ECE 477 Digital Systems Senior Design Project Rev 8/11
Homework 3: Design Constraint Analysis and Component Selection Rationale
Team Code Name: FEST______Group No. 5_____
Team Member Completing This Homework: Gloria Budiman______
E-mail Address of Team Member:
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 project revolves around the testing of speakerphones. A speakerphone consists of a speaker and a microphone component. Hence a duplex testing procedure is necessary to test the speakerphone. Basic functionality of the hardware includes playing and recording audio files to test both components simultaneously. The device will interface with an SD card, which is where digital audio files will be read and recorded. Signal conversion needs to be done to properly interface the digital and analog components.
PSSC:
· An ability to measure delay between project’s components; the playback device, the telephone line simulator, the DUT which is the speakerphone, and the recording device.
· An ability to determine the frequency response of the DUT.
· An ability to “play back” audio files.
· An ability to record audio and write it to non-volatile (removable) memory.
· An ability to perform duplex testing of recording data and playing back data.
2.0 Design Constraint Analysis
The basic function of FEST project is to playback and record audio streams. Although 44,100 Hz is the standard sampling rate for CD-quality audio, the signals will pass through a simulated telephone line which will typically respond to a frequency between 300 Hz and 3,400 Hz [1]. Thus, by the Nyquist Rate, an 8,000 Hz sampling rate [2] with 16-bit data depth per channel is sufficient to facilitate signal transportation. The Microcontroller Unit (MCU) is constrained with only one storage media. Since the device is required to playback two different audio files and record two different ones simultaneously, an MCU which has a large, fast-access internal memory is desirable.
Modularity of the device is also highly desired. High failure-rate components, such as microphone, speaker, and telephone line simulator should be easily replaceable. Testing is a key component to ensure those components are in a good working condition. The telephone line simulator, speaker and microphone should support both independent and full-duplex testing modes.
2.1 Computation Requirements
The device will perform several well-known digital signals processing algorithm, such as Fast-Fourier Transform (FFT). Programming on an MCU which is hardware-accelerated for these purposes is highly desired. A normalized Least-Mean Square (LMS) algorithm will be performed to remove echo [3]. In order to measure time delay between in-device components, an auto-correlation algorithm will be used on four different points in the device [4]. These four points are located in the far-end, near-end, telephone line simulator, and DUT.
2.2 Interface Requirements
The device will be interfacing with an SD card in SPI mode, in which 4 pins are needed (CLK, Enable, MISO, and MOSI). LCD will be used to display general information for the end-user. SPI will also be used to interface with LCD, of which another 4 pins will be used. Two switches and two buttons are used to control the operation of the device. The two buttons are used to power on and off the unit, and to start and stop the tests. The two switches are used to select the type of testing procedure (refer to figure 2, 3, and 4 for different testing modes). Four pins are needed to communicate with the audio codec for proper signal conversion. Two of those will be digital audio input, and the other two will be digital audio output. An extra two pins will be used to adjust digital signal channel sequencing into and out of the codec.
2.3 On-Chip Peripheral Requirements
The device is required to playback two different audio streams as well as to record two different ones. To playback audio, data from the MCU will be sent serially to a pair of off-chip Digital-to-Analog Converter (DAC). To record audio, a pair of off-chip Analog-to-Digital Converter (ADC) will supply digital signals to MCU. SPI will be needed to interface with SD card and LCD.
2.4 Off-Chip Peripheral Requirements
The device requires an SD card as its main data storage. The audio files will be stored as Pulse-Code Modulation (PCM) waveform. With a sampling rate of 8,000 Hz and 16-bit data depth, a channel will consume exactly 16,000 bytes per second. With two read actions, a total of 32,000 bytes per second will be read from the SD card. Likewise, a total of 32,000 bytes per second will be written to the SD card.
As modularity is a constraint of the project, the codec must be moved outside the main MCU. Should failure or demand for higher quality codec arise; this component can be easily replaced without needing to replace the entire MCU. A codec that has capabilities to handle sampling rate of at least 8,000 Hz in 16-bit data depth is required. The codec needs to have at least two analog I/O and one digital I/O which can handle 2-channel sequencing. Two DAC and two ADC need to be present in the codec.
A condenser microphone will be used to capture audio signal coming out from the DUT. Similarly, a loudspeaker will amplify audio signal to be picked up by the DUT.
A MAX4063 [5] device is needed to convert a single-ended DAC input to a balanced output as required by the CH1840 [6]. An amplifier will be hooked in the circuitry to drive the loudspeaker. Low-pass filter and anti-aliasing filter will be used to achieve the desired recording quality from the microphone.
2.5 Power Constraints
The device is A.C. powered. Two level of DC voltage is needed to operate different components. The 5V-line is needed to power the MAX4063 and CH1840. The microcontroller and the codec will be powered from the 3.3V-line.
A battery will be necessary to keep the device operating in full 24-hours without interruption in consideration of a sudden power loss. There is no concern in regards to heat dissipation. Neither operating environment nor physical form-factor will cause the device to fail due to heat. No cooling is required as the device will be operated in room temperature.
2.6 Packaging Constraints
The device needs to be portable, but handheld form factor is not desired. Test system will typically be deployed in the field, so packaging that fits within a carry-on luggage satisfies the constraint.
