iphone Noise Filtration Hardware

Transcription

1 Iowa State University ECPE Senior Design iphone Noise Filtration Hardware Design Plan Michael Bullis Andrew Mungons Yang Yang 2011 Client Rockwell Collins Faculty Advisor Dr. Zhengdao Wang G r o u p M a y

2 Table of Contents Definitions... 2 Executive Summary... 3 Project Description... 4 High-level Concept Diagram... 4 Functional Requirements... 5 Input/Output... 5 Interfaces... 5 Physical Dimensions and Durability... 6 Component Specifications... 6 Microprocessor Requirements... 6 ADC/DAC requirements... 6 Design Considerations/Tradeoffs... 7 JTAG vs. USB vs. RS FPGA vs. Microcontroller... 7 Converter Interface... 7 Testing... 7 Expected Deliverables... 8 Cost

3 Definitions ADC ADC Resolution Algorithm CAD Codec DAC FPGA HDL I/O JTAG Microcontroller MIPS Noise Filter PCB TRRS Connector Analog to Digital Convertor A device that changes an electrical signal with continuously changing voltage into a signal with discrete voltage steps. The number of bits, or steps, used in an analog signal s digital conversion. A sequence of instructions, usually performed by a computer, used to solve a problem or perform a calculation. Computer-aided Design Engineering computer software that assists in the design process. Encode/Decode A device that encodes an analog signal to digital and then decodes it back to analog. Digital to Analog Convertor A device that changes an electrical signal with discrete voltage steps to a signal with continuously changing voltage. Field Programmable Gate Array An integrated circuit capable of being reconfigured to perform specific tasks. Hardware Description Language A computer language used to describe electrical circuits. Input/output Joint Test Action Group An interface used for testing, debugging, and programming computer chips. A computer chip that contains a processor, memory, and input/output ports. Millions of Instructions per Second A device that takes an audio signal, such as a phone conversation at an airport, and removes unwanted parts of the signal, such as jet engines. Printed Circuit Board Tip, Ring, Ring, Sleeve Connector A 3.5mm audio jack with 4 pins, commonly used on cell phones. 2

4 Executive Summary This is the design document for a device that will filter audio from a microphone to an iphone using a proprietary filter designed by Rockwell Collins. The device must be low-cost (~$50) and reprogrammable so that changes can be made to the algorithm over time. The following pages describe the functional, memory, and processing requirements of the algorithm. There is a brief discussion of possible design considerations, including using an FPGA vs. using a microcontroller. Next, there is an outline for testing the effectiveness of the finished device. Finally, there is a concise list of deliverables, along with a schedule of deadlines, and a rough estimate of individual team member s contribution. 3

5 Project Description Rockwell-Collins has designed a proprietary audio filter to remove extraneous background sounds from a cell phone s external microphone. In order to demonstrate the effectiveness of the filter, Rockwell Collins will need a small piece of battery-powered hardware to host the algorithm. This device will receive input from an external microphone via a TRRS audio connector. Only the microphone will be filtered; the left and right audio will be passed through. When the power is turned off, the microphone will also pass through, allowing normal, nonfiltered operation. In order to allow future changes to the algorithm, the hardware should be reprogrammable via an external interface. High-level Concept Diagram Programming Interface Mic Input ADC FPGA or Microcontroller DAC Filtered output Unfiltered Microphone (if filter is powered down) Unfiltered Left and Right Audio 4

