Download Very good – all requirements aptly met. Minor additions/corrections

ECE 477
Digital Systems Senior Design Project
Spring 2008
Homework 9: Software Design Considerations
Due: Friday, March 21, at NOON
Team Code Name: _RoboRubik_________________________________ Group No. __11__
Team Member Completing This Homework: _Tyler Heck___________
e-mail Address of Team Member: _theck @ purdue.edu____________
Evaluation:
SCORE
DESCRIPTION
Excellent – among the best papers submitted for this assignment. Very few
corrections needed for version submitted in Final Report.
Very good – all requirements aptly met. Minor additions/corrections needed for
9
version submitted in Final Report.
Good – all requirements considered and addressed. Several noteworthy
8
additions/corrections needed for version submitted in Final Report.
Average – all requirements basically met, but some revisions in content should
7
be made for the version submitted in the Final Report.
Marginal – all requirements met at a nominal level. Significant revisions in
6
content should be made for the version submitted in the Final Report.
Below the passing threshold – major revisions required to meet report
*
requirements at a nominal level. Revise and resubmit.
* Resubmissions are due within one week of the date of return, and will be awarded a score of
“6” provided all report requirements have been met at a nominal level.
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Comments:
Comments from the grader will be inserted here.
ECE 477
Digital Systems Senior Design Project
Spring 2008
1.0 Introduction
RoboRubik is a self-contained Rubik’s Cube solver consisting of a microprocessorcontrolled PCB with multi-colored LEDs under each cube face. A user interface is used to input
the current state of the cube via an embedded web server. The microcontroller contains a stored
algorithm to calculate the moves required to solve a Rubik's Cube from any valid starting
position. The cube has two different modes of operation. Help mode allows the user to follow
the steps leading to the solution with RoboRubik acting as a visual aid. Play mode gives the user
the ability to solve the RoboRubik cube manually using buttons located on each cube face.
The overall software design focuses on the ability of the microcontroller to receive the initial
cube configuration or “state” from the user interface, output this cube state to the LEDs,
determine the steps leading to a solved cube state, and change the cube configuration based on
pushbutton presses subject to the mode of operation. The details of the software considerations
and the software design flow are discussed in the remainder of this report.
2.0 Software Design Considerations
The software design of the RoboRubik project begins with the user interface. The graphical
user interface, GUI, used for the user to input the configuration of the unsolved cube is run on an
external computer. The initial configuration of the cube is transmitted wirelessly from the
external computer to RoboRubik via an internal Lantronix WiPort wireless network device [1].
The user interface has no use after sending the initial cube configuration to RoboRubik. Once
the cube configuration is received by the microcontroller from the user interface, the
configuration is output to the LEDs and the solving algorithm stored on the microcontroller
calculates the moves required to reach the solved cube state. The microcontroller then waits for
a pushbutton press to change the state of the cube depending on the mode of operation. In the
Help mode, the microcontroller will walk through the determined solution in a step-by-step
fashion upon a pushbutton press. In the Play mode, the cube configuration will be changed by
the microcontroller based on individual pushbutton presses. A single press represents a 90°
clock-wise “rotation” of the cube face corresponding to the pushbutton located on that face. It is
important to note the cube does not physically rotate. Instead the LED configuration changes to
visually represent a face rotation.
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ECE 477
Digital Systems Senior Design Project
Spring 2008
The overall organization of application code represents a hybrid of both program-driven and
interrupt-driven modes. While RoboRubik is waiting for the initial cube state from the user
interface, the application code utilizes a polled program-driven organization style.
The
microcontroller waits for the data from the user interface by constantly polling the wireless
network device. Once the data is received, the solution determined, and the cube configuration
output to the LEDs, the microcontroller enters the interrupt-driven mode. Until a signal to
change the cube state is sent to the microcontroller via a pushbutton, the present configuration is
sent to the LEDs. The pushbutton press fires an interrupt causing the cube state to change to
either the next step in the solution or by “rotating” a face of the cube in the Help or Play mode,
respectively.
It was decided to implement the command-driven or hybrid application code organization
since it was preferred to use both the program-driven and interrupt-driven code organization
styles. The polling program-driven application code organization was chosen while the cube is
waiting for the initial configuration from the user interface since the wireless network device is
the only device being polled requiring a small polling loop and small latency. The interruptdriven organization style was selected to be used during the process of changing the cube
configuration since the microcontroller will be constantly sending the configuration status to the
LEDs at the moment a pushbutton is pressed. This will require the microcontroller to interrupt
the current LED output configuration and change the state of the LEDs based on the mode of
operation.
