mechanical/electrical hazard. 3. Other Needs: REQ-3.1: The sequencer shall not interact directly with a workstation, but may display information on a webpage. REQ-3.2: The sequencer shall have labels on any buttons on the sequencer. 4. Optional Features: REQ-4.1: The sequencer may be capable of voice interaction with the device. REQ-4.2: The sequencer may have a web interface or built-in interface which allows for uploading instructions / downloading statistics. REQ-4.3: The sequencer may include an emergency stop button REQ-4.4: The sequencer may require a fixture to hold the device REQ-4.5: The sequencer shall have a configuration mode that will allow the setup and calibration of a new make, model, or function sequence.
Laying out these detailed project requirements, we were able to generate over 40+ individual prototype sketches; we used these sketches as inspiration when choosing a final design. The sketches we generated look similar to the ones below:
… our prototype began to emerge organically from the designs we generated; we began physical construction (selecting a style similar to the second of the above sketches), first with a cardboard mock-up and second with a static, aluminium chassis. It is the aluminium chassis which we used as the chassis to construct our first- and second-semester deliverable products.
Over time, we naturally separated ourselves into our distinct roles without much designation; luckily we each seemed to find a niche becoming of our skillsets. I became the team-lead, responsible for goal-setting, management, and accountability; additionally and since I had the most Linux programming experience I gradually became the lead programmer for the actual sequencer; consequently I had to quickly train myself in computer vision and motor controller programming in order to realize our prototype.
Specifications like the ones above were distributed to the team and helped to keep us focused and on-track to achieve the final product. Below is the aluminium chassis which was completed during 484:
My Role and Design Choices
As lead-programmer, I was responsible for programming the computer-vision and all GPIOs coming from the microcontroller (e.g. stepper-motor control lines, servo-motor control lines) we settled on, the Raspberry Pi 3b+. I decided to write all of this in Golang, a relatively new programming language designed at Google which features exceptional error-handling capability and a diverse ecosystem of already-written libraries and routines.
I decided furthermore that the motors and camera should be controllable by a simple
command-line tool called
mds-do (MDS is short-hand for Mobile Device
Sequencer). This CLI tool should, then, hook in to a library which I also would
write. The functionality is entirely implemented in this library; the CLI tool
is only an interface to call the functions exposed in the library.
For computer vision I settled on using OpenCV’s template matching to identify which areas of the mobile device’s screen needed to be touched by the stylus arm. The library then would identify the relative distance from this area to the stylus arm and move the device over the appropriate distance, lowering the stylus arm to activate the device’s capacitive touch screen and then raising it once the device had been touched. Because the stepper motors employed on either axis parallel to the phone were accurate to 1.8deg I had no trouble precisely touching the exact area of the screen.
The MDS parameters (motor speed, GPIO pinout, motor precision, etc. etc.) are
controlled by a
.toml file; this makes the MDS easily configurable and
.toml example configuration file looks like this:
# MDS configuration - .toml file # Install (after modifying) to: /pub/MDS-config.toml # Describes the physical configuration of a MDS # Wesley Coakley (firstname.lastname@example.org) [Sequences] Directory = "/path/to/sequences" # Finite state machine CSV files [Camera] File = "/path/to/image/file" # Input from camera (written to by `SnapScript`) CVFile = "/path/to/output/image" # Written to by MDS (output file, available for debugging) SnapScript = "/path/to/capture/script" # Script to snap a picture and put it at `File` Rotation = 0 # Rotate image 90, 180, or 270 deg. during pre-processing ServoResetPos_X = 1900 # Where is the servo arm X (from the camera's perspect.)? ServoResetPos_Y = 460 # Where is the servo arm Y (from the camera's perspect.)? PixelsPerInch = 190 # Experimental, depends on the camera resolution from `SnapScript` # Motor Wiring # ============ # The following three sections define the X, Y, and Z axis wiring schemas # # X-axis Motor # ------------------------------------- # Stepper motor (mounted on the bottom) # These pins plug into the DRV8834 breakout board # and drive a Sanyo Denki 1.8deg/step motor [XAxisMotor] Id = 0 EnablePin = 14 # (Blue) DirectionPin = 15 # (White) PwmPin = 18 # (Green) InchesPerRevolution = 0.4375 # Experimental value (run one `pulse`) StepsPerRevolution = 200 # 1.8 deg/step = 200 steps per rev. StepsPerSecond = 50 # Motor Speed in steps/sec # Y-axis Motor # ------------------------------------ # Stepper motor (mounted from the top) # These pins plug into the DRV8834 breakout board # and drive a Sanyo Denki 1.8deg/step motor [YAxisMotor] Id = 1 EnablePin = 17 # (Blue) DirectionPin = 27 # (White) PwmPin = 22 # (Green) InchesPerRevolution = 0.375 # Experimental value (run one `pulse`) StepsPerRevolution = 200 # 1.8 deg/step = 200 steps per rev. StepsPerSecond = 50 # Motor speed in steps/sec # Z-axis Motor # ------------------------------------- # Servo motor (stylus motor) # These pins plug into the L298 H-bridge [ZAxisMotor] Id = 2 ForwardPin = 9 # (Blue) BackwardPin = 11 # (White) # Debugging options # ------------------------------------- [Debug] GPIOEmulated = false # Don't try to toggle GPIO pins
The sequences in [Sequences/Directory] are CSV files which define the finite state machines powering each sequence for a given device; each line is a step, and the (successful) completion of each step warrants the attempt of the next step in the sequence.
Unfortunately I am not at liberty to share the Golang code nor any code from the project by contract; however I am permitted to share the details of its operation (as above) and to give insight into my design choices (also as above).
Design Day and Results
At the Senior Design Day this past Friday (2019, Dec. 6) I was unanimously nominated MVP of my team for my role as team-lead and programmer; although we didn’t win any prizes for our performance I am extremely proud of our execution and results, achieving nearly all of our core requirements and even some of our stretch goals. I feel that my capacity to manage a small group, especially in an environment where we are expected to rapidly prototype and spec a product, has greatly improved since having this experience.