PmodMIC3 User Guide unavailable - link broken

[Happybacon]

We are trying to investigate whether the PmodMIC3 would be a suitable microphone to use for a project, but we cannot find details on how the 12-bits of digital data sent should be interepreted. There is a link on your website to a "user guide" but that link is broken. Go to https://reference.digilentinc.com/pmod/pmod/mic3/ref_manual and click "user guide", it will bring you to https://reference.digilentinc.com/pmod/pmod/mic3/user_guide where it says "This topic does not exist yet". 

Is it possible to repair this link so we can obtain this user guide?

Thank you very much.

[JColvin]

Hi @Happybacon,

Unfortunately, the user guide was not created; it was originally our goal to create user guides for each Pmod, but that was not feasible for all of our products. It also appears you are looking at an outdated version of the reference manual; the most recent version is available here: https://reference.digilentinc.com/reference/pmod/pmodmic3/reference-manual.

In the 'Timing Diagram' section of the reference manual, you will see that the 16-bits of data sent from the Pmod MIC3 start with 4 leading zeros, followed by the 12 bits of data MSB first. There are also some example projects for the Pmod MIC3 in its Resource Center here: https://reference.digilentinc.com/reference/pmod/pmodmic3/start.

Let us know if you have any questions.

Thanks,
JColvin

[Happybacon]

18 hours ago, JColvin said:

Hi @Happybacon,

Unfortunately, the user guide was not created; it was originally our goal to create user guides for each Pmod, but that was not feasible for all of our products. It also appears you are looking at an outdated version of the reference manual; the most recent version is available here: https://reference.digilentinc.com/reference/pmod/pmodmic3/reference-manual.

In the 'Timing Diagram' section of the reference manual, you will see that the 16-bits of data sent from the Pmod MIC3 start with 4 leading zeros, followed by the 12 bits of data MSB first. There are also some example projects for the Pmod MIC3 in its Resource Center here: https://reference.digilentinc.com/reference/pmod/pmodmic3/start.

Let us know if you have any questions.

Thanks,
JColvin

Hello @JColvin and thanks for your reply!

What we want to know is how the 12 bits of data should be interepreted. For example, are the 12 bits used together to represent one value? Or are some bits used to represent one value and the rest another? What physical property/properties of the audio input are represented by this value/these values? What we'd like to do is take the data from the PmodMIC3 and put it into a FFT in order to get the frequency of the sound.

Thanks

[JColvin]

Hi @Happybacon,

The 12 bits represent a single sample. Each sample that you take from the MIC3 represents (in a sense) both the amplitude and the frequency of the measured signal. The ADC takes the resulting voltage coming from the microphone (after it goes through some filters) and digitizes the signal. Because the incoming signal from the microphone will be sinusoidal since it is measuring sound waves and the ADC takes up to 1 MSPS, you can get a nice collection of data points where you can view how quickly the data oscillates between the top and bottom peaks (the frequency) and how high and low those peaks get (the amplitude). The circuitry for the Pmod MIC3 is set up so that it oscillates around the voltage midpoint (Vcc/2). You can then put the data through an FFT if you wish.

There is a demo of running audio data from a microphone through an FFT on a Nexys 4 DDR here: https://reference.digilentinc.com/learn/programmable-logic/tutorials/nexys-4-ddr-spectral-sources-demo/start.

Let me know if you have any questions.

Thanks,
JColvin