S17: Boom-Z Equalizer

Grading Criteria

• How well is Software & Hardware Design described?
• How well can this report be used to reproduce this project?
• Code Quality
• Overall Report Quality:
  • Software Block Diagrams
  • Hardware Block Diagrams

    Schematic Quality

  • Quality of technical challenges and solutions adopted.

Abstract

The purpose of this project is to allow the team to experiment with a sound reactive project. The team will use a specialized IC to convert the input audio signal into a digital signal that can be parsed by the SJSUone board. The team will also create the LED array grid that will be used to display the waveform/frequency representation of the audio signal. The final project should be able to take an input audio signal (using a regular audio cable/jack) and display some kind of frequency representation using the LED array grid.

Objectives & Introduction

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Introduction

The team split the project into two parts: The equalizer and the LED Matrix part. Thus, the team split into two sub-teams to tackle these two parts separately. The Equalizer task focuses on the conversion of audio input into an ADC output that can be parsed and create a data representation for the LED Matrix task. The LED Matrix task's main focus is to parse the converted data and drive the LEDs to display the appropriate representation of the signals.

Objectives

• design Equalizer hardware
• design Equalizer pcb
• design LED Matrix hardware
• design overall software architecture
• implement equalizer driver
• implement LED matrix driver
• integrate equalizer and LED matrix
• test overall system

Team Members & Responsibilities

• David Bui
  • Equalizer Hardware Design
  • Equalizer PCB Design

• Marvin Flores
  • Overall software design
  • Equalizer driver

• Adam Iglesias
  • LED Matrix driver

• Mina Yi
  • LED Matrix hardware design

Schedule

Week#	Date	Task	Actual
1	3/19	Delegate project tasks Prepare wiki Research implementation options Choose/order parts	Delegate project tasks - done Prepare wiki - done Research implementation options - done Choose/order parts - in progress
2	3/26	Complete software design phase Finish first draft diagrams Prepare freeRTOS tasks Read datasheets for the parts Begin PCB design	Complete software design phase - in progress Finish first draft diagrams - in progress Prepare RTOS tasks - in progress Begin PCB design - in progress
3	4/2	Implement software design Implement drivers Integrate LED matrix with its driver module Integrate graphic equalizer with SJSUone board and audio input Send PCB to be made	Implement software design - in progress Implement driver for MSGEQ7 - done Integrate LED matrix with its driver module - not yet started Integrate graphic equalizer with SJSUone board and audio input - done Send PCB to be made - in progress
4	4/9	Integrate LED matrix with the equalizer module via SJOne board	Reordered LEDS to be used. Found out LEDS used non-standard communication protocol. Soldered components to PCB. Implemented software design Equalizer part - done LED driver - in progress
5	4/16	Testing and Debug	Tested PCB (equalizer) Started interfacing new LEDs (SPI protocol) Started designing PCB for LEDs LED driver - in progress
6	4/23	Testing and Debug	PCB design LED - in progress LED driver - in progress task communication between Equalizer and LED driver - done
7	4/30	Testing and Debug	started LED prototype board (for backup)
8	5/7	Testing and Debug	LED PCB design finished and sent to shop
9	5/14	Testing and Debug	LED PCB received and started soldering
10	5/21	Ready for Demo Complete Project Report	Final Assembly/Integration of LEDs and Display Box

Parts List & Cost

Bill of Materials for Graphic Equalizer

#	Name	Purchase Location	Description	Quantity	Cost
1	MSGEQ7	[1]	7 Band Graphic Equalizer	2	$4.95
2	capacitor	HSC Electronics	.1 uF capacitor	7	$0.35
3	capacitor	HSC Electronics	33 pF capacitor	2	$0.40
4	capacitor	HSC Electronics	.33 uF capacitor	1	$0.35
5	capacitor	HSC Electronics	10 uF capacitor	1	$0.35
6	capacitor	HSC Electronics	100 nF capacitor	1	$0.35
7	resistor	HSC Electronics	200kΩ resistor	2	$0.05
8	resistor	HSC Electronics	22kΩ resistor	2	$0.05
9	power jack	HSC Electronics	power jack	1	$0.45
10	audio jack	HSC Electronics	audio jack	1	$0.45
11	voltage regulator	HSC Electronics	3V voltage regulator	1	$0.25
12	voltage regulator	HSC Electronics	5V voltage regulator	1	$0.25
13	male header pins	HSC Electronics	male header pins	1	$0.95

Bill of Materials for LED Matrix

#	Name	Purchase Location	Description	Quantity	Cost per item
1	LED Strip	Amazon	APA102C LEDs	1	$29.88
2	PCB	Bay Area Circuits	9.6" x 5"	1	$30
3	Shadowbox	Michaels	10" x 10", 4.5" depth	1	$32.99
4	Thin Plywood	Home Depot	9.5" x 9.5"	1	Varies
5	Power Supply	Amazon	Mean Well 5v 5A power supply	1	$13.22
6	3 Pronged Power Cord	Home Depot	Husky 8ft 3 pronged power replacement cord	1	$9.97

Design & Implementation

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Hardware Design

Graphic Equalizer

The main purpose of the graphic equalizer is to be able to take an audio input and generate an ADC output signal. The output values will be used to drive the LED Matrix values. The team decided to use MSGEQ7 chip for its simple design and ease of use. The MSGEQ7 Graphic equalizer can take an audio signal and 'split' it into 7 different frequencies. The team used two MSGEQ7 chips to separate left and right audio signal; this allowed the team to have more column of frequencies to display in the LED matrix.

