Testing Plan: - EE Senior Design



Testing Plan:

ANALOG SYNTHESIZER TESTING

Test each component of the analog synthesizer individually.

Envelope Generator:

We will breadboard the envelope generator based on the schematic. We will connect an oscilloscope to the envelope output. We will simulate the trigger and gate inputs using the microcontroller or breadboarded circuits. We will observe the output waveform and its variation based on the inputs from the attack, decay, sustain and release potentiometers.

Voltage Controlled Amplifier (VCA):

We will construct the VCA on another breadboard. We will connect the output to the potentiometer. The input will be waves from the function generator. The amp will be controlled by a potentiometer and a voltage source. We will vary the control voltage with the potentiometer and observe the output.

Once both of these circuits are functioning properly, we will connect the envelope output to the control voltage of the VCA. We will observe the output of VCA with an input from the function generator. We will make sure it corresponds with what we expected. We will also breadboard a speaker to the output and listen to the effects of modifying the envelope in realtime.

Oscillator Output:

We will program the microcontroller to output a square wave at one frequency. We will then breadboard a potentiometer and program the microcontroller to read its voltage. The microcontroller will take that voltage and adjust the frequency of the square wave appropriately. We will watch the output of the microcontroller using the oscilloscope and observe it as we change the potentiometer. The range of the output will be from 20 Hz to 20 kHz, the human hearing range. We will then expand the code to 3 different oscillator outputs that are controlled by three separate potentiometers. After this, we will breadboard another 3 to 1 audio mixer. We will observe the output of the mixer on the scope.

Voltage Controlled Filter (VCF):

The next circuit we will create is the voltage controlled filter. As with our other components, we will breadboard it. The control voltage will be adjustable via a potentiometer. We will use the function generator on the all input and watch the output using the oscilloscope. We will observe the VCF output as we adjust the input voltage on the potentiometer.

Next we will use the oscillator mixer output as the input to our VCF while keeping the potentiometer. We will watch the output on the scope and attach a speaker to hear the output.

Ring Modulator:

We will breadboard this circuit. Then we will use two function generators on each input and look at the output on the oscilloscope. Once we verify this is working properly, we’ll use the outputs of our VCF and VCA (with the envelope generator as the input to it) as the inputs and observe the output visually on the scope and audibly on the speaker.

MIDI input:

Next we will breadboard the MIDI input. We will hack the MIDI extension cable into a female plug and a male output cord that we will use to talk to our keyboard. We will make the MIDI circuit and program the microcontroller to read the input from the keyboard. We will then program the microcontroller to output square waves based on the MIDI input. These will be verified using the oscilloscope to watch the output of the microcontroller. This will again be confirmed on the oscilloscope. In addition, the microcontroller will output pulses based on the MIDI input. These are the trigger, which is a short pulse when a key is pressed, and the gate, which is high for as long as the key is held. These feed to the function generator.

Putting it all together:

We will connect all the analog systems together as shown in the block diagram and verify that all the systems are working together.

LCD TESTING

We will program the microcontroller to send various basic pictures to the LCD in matrices that we encode. Once we get these basic screens working, we will add the various functions that affect what is displayed on the LCD until we get it all working.

INPUT RECORD TESTING

We will wire our analog multiplexer into a breadboard with three inputs. We will send different control voltages to the mux and observe the output. We will observe the waveform on the oscilloscope and verify that it is working properly.

Then we will program the control microcontroller to read inputs from the record and stop buttons. Once these are working properly, we will send this input to the second microcontroller.

Record Microcontroller:

We will use the ADC built into this microcontroller to sample an analog audio input at 44.1 kHz. We will then send this data to an EEPROM buffer. Then it will go back to the microcontroller and to MATLAB using the EUSART and an RS to USB chip. We will program all of this in stages and make sure they are working until we get proper data sent to MATLAB. We will then convert this data, which will be a matrix, into a wav file. We will listen to this and verify that the record is functioning properly. The record will be activated and stopped by the control microcontroller.

We will attach the output of our input select the input of the record circuit and also attach the LCD to verify that they are all working in conjunction.

USER CONTROL TESTING

We will program the control microcontroller with all the functions watching for button input. We will program it to send the stop/record inputs as well as the input from the wheel over to the record microcontroller. This will then send the data to the computer using the EUSART and MATLAB. MATLAB will take the wheel information and convert it into MIDI data which will be read by the MIXXX software for scratching audio files. We will program all this and debug as appropriate.

The frequency inputs will output to the LCD and adjust the frequency of their oscillators. We will verify this on the scope. We will also test that the input select circuit is read by the microcontroller and updates the LCD appropriately.

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