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Tensorflow lite: 3V jumper really needed for microphone
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Tensorflow lite: 3V jumper really needed for microphone

by pbackx on Sun Aug 30, 2020 11:54 am

I have the PyGamer and want to try and run the Tensorflow Lite example using the microphone.

I'm at the point where I want to connect the external microphone:
https://learn.adafruit.com/tensorflow-l ... t/assembly

Step 3 tells me to cut the 5V connection and solder the 3V pad. I think this is to change the voltage that goes to the D2 and D3 connectors, but I'm not entirely clear on that. Can some one confirm this?

In any case, on the microphone itself it is written that it works with voltages 2.4-5.5. So is changing the voltage even necessary? If yes, can some one explain why?

pbackx
 
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Re: Tensorflow lite: 3V jumper really needed for microphone

by mikeysklar on Mon Aug 31, 2020 11:18 am

Hello pbackx,

The PyGamer is a 3.3v based Microcontroller with a Cortex M4 processor. It will want all inputs to be at 3.3v to avoid damage. The Mic being plugged into D2 is going to be happy at either voltage (3.3v or 5v), but the microcontroller will not.

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Re: Tensorflow lite: 3V jumper really needed for microphone

by pbackx on Mon Aug 31, 2020 11:50 am

Thanks for the info! That explains a lot.

Does this mean I could also get away by adding a voltage divider to the out pin?

The reason I'm asking is that I may add other sensors in the future and I don't want to have to solder that connection every time I change something (although it appears, it's probably better just to switch to 3.3. I'm not sure why 5 is the default?)

Thanks again,
Peter

pbackx
 
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Re: Tensorflow lite: 3V jumper really needed for microphone

by mikeysklar on Mon Aug 31, 2020 7:38 pm

Most of our sensors support 3v so I'm a little surprised to see a 5v rail there. Maybe it is for NeoPixel strips and other such things that do better with a 5v line.

I would do the board cut solder change. If you really need to you can always setup a breadboard with a level shifters or use a less efficient resistor as you suggested for a voltage drop.

74AHCT125
https://www.adafruit.com/product/1787

mikeysklar
 
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Re: Tensorflow lite: 3V jumper really needed for microphone

by pbackx on Tue Sep 01, 2020 4:02 am

Thanks again.

I have some of those level shifters lying around, so in the meantime, I've switched to the 3V connection.

pbackx
 
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Joined: Fri May 11, 2018 5:58 am

Please be positive and constructive with your questions and comments.