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: wifiMote Group No. 7
Team Member Completing This Homework: Prakhar Gupta
e-mail Address of Team Member: guptap@ 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 objective of the wifiMote is to design and create a wireless hand-held television (TV) remote. The remote will have a touch screen Liquid Crystal Display (LCD) interface that will be capable of receiving and displaying a TV video stream. The purpose of the wifiMote will be to allow a user to “channel surf” without interfering with what is being watched on TV. When the user manages to find a channel he/she would like to watch, they can then transmit it to the TV with the touch of a button. The device will have a 900 MHz receiver which will receive the video stream from a TV Tuner/RF transmitter.
The device will have an infrared (IR) interface which will be capable of interacting with the TV tuner in addition to the TV. The device will run on battery and will also have recharging capabilities. The user would be able to monitor the battery status (remaining battery) on the display. Some of the basic functionalities, such as increase/decrease of volume and channel, of the default TV remote will be supported.
2.0 Design Constraint Analysis
In this project, the major design constraint is to choose the right microcontroller. It should be able to support interfacing with the Infrared Transmitter, the touch screen controller, the LCD controller, the 900 MHz receiver and most importantly, should also have sufficient computing power to process and stream video on the LCD screen. At the same time, the microcontroller’s processing power and peripheral availability should not go under-utilized. Since the final product is going to be a handheld device, it is also necessary that it should have appropriate physical dimensions.
2.1 Computation Requirements
The most important computation requirement is to be able to process signals and stream videos. This requirement also has a real-time constraint associated with it, which is, that the time lag between the video stream on an actual television and the video stream on the LCD should be negligible because otherwise it would defeat the purpose of the device. Other than that, the microcontroller should also be able process the commands given by the user through the touch screen and put them to execution using the infrared emitter.
2.2 Interface Requirements
The microcontroller needs to interact with major functional components in order to make the device work. It interfaces with the LCD controller using SPI module and requires 43 I/O pins [3], with the touch screen controller using SCI module and requires 10 I/O pins [4], with the FM receiver using SPI and requires 1 I/O pin [5], with 2 infrared emitting LED’s using PWM module and requires 1 pin per LED and also with the battery monitor using ATD module and requires 1 I/O pin.
2.3 On-Chip Peripheral Requirements
On-chip peripherals will be needed to interface the microcontroller with the off-chip peripherals. These include 2 SPI modules, an SCI module, a 16 bit TIM module, and a PWM through the output compare channel.
2.4 Off-Chip Peripheral Requirements
Several off-chip peripherals will be needed to interface the microcontroller with the major functional components. These include an LCD controller, a touch screen controller, infrared emitting LED’s and an FM receiver.
2.5 Power Constraints
The remote is powered by rechargeable batteries, so all of the major components have to be as efficient as possible to maximize battery life. The microcontroller [1] and LCD controller both have an operating voltage of 3.3 [3]. The FM receiver module operates at 5 volts [5]. The touch panel controller can operate between 2.7 and 5 volts [4]. The LCD screen operates at 7 volts [2]. The largest drain on the batteries is going to be the LCD screen itself, and there isn’t much that can be done about that.
2.6 Packaging Constraints
The remote will be handheld, so the major constraints will be size, weight, durability, and operating temperature. The size of the LCD screen is 3.5” diagonally [2]; this means that the total size of the remote will be about 4.5”-5” diagonally. This is small enough to fit in one hand and use the other hand to make channel selections. The weight of the remote will not be critical, because one does not usually carry a remote in a pocket. The remote will have to be durable, because remotes have a tendency to get dropped, usually from about table height. Being able to survive a fall of a foot or two onto carpet would be ideal. The remote will be handheld, so it can’t get too hot to hold onto.
2.7 Cost Constraints
The estimated cost of the hand-held device will be around $230. Remote controlled TV tuners are available in the market for approximately $60. These tuners need to be interfaces with a 900 MHz transmitter which costs approximately $22. Therefore the total cost of the Tuner/Transmitter would be around $90 (including connection costs).
No products were found with the functionality offered by the wifiMote. The wireless remote by Acoustic Research (ARRU449) [14] serves a similar purpose although it cannot display live TV. This remote will be wifi enabled which would allow it to connect to the internet and display TV guides on its LCD screen. It is also capable of displaying information such as weather and news headlines. This device is will be available in October 2007 with an estimated retail price of $400. Our device serves the purpose of TV guides by actually displaying other TV channels. It also follows an estimated cost constraint of $400.