2.7 Cost Constraints
The motivation of the project is the lack of availability of similar product in the market. The device will be the first to appear in the market.
3.0 Component Selection Rationale
Candidates for the MCU are TMS320F-28035 [7] and TMS320F-28335 which comes from the same processor family. Although the latter provides more spacious on-chip memory (256KB vs. 128KB) and higher performance (150 vs. 60 peak MMACS), the former was chosen due to lower pin count (80 pins vs. 176 pins) and it’s availability in a solder-able package. Other options that includes TI’s C5000 and C6000 family were also dropped due to the high pin count (176 pins and up to 700+ pins).
The rationale to use the codec comes from design modularity. Offloading signal conversion to off-chip peripherals grants modularity as well as extendibility. Signal conversion no longer burdens the main processing unit and additional channels can be installed simply by adding codec chips as opposed to switching to a different MCU. Codec that was considered were the PCM3008, PCM3070, TLV320AIC3204, and TLV320AIC23. PCM3008 is a low-end mono-codec offering which offers no programmable registers. The PCM3070 and TLV320AIC3204 come in QFN packages, which will hinder hand-soldering. The choice hence falls to the TLV320AIC23 [8] which is a stereo-codec that offers 24-pin TSSOP and programmable registers.
4.0 Summary
This report outlines the components that are interfaced with the device and the specific constraints. Analysis of constraints is focused on the two major components, the MCU and the audio codec. The report briefly summarizes how these two components interface with each other to facilitate signal transmission and conversion within the device. A brief overview of different test modes the device can perform is also provided. Additionally, the issue and impact of modularity is also discussed. The report also outlines the power, packaging, and component selection rationale which affects the total cost of the device.
List of References
1. P. Seibert. “What is the frequency of the North American Public Switched Telephone Network?” Internet: http://hubtechinsider.wordpress.com/2009/06/03/what-is-the-frequency-response-of-the-north-american-public-switched-telephone-network/, June 3, 2009 [Sep 12, 2011].
2. eFunda. “Sampling Theorem”. Internet: http://www.efunda.com/designstandards/sensors/methods/dsp_nyquist.cfm, unknown [Sep 15, 2011].
3. D. Duttweiler. (2000, Sep). “Proportionate Normalized Least-Mean-Squares Adaptation in Echo Cancelers”. IEEE Transactions on Speech and Audio Processing. [Online]. 8(5). Available: http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=00861368 [Sep 15, 2011].
4. K. Davis. “Introductory Mathematical Ideas: Correlations”. Internet: www.ma.utexas.edu/users/davis/reu/ch1/correlation/correlation.pdf, Feb 2, 2006 [Sep 15, 2011].
5. Maxim. “Differential Microphone Preamplifier with Internal Bias and Complete Shutdown”. Internet: http://datasheets.maxim-ic.com/en/ds/MAX4063.pdf, Jun 2011 [Sep 14, 2011].
6. Cermetek. “FCC Registered Data Access Arrangement (DAA) Module”. Internet: http://datasheets.maxim-ic.com/en/ds/MAX4063.pdf, Sep 2009 [Sep 8, 2011].
7. Texas Instruments. ‘Piccolo Microcontrollers”. Internet: http://www.ti.com/lit/ds/symlink/tms320f28035.pdf, Mar 2011 [Aug 28, 2011].
8. Texas Instruments. “Stereo Audio CODEC”. Internet: http://www.ti.com/lit/ds/symlink/tms320f28035.pdf, Feb 2004 [Sep 2, 2011].
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ECE 477 Digital Systems Senior Design Project Fall2008
Appendix A: Parts List Spreadsheet
Vendor / Part No. / Manufacturer / Model / Description / Unit Cost /Qty
/ Total CostMouser / 595-TMS320F 28035PNS / Texas Instruments / TMS320F28035 PNS / 32-bit Real Time Microcontroller / 9.13 / 1 / 9.13
Digi-key / 296-15031- 1-ND / Texas Instruments / TLV320AIC23 BIPWR / Stereo Audio Codec / 9.94 / 1 / 9.94
SparkFun / BOB-00204 / SD-MMC Breakout Board / 9.95 / 1 / 9.95
Mouser / 700-MAX 4063EUD+ / Maxim / MAX4063EUD+ / Differential Amplifier / 1.34 / 1 / 1.34
Amazon / B0000AQRSS / Shure / PG58-QTR / Microphone / 59.00 / 1 / 59.00
Amazon / B003YL3KUO / JLab / BFBFFP / Loudspeaker and Driver / 29.95 / 1 / 29.95
Jameco Electronics / Linear Technology / LT1086 / LDO 3.3V Voltage Regulator / 1.95 / 1 / 1.95
Mouser / 700-MAX7407 EPA / Maxim / MAX7407EPA / Anti-aliasing Filter / 5.45 / 1 / 5.45
TOTAL / 126.71
Appendix B: Updated Block Diagram
Figure 1: Preliminary Components Interfacing and Block Diagram Figure 2: Test Mode 0 (Far-End and Telephone Line Simulator under test) Figure 3: Test Mode 1 (Near-End with speaker and microphone under test) Figure 4: Test Mode 2 (Full-duplex test. Both end, telephone line, and speakerphone under test)
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