The board design is very straight forward. The strobe and reset sources are driven at the same time to both MSGEQ7 chips; left and right audio input are split to each designated MSGEQ7 chip. The output for both chips are fed into the ADC inputs of the SJSUOne board. Voltage regulators are added to power the equalizer system and the SJSUOne board using one DC adapter. The tricky part was to write the software driver to parse the frequency outputs which will be discussed in the software implementation below.

Figure 1. Equalizer Schematic

LED Matrix

PUT LED MATRIX HARDWARE IMPLEMENTATION HERE

Figure 1. Equalizer Schematic

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Figure 1. Equalizer Schematic

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Figure 1. Equalizer Schematic

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Hardware Interface

In this section, you can describe how your hardware communicates, such as which BUSes used. You can discuss your driver implementation here, such that the Software Design section is isolated to talk about high level workings rather than inner working of your project.

The Equalizer board is driven using 4 GPIO pins. Two pins are used for left and right strobe pins, while the other two are used for resetting each MSGEQ7 chips. 2 ADC pins are used to read the chips' analog outputs. SJSUOne board's SPI interface was used to drive the LED matrix.

Figure 2. Hardware interface

Software Design

Show your software design. For example, if you are designing an MP3 Player, show the tasks that you are using, and what they are doing at a high level. Do not show the details of the code. For example, do not show exact code, but you may show psuedocode and fragments of code. Keep in mind that you are showing DESIGN of your software, not the inner workings of it.

The Equalizer task reads ADC values from the Equalizer Board and converts them into LED Matrix representation values. The converted values are then sent to the queue which the Matrix LED driver task is listening. The Matrix LED driver interprets the data and drive the LEDs to display the appropriate signal representation.

Figure 3. Software diagram

Implementation

This section includes implementation, but again, not the details, just the high level. For example, you can list the steps it takes to communicate over a sensor, or the steps needed to write a page of memory onto SPI Flash. You can include sub-sections for each of your component implementation.

Equalizer

The MSGEQ7 chip has a unique way of outputting the analog signals (as shown in the strobe timing diagram below). The software needs to drive the GPIO pins to generate the strobe signal. The strobe signal is needed to be precisely controlled in order to read the analog outputs properly. Fortunately, the chip doesn't have a very strict timing and only has minimum values for signal widths.

Figure 4. Strobe Timing diagram

The code below shows the ADC reading implementation. As shown, the task loops for 7 times to read 7 different frequencies (for left and right outputs.) A struct was used to represent the frequency values and to make it easier to send to a queue. Take note that the reading only occurs when the strobe pins are driven low. In order to read the next frequency, the strobe pins need to be driven high and then low again.

Code snippet

for(int i = 0; i<7; i++) {
    clear_pin(STROBE_PIN_LEFT); //Clear Strobe_Pin 2.0
    clear_pin(STROBE_PIN_RIGHT); //Clear Strobe_Pin 2.2
    current_time_us = sys_get_uptime_us() + 36;
    while(sys_get_uptime_us() < current_time_us);

    uint16_t leftRawValue =  readPinValueP026();
    uint16_t rightRawValue = readPinValueP131();
    frequencyData.left[i] = convertSignalToMatrixReadable(leftRawValue);
    frequencyData.right[i] = convertSignalToMatrixReadable(rightRawValue);

    set_pin(STROBE_PIN_LEFT); //Set Strobe_Pin 2.0
    set_pin(STROBE_PIN_RIGHT); //Set Strobe_Pin 2.2
    current_time_us = sys_get_uptime_us() + 36;
        
    while(sys_get_uptime_us() < current_time_us);
}

After this loop, the frequencyData is sent to a queue. The LED Matrix tasks listen to this queue and process the received data to drive the LED Matrix display.

LED Matrix

PUT LED MATRIX IMPLEMENTATION HERE

Testing & Technical Challenges

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Testing

Equalizer

The team used Salaeae Logic Analyzer and an online frequency generator to test the equalizer. Images below shows the captured frames from the logic analyzer.

Figure. 999 1kHz output from logic analyzer.

Figure.

LED Matrix

Put LED Matrix TESTING HERE

Technical Challenges

Equalizer Design

• Generating strobe and reading the ADC values need precise timing. One missed reading will messed up the data representation of the frequency values.
  • Using digital analyzer greatly helped the team debug the timing issues.
• The MSGEQ7 chip is very sensitive to noise. In reality, this chip wouldn't perfectly filter-out the surrounding frequencies; thus we should look only to whether or not the target frequency has the highest output voltage.
  • Using online frequency generators, together with the logic analyzer, helped the team debug the system.

LED Matrix Design

• Not all LEDs are created equal. The first set of LEDs that we bought used a non-standard communication protocol with very precise timing (in nanoseconds)
  • The team decided to move on and use a different kind of LEDs which use a standard SPI protocol
• Soldering LEDs is very time consuming and prone to mistakes.
  • Since we can't solder them earlier as expected, the team decided to create a back-up LED matrix board just in case the main LED matrix doesn't work.

Discuss the issue and resolution.

Conclusion

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Project Video

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Project Source Code

• https://gitlab.com/nivram07/lpc1758_freertos

References

Acknowledgement

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References Used

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Appendix

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