6 Functional Requirements Input/Output The primary input to this device will be an analog microphone signal. On an iphone, this signal is transmitted on a 4-line cable with a 3.5mm TRRS audio plug. The device will have two female TRRS connectors, one for input and one for output. The pinout of the jacks are as follows: Tip Ring 1 Ring 2 Sleeve Left Audio Right Audio Ground Microphone Since left and right audio are not being filtered, these signals will be passed through the device unmodified. It should be noted that aside from the iphone, the above pinout is only used by a handful of phones. There are many other phones that use TRRS jacks with a different pinout, therefore care must be taken when using non-apple products with this device. The only other I/O aside from audio will be the programming interface for writing the algorithm to the device. The connector and interface communication method (RS-232, JTAG, USB, etc) will be chosen based on the choice of FPGA/microcontroller. Interfaces Interaction with the device will be relatively straightforward. It will include a single on/off switch. When off, the battery will be disconnected and the mic input will be directed around the filtering hardware straight to the output. This will allow normal, unfiltered use of the microphone when the device is powered off. Also, since the battery is disposable, a 5

7 compartment will be available on the outside of the device to allow easy access to change batteries. A computer interface will be needed to write algorithms into the flash memory for the filtering hardware. Such programming tools already exist, and are easily procurable online. If the tool chosen is not a part of a regular CAD program, ample documentation will be provided to assist in programming the device. Physical Dimensions and Durability This device will be used in a regular office environment. Therefore, heat, durability, and other extreme physical testing should not be necessary. However, the device should be able to withstand regular, everyday use. It should remain relatively small as to not be a nuisance to the end user. Component Specifications Below are the minimum operational requirements of the circuit components for processing the audio with Rockwell Collins filtering algorithm: Microprocessor Requirements 60 MIPS 100k Logical Elements bit DSP blocks 10 M512s RAMs 200 M4k RAMs 1M total RAM bits ADC/DAC requirements 16 bit resolution 8kHz sample rate Needs compatible serial/parallel interface to communicate with microcontroller 6

8 Design Considerations/Tradeoffs JTAG vs. USB vs. RS-232 There are many different serial interfaces for debugging and programming FPGAs and microcontrollers. JTAG is most often used, but USB and RS-232 are both common as well. Because of JTAG is common, this will be our first choice. However, the actual interface will depend on what the FPGA or microcontroller supports. FPGA vs. Microcontroller Rockwell Collins algorithm is presently available in both C and HDL, which means that either a microcontroller or FPGA could be used in this device. Both implementations are equally complex and require flash memory to store the algorithm. We have chosen the microcontroller implementation to keep the cost of materials minimal. Converter Interface The ADC and DAC converters will need to be connected to our microcontroller, so that audio can be passed into our filtering algorithm and output to the iphone. We will need to ensure that we have matching interfaces between the ADC/DACs and the microcontroller. Although I 2 C is the common interface to use for peripherals on the same circuit board, it may not be possible to find ADCs with this interface that meet the sampling rate and resolution requirements. Converters with the more complex SPI interface may need to be used instead. Testing The end product will be demonstrated with a test noise filtering algorithm. The algorithm will be implemented using Texas Instruments Stellaris C library. We will create unit tests to verify the correctness of our noise filtering algorithm prior to experimental testing against any waveforms. Before creating our PCB, we will test our hardware design using design software such as Quartus or ModelSim. We will attempt to use MATLAB in conjunction with one of these CAD tools to test and analyze our filtering algorithm. This will ensure that our design is functional and operational before we spend money on getting the board printed. 7

9 After a board is printed, we will test the device in variety of environments with varying levels of environmental noise. Our demonstration will showcase the device s ability to function in realistic noisy and noiseless environments. We will perform our tests with the filtering algorithm both enabled and disabled while capturing audio output for further analysis. Expected Deliverables The final product will include: Noise Filtering device built to specifications outlined in the design document; Full schematics for the PCB; and A basic low-pass filter program to demonstrate the device. This will be written in HDL (for FPGA) or C (for microcontroller). 8

10 Cost Listed below are the current costs of the components needed to create the device to host a noise filtering algorithm. Please note that either an FPGA or a Microcontroller is needed, not both. Item Cost TI Stellaris 3000 (Microcontroller) ~$5 Input jacks $1 16-bit DAC/ADC ~$15 each PCB Need fabrication quote once hardware is designed Project Box/Enclosure Dependent on PCB size ($5-$10 estimate) 9