There are three main data blocks stored in the microcontroller memory. The first of which is
a lookup table for the LEDs representing a transition diagram. Secondly, the solving algorithm
will be saved in memory. Also, the list steps produced by the solving algorithm will be saved.
The explicit memory locations of this data have yet to be determined mainly due to the lack of a
finalized solving algorithm. Since the microcontroller selected for RoboRubik has 128KB Flash
and 4KB RAM, it has been determined the amount of memory is sufficient for the application at
hand [2].
3.0 Software Design Narrative
There are four major blocks in the hierarchical arrangement of the RoboRubik code
modules; user interface, main program, configuration output, and pushbutton interrupt. The user
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ECE 477
Digital Systems Senior Design Project
Spring 2008
interface communicates with the cube via RoboRubik’s internal wireless network device as
mentioned above. The wireless network device connects to the microcontroller serially through
the microcontroller’s SPI interface module [2]. The main program stored on the microcontroller
sits in a polling state until receiving the initial configuration data from the user interface at which
point it switches to an interrupt-driven mode of operation. In this interrupt-driven mode, the
configuration output displays the cube state via LEDs using the PWM module of the
microcontroller [2]. While the cube state is displayed, the main program is interrupted at the
press of a pushbutton causing the state of the cube to be changed according to the mode of
operation and the specific pushbutton pressed.
The graphical user interface allowing the user to input the initial cube state has been
completed. The wireless network device has been tested and shown to successful send and
receive data in a stand-alone fashion.
The device has yet to be combined with the
microcontroller to receive information from an external computer wirelessly.
The
microcontroller has been programmed to continuously strobe LEDs. The RGB LEDs used by
the design have yet to be integrated into the microcontroller strobing program to allow for
multiple color displays [3]. A simple program using a pushbutton to change the configuration of
LEDs has also been successfully tested using single-color LEDs. The algorithm used to “rotate”
the cube has not been fully realized. Additional features requiring further software design have
been suggested for implementation, but have not been tested or outlined. Some of these features
include multiple buttons presses corresponding to on/off switch, change of mode, and return to
initial cube state. Also, the idea of displaying the solution status, the number of steps left to
solve the cube, on the user interface has been discussed.
These extra aspects are in the
preliminary design stages and will be integrated once the core software design is completed and
successfully tested.
4.0 Summary
The software design of RoboRubik consists of the above mentioned considerations and
narrative. The two main organization aspects of the software design correspond to the receiving
of the initial cube state and the altering of the current state. While receiving the initial state, the
main program runs in a program-driven fashion. The main program operates as an interruptdriven organization mode during the changing of the current state.
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ECE 477
Digital Systems Senior Design Project
Spring 2008
List of References
[1] Lantronix WiPort Wireless Network Device Data Sheet, [Online document], 2006 Mar,
(Rev. 1.0), [cited 2008 Mar 20], Available HTTP:
http://cobweb.ecn.purdue.edu/~477grp11/files/datasheets/WiPort_Data_Sheet.pdf
[2] Freescale MC9S12C128 Data Sheet, [Online document], 2004 Oct 27, (Rev. 01.10), [cited
2008 Mar 20], Available HTTP:
http://cobweb.ecn.purdue.edu/~477grp11/files/datasheets/Microcontroller%20MC9S12C12
8%20-%20Freescale.pdf
[3]
TT Electronics OVSRRGBCC3 LED Data Sheet, [Online document], 2007 Nov, [cited
2008 Mar 20], Available HTTP:
http://cobweb.ecn.purdue.edu/~477grp11/files/datasheets/LED%20%20TT%20Electronics%20OVSRRGBCC3.pdf
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ECE 477
Digital Systems Senior Design Project
Appendix A: Flowchart/Pseudo-code for Main Program
Initialization
Receive Initial
Configuration
Display Cube
Configuration
Calculate Solution
Mode of Operation
Help Mode
Play Mode
Cube “Solved”
Figure A.1: Flowchart for Main Program
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Spring 2008
ECE 477
Digital Systems Senior Design Project
Help Mode
Pushbutton
Press
Step Through Solution
No
Display Cube
Configuration
Cube Solved?
Yes
Cube “Solved”
Figure A.2: Flowchart for Help Mode
Play Mode
Pushbutton
Press
“Rotate” Face
Display Cube
Configuration
Figure A.3: Flowchart for Play Mode
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Spring 2008
ECE 477
Digital Systems Senior Design Project
Appendix B: Hierarchical Block Diagram of Code Organization
User Interface
Main Program
Configuration
Output
Pushbutton
Interrupt
Figure B.1: Block Diagram of Code Organization
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Spring 2008