3.0 Component Selection Rationale
3.1 Microcontroller
The major criterion while selecting an appropriate microcontroller were cost, a clock speed of around 80-100 MHz [1], low power consumption and presence of important on-chip peripherals which included SCI, 2 SPI’s, TIM, ATD [1] and about 60 I/O pins. The two prime candidates for the microcontroller were Microchip PIC24HJ256GP210 32-bit microcontroller [1] and ATMEL AT91SAM7A3 32-bit ARM-based Microcontroller [13]. Although both the microcontrollers meet our requirements, we chose Microchip PIC24HJ256GP210 32-bit microcontroller due to a variety of reasons. Firstly, the economic factor – a single piece of Microchip PIC24HJ256GP210 can be purchased for $10.70 while ATMEL AT91SAM7A3 costs $15.70 a piece. Secondly, while ATMEL AT91SAM7A3 has a maximum clock frequency of 60 MHz [13], Microchip PIC24HJ256GP210 has a maximum clock frequency of 80 MHz clock. Lastly, ATMEL AT91SAM7A3 is based on an ARM-based architecture hence consumes more battery power than its competitor Microchip PIC24HJ256GP210.
3.2 900 MHz FM Receiver
The FM receiver module has to be low power to help conserve battery life. Distance will not be a factor, because even a 1mW transmitter/receiver system has a distance of about 500 feet, and the remote will be in the same room as the transmitter, so the distance won’t be more than 20 to 30 feet. Two candidate receiver modules are the R900V [5] by Applied Wireless and the 9XStream by MaxStream [8].
The R900V is specifically designed for video applications, which gives it a strong advantage over the 9XStream. It also has a bandwidth of 3Mbps, versus the 9XStream’s 19.2Kbps [8]. The 9XStream, however, has a better receiver sensitivity of -107dBm compared to -80dBm. This difference actually gives the 9XStream 32 times the range of the R900V [5]. But that advantage isn’t useful to this project, because the distances involved will be well within the ranges of both modules. The R900V is much simpler because it is specialized for video applications. The R900V also costs significantly less than the 9XStream; it is only $45 while the 9XStream is $150. The R900V ultimately wins because it meets the requirement and costs much less than its competition.
3.3 LCD
Two candidates for the LCD were the Sharp Microelectronics 3.5 " display and Microtips Technology 3.5" display [6]. Both displays are 3.5" and have pixel density of 240 x 320. The Sharp Microelectronics display is a QVGA transflective [12] display while the Microtips display is Color-TFT. Both the displays use analog inputs, so LCD controllers would be necessary to create these signals. The Sharp Microelectronics display does not have a touch panel while the Microtips display has a touch screen and touch screen is one of the requirements for our design. The major advantage of the Sharp Microelectronics display over the Microtips display is that the display Sharp Microelectronics has a TFT fluid type while the Microtips display has a TN fluid type which means that the Microtips display suffers from limited viewing angles. However, the cost of the Sharp Microelectronics display is $128 and the cost of the Microtips display is $77. So the Microtips display fulfills our need and is also a lot cheaper than the Sharp Microelectronics display. Therefore, it was more appropriate for inclusion in our design.
4.0 Summary
This document addresses all the planning and research done thus far in order to complete this project. It talks about the different design ideas and components that have been looked at by the team. It also mentions the choices made by the team with respect to picking a microcontroller, touch screen LCD, touch screen controller, and LCD controller and 900 MHz RF receiver. The rationale behind these decisions has also been discussed in the different sections.
The packaging plan and the different interfaces required for the project to be a success have also been discussed. This document gives a clear picture of our intended design plan and helps better understand the function of the wifiMote.
List of References
[1] Microchip Technology, “PIC24HJ256GP210”, microchip.com, [Online]. Available: http://ww1.microchip.com/downloads/en/DeviceDoc/70175F.pdf. [Accessed Sept. 14, 2007].
