ECE 477 Digital Systems Senior Design Project Fall 2007
Homework 3: Design Constraint Analysis and Component Selection Rationale
Due: Friday, September 14, at NOON
Team Code Name: _Team Health Monitor______Group No. __4___
Team Member Completing This Homework: _Joe Isca______
e-mail Address of Team Member: ______jisca@ purdue.edu
Evaluation:
SCORE
/DESCRIPTION
10 /Excellent – among the best papers submitted for this assignment. Very few corrections needed for version submitted in Final Report.
9 /Very good – all requirements aptly met. Minor additions/corrections needed for version submitted in Final Report.
8 /Good – all requirements considered and addressed. Several noteworthy additions/corrections needed for version submitted in Final Report.
7 /Average – all requirements basically met, but some revisions in content should be made for the version submitted in the Final Report.
6 /Marginal – all requirements met at a nominal level. Significant revisions in 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.
Comments:
Comments from the grader will be inserted here.
1.0 Introduction
The goal is to design and implement a weight and blood pressure tracking device which would allow users to view their progress remotely via the internet. There are very few constraints other than cost and the interface. The biggest constraint is that it be of a reasonable size and weight so that it could be moved through doorways and into different rooms by one individual. This should not be too difficult since the measurement devices themselves are easily manageable. The device should also be simple to operate and install. A single Ethernet cable and a power supply should be the only external interfacing required.
2.0 Design Constraint Analysis
The major design constraints of this project are the interfacing requirements to the external monitoring devices. The microcontroller needs to be able to support several different channels of communication of varying types. USP, SCI, SPI, Ethernet all need to be supported by the chip. The other constraints are much more flexible. Nothing is completely finalized yet, except for the communication requirements.
2.1 Computation Requirements
The device will not necessarily need to do any calculations just simply be able to store and retrieve data. There are two computations that will possibly be implemented. One would be to keep a clock so that the entries will be time stamped. This would only be necessary if the data was stored locally. If the entries were stored in a central server the software would be able to timestamp the data as it was transmitted back to the server. The other would simply compare the pin and user id to the stored entries during the time that the user is attempting to login. This is so minimal that nearly any microcontroller would have enough computational power to implement these two functions.
2.2 Interface Requirements
The interfacing requirements are fairly straightforward. All of the ‘modules’ we are purchasing have some form of a data port built into them. The challenge will be to find a way to manage all of the data streams. The magnetic card reader and the weight scale are based on rs232 serial format while the blood pressure monitor has a USB port on it. The screen is SPI based and the keypad will be a parallel interface. A microcontroller with the ability to support at least three UARTS and two USB would be ideal. The voltage requirements for the signals will need to 9 volts and 5 volts for the UART and USB respectively.
2.3 On-Chip Peripheral Requirements
The main need for the microcontroller is the amount of communication ports it has and the types that it can easily implement. The current I/O will likely be 2 channels of RS-232/SPI incoming and one outgoing, 4 bits of parallel general I/O input from the keypad, one USB communicating bi-directionally with the blood pressure monitor, and an Ethernet port.
2.4 Off-Chip Peripheral Requirements
Off chip constraints requirements would possibly be external memory, this would be necessary if an embedded web server was implemented, but currently the team has not been looking like it will very likely be attempted. If the web server is not implemented nearly all of the operations could be performed on the microcontroller.
2.5 Power Constraints
The power constraints are not that strict since the serial and USB have standard voltages of 9 and 5 volts respectively. There are no current intensive aspects of this project. The measurement devices have their own power regulators built into them so the bulk of the power consumption will be from an unregulated supply of 9 volts which is what both the blood pressure monitor and the weight scale operate at. A small regulated 9 volt supply with a 5 volt step down for the USB will be needed to power the microcontroller and send the data signals. This project is going to use a standard AC wall plug for power so the need for a more sophisticated power supply like a switch mode will be unnecessary.
2.6 Packaging Constraints
The packaging has not been completely decided upon yet. Two possibilities are have a single box containing all of the circuitry and interfacing which would be wall mounted at an easily used height. The other would be to construct a central column which at the top would be the control and display panel. Very similar to a mechanical medical scale where the person stands on the scale and sees the results at about chest height. The second would allow for easy portability of the unit by simply adding two wheels on the bottom. Either package would have its advantages and if this were being put into production, then both variants could be implemented. The device will have to be built fairly strong, but would not need to be as strong as a tank, just strong enough to handle a fair amount of wear and tear. The packaging should also keep in mind that if this were being used in a gym, that sweat and cleaner would likely be used on the surface so should be able to be cleaned without shorting out.
2.7 Cost Constraints
This project is not trying to compete with any known products. The main cost constraint is merely that of the college students trying to fund the project. If this were being put into production the cost of a single unit would likely be fairly expensive since high quality, high durability, highly accurate devices would need to be used. Currently the cheapest devices with the necessary ports and features are being used, but the quality of the devices is directly proportional to the funding and the budget.
3.0 Component Selection Rationale
The group had initially narrowed the search for the microcontroller to be used in the project to two candidates, The Atmel AT32UC3A1512, and the Freescale MC9S12NE64VTUE. These had very similar specs. They each have multiple SCI/SPI ports and Ethernet support. The Freescale operates at 5 volts [2] while the Atmel 3.3 [1]. The determining factor really came down to the fact that the Atmel had two integrated USB ports while the Freescale had none [1], [2]. The group, in the interest of trying to minimize the amount of extra interfaces, chose the Atmel AT32UC3A1512 and is in the process of acquiring several samples and development tools.
4.0 Summary
There are very few constraints for this weight and blood pressure tracker. Nearly every aspect is open for adjustment and improvement. The interfacing of the monitors will be the most exact and inflexible. Cost is there simply because of a minimal budget, while the rest will be just to minimize size and weight to make the device more easily manageable, but there is not an exact size or weight requirement that is needed.
List of References
[1] Atmel Corporation – Product Card, “AT32UC3A1512,” September 2007, http://www.atmel.com/dyn/products/Product_card.asp?part_id=4122&ListAllAttributes=1.
[2] S12NE Product Summary, “S12NE: Microcontroller,” September 2007, http://www.freescale.com/webapp/search.partparamdetail.framework?PART_NUMBER=MC9S12NE64VTUE&buyNow=true
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ECE 477 Digital Systems Senior Design Project Fall 2007
Appendix A: Parts List Spreadsheet
Vendor / Manufacturer / Part No. / Description / Unit Cost /Qty
/ Total CostAmazon / Omron / BP Monitor / 69.95 / 1 / $69.95
CrystalFontz / CrystalFontz / CFA634NFAKS / 4x16 Character LCD Screen / 45.00 / 1 / $45.00
Digi-Key / Atmel / AT32UC3A1512 / 32 bit Micro / 8.25 / 3 / $24.75
Global Industrial / Global Industrial / Weight Scale / 94.51 / 1 / $94.51
Kane Cal / Kane Cal / Magnetic Card Reader / 50.00 / 5 / $50.00
Additional Expenses/Buffer in Budget / 165.79 / 1 / $165.79
TOTAL / $450.00
Appendix B: Updated Block Diagram
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