Lab 5: Introduction to the Synthesizer

Transcription

1 Lab 5: Introduction to the Synthesizer ECE 2060 Spring, 2016 Haocheng Zhu Gregory Ochs Monday 12:40 15:40 Date of Experiment: 04/04/16 Date of Submission: 04/15/16

2 Abstract The purpose of lab 5 is to learn how to generate the signals for the timing and the signals for the various tones and team also would use for electronic music. The functional name used for the digital design that generates waveforms by cycling through pre programmed memory is a synthesizer. In the first part of the lab, team would build a relatively simple wave synthesizer using the megafuctions LPM_ROM and LPM_COUNTER. From the wave synthesizer, the team could observe a wave generators functionality. The second part is uses a bit shifting technique in an improved signal generator, known as a synthesizer. Introduction The purpose of this lab was to learn how to generate the signals for the timing and the signals for the various tones. The first part is to build a simple wave generator using a counter and Rom to generate the waves. The second part is to build a wave generator that implements bit shifting, creating a synthesizer. The synthesizer changes frequency easier than the wave generator. In lab 5, the team created two synthesizers. The first one should calculate the address and the second one could be used directly to create an output. Theory Calculation 1. P = f * 2^m For 32 bits: Theoretical: P =.025*2^32 = Experimental: P = Error = ( )/ = = % error For 8 bits: Theoretical: P =.025*2^8 = 6.4

3 Experimental: P = 6 Error = (6.4 6)/6.4 =.0625 = 6.25% error Calculation 2. P = (2^m / Fs) F => F = P/(2^m / Fs) => F = P*Fs/(2^m) Fs = For 32 bits: Theoretical: F = 46860* /(2^32) = Hz Experimental: F = 46860* /(2^32) = Hz For 8 bits: Theoretical: F = 46860* 6.4/(2^8) = Hz Experimental: F = 46860* 6/(2^8) = Hz Equipment and Procedures As with several of the previous labs, this lab had two parts Part 1: In the first part of the lab, the team took an existing Quertus project and.mif files and created the circuit as instructed. The goal was to create a wave generator. The team then used Signal Tap II to save a set of data points from the output, and used Matlab to create the graph in Figure 1. Part 2: During this part of the lab, the team was to make two different synthesizers. The team followed the instructions and created two different synthesizers, one using thirty two bit integers, which were bit shifted to when accessing the lookup table, and one using eight bit integers that did not require bit shifting. This required a different P value, whose value was derived in Calculation 1. Using Signal Tap II, the team recorded the wave pattern for the thirty two bit and eight bit

4 synthesizers. The data was then plotted in Matlab, and can be seen in Figure 2 and Figure 3 respectively.

5 Experiment Results Figure 1. Figure 2.

6 Figure 3.

7 Discussion and Suggestions Topic 1: Describe how the content of a ROM (.mif file) is converted to a continuous synthesized waveform. The Rom(.mif file) is used to synthesize the wave by each of the numbers associated with another number on a list. When a number goes into the Rom, the Rom would output the number associated with another one. All the numbers going through the Rom could make a wave. Topic 2: How do you multiply and divide by powers of 2 using bit shifting? Explain the process for both signed and unsigned numbers. To divided by powers of 2 in bit shifting for signed numbers, you should move the replace the end of the bus which is usually 0 by the power of the number you divided which is the changed the size of the bus. If you need to have the same size bus you just repeat the most significant bit by the number that is the power of two. To multiply by powers of 2 in bit shifting for signed numbers, you can add the 0 s equal to the number that is to the power of 2 to the end of the original sequence. To divide for unsigned numbers by powers of 2 in bit shifting, it is the same thing as signed but if you need to pad numbers just put 0 s instead of the pad numbers. To multiple for unsigned numbers by powers of 2 in bit shifting, you can add 0 s equal to the number that is to the power of 2 to the end of the original unsigned integer Topic 3: You are given a.mif file that has 512 words and each word is 32 bits long. How should you set up the sizes of the address bus and the q bus (data bus) of an LPM_ROM to use this mif file? 512 words and 32 bits long the size of the address bus would be 9 and the q would be 32. Topic 4: How do you change the frequency of the synthesizers made in project 2?

8 To change the frequency of the synthesizers in project 2 you would change the P value that is contained in the constant LPM. To calculate the P value, multiple the number of words by the normalized frequency. Topic 5: In future labs, we will be using the synthesizers to make musical tones. For each of the notes in the table below, calculate the P value both for m=8 and m=32. Round the P values to the nearest integer. Recall that normalized frequency f = F/Fs and Fs = sample/sec for this course. Music Note Frequen Normaliz P (m = 8) P cy (F) ed Freq (m=32) (f) B Hz C Hz D 294 Hz

9 Topic 6: Explain why the 32 bit address calculation is a better choice for music than an 8 bit address calculation In a 8 bit address address, you can only record 2^8 (256) different waves. In a 32 bit address, you can record 2^32 different waves. If you want to record a music which contains a lot of different waves, a 32 bit address could record much more waves than 8 bit address which means the more clearly you can perform this music. Also, the 32 bit address has a larger margin for error meaning that the signal will better stay at the intended frequency. In this lab the experimental frequency and theoretical frequency for the 32 bit synthesizer were nearly identical but the experimental frequency and theoretical frequency for the 8 bit synthesizer had a larger error. Conclusion In the part one of this lab, all of our group members master the skills to draw the ROM and counter s block diagram. Also, we understand that setting the ROM comes with the change of address bits. What s more, in the second part, we learned how to create a synthesizer and how to calculate its the P value. Acknowledgements All group members participated equally on the lab. Each member had a hand in writing and editing the report.