[2] Microtips Technology, “MTF-T035DHSLP-A”, microtipsusa.com, [Online]. Available: http://www.microtipsusa.com/product_pdfs/Color%20TFT/MTF-T035DHSLP-A%20(24BIT,%20parallel,%20external%20BL%20control,%20anti-glare,%20TP).pdf. [Accessed Sept. 14, 2007].
[3] Epson Electronics America, “S1D13A04”, datasheet.in, [Online]. Available: http://www.datasheet.in/download.php?id=534538. [Accessed Sept. 14, 2007].
[4] Texas Instruments, “ADS7843”, focus.ti.com, [Online]. Available: http://focus.ti.com/docs/prod/folders/print/ads7843.html. [Accessed Sept. 14, 2007].
[5] Applied Wireless, “R900V”, applied-wireless.com, [Online]. Available: http://www.applied-wireless.com/pdf/R900V.pdf. [Accessed Sept. 14, 2007].
[6] Applied Wireless, “T900V”, applied-wireless.com, [Online]. Available: http://www.applied-wireless.com/pdf/T900V.pdf. [Accessed Sept. 14, 2007].
[7] GRANDTEC, “TUN-2000”, dominioncitystore.com, [Online]. Available: http://www.dominioncitystore.com/servlet/the-69915/GRANDTEC-TUN-dsh-2000-Cable-dsh-Ready-Mini/Detail. [Accessed Sept. 14, 2007].
[8] MaxStream, “9XStream”, maxstream.net, [Online]. Available: http://www.maxstream.net/products/xstream/datasheet_XStream_OEM_RF-Modules.pdf. [Accessed Sept. 14, 2007].
[9] MaxStream, “Receiver Sensitivity”, maxstream.net, [Online]. Available: http://www.maxstream.net/spotlight/receiver-sensitivity.php. [Accessed Sept. 14, 2007].
[10] Applied Wireless, “Price List Module”, applied-wireless.com, [Online]. http://applied-wireless.com/pdf/PriceListModules.pdf. [Accessed Sept. 14, 2007].
[11] MaxStream, “XStreme Wireless OEM Module”, maxstream.net, [Online]. Available: http://www.maxstream.net/products/xstream/oem-rf-module.php. [Accessed Sept. 14, 2007].
[12] Sharp Microelectronics, “LQ035Q7DB03F”, document.sharpsma.com, [Online]. Available: http://document.sharpsma.com/files/LQ035Q7DB03F_SP_100505.PDF. [Accessed Sept. 14, 2007].
[13] At met Corp., “AT91SAM7A3”, atmel.com, [Online]. Available: http://atmel.com/dyn/products/product_card.asp?part_id=3578. [Accessed Sept. 14, 2007].
[14] Acoustic Research, “ARRU449”, gizmodo.com, [Online]. Available: http://gizmodo.com/gadgets/cedia07/acoustic-researchs-wifi-remote-stuffed-with-features-297312.php. [Accessed Sept. 14, 2007].
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ECE 477 Digital Systems Senior Design Project Fall 2007
Appendix A: Parts List Spreadsheet
* Devices that are not part of the handheld device
Vendor / Manufacturer / Part No. / Description / Unit Cost /Qty
/ Total CostDigi-Key / Microchip Technology / PIC24HJ256GP210 [1] / 32 bit microcontroller / $10.90 / 1 / $10.90
Mouser / Microtips Technology / MTF-T035DHSLP-A [2] / 3.5” LCD digital TFT Touch Screen / $77.44 / 1 / $77.44
Digi-Key / Epson Electronics America / S1D13A04 [3] / LCD Controller / $16.80 / 1 / $16.80
Mouser / Texas Instruments / ADS7843 [4] / Touch panel controller / $3.65 / 1 / $3.65
Applied Wireless / Applied Wireless / R900V [5] / 902 to 928 MHz FM Video Receiver / $45.00 / 1 / $45.00
amazon.com / Energizer / NH15BP-8 / 8 pack rechargeable NiMH AA batteries / $20.00 / 1 / $20.00
Applied Wireless / Applied Wireless / T900V* [6] / 900 MHZ FM Video Transmitter / $21.70 / 1 / $21.70
dominioncity / GRANDTEC / TUN-2000* [7] / Cable-Ready Mini TV Tuner / $66.43 / 1 / $66.43
TOTAL / $261.92
Appendix B: Updated Block Diagram
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