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Specification for Servo HAT?
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Specification for Servo HAT?

by wsmoak on Sat Dec 26, 2015 8:33 pm

Following up on viewtopic.php?f=8&t=85302&p=430060 on controlling the Servo HAT [0] with Elixir/Erlang...

There is low-level i2c support in elixir_ale [1] but I am having trouble reverse engineering the Adafruit Python code [2] to figure out what I need to do.

Is there a Specification or Datasheet for the Servo HAT that I can work from instead?

I went through the tutorial [3] but did not find anything at the level of what values need to be written to what registers for things to happen.

Thanks!

[0] https://www.adafruit.com/products/2327
[1] https://github.com/fhunleth/elixir_ale
[2] https://github.com/adafruit/Adafruit-Ra ... Example.py
[3] https://learn.adafruit.com/adafruit-16- ... i?view=all

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Re: Specification for Servo HAT?

by wsmoak on Sat Dec 26, 2015 9:53 pm

... okay, I think it's becoming clearer.

The Servo HAT for the RPi [0] says PCA9685, and searching for that leads me to the "Adafruit 16-Channel 12-bit PWM/Servo Driver - I2C interface - PCA9685" [1] which appears to be the bottom half of the Servo HAT .

So I think the RPi-specific HAT is based on this generic board/chip, and that item _does_ link to a datasheet: https://www.adafruit.com/datasheets/PCA9685.pdf

Can you confirm whether I'm on the right track? If so, please consider adding links between those two products to make this info easier to find. Thanks!

[0] https://www.adafruit.com/products/2327
[1] https://www.adafruit.com/product/815

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Re: Specification for Servo HAT?

by adafruit_support_mike on Sun Dec 27, 2015 3:41 am

The Servo Hat does use a PCA9685 to generate the signals that go to the servos.

I'll talk to the folks who manage the store pages about adding a link to the PCA9685 datasheet on the product page, and perhaps at the end of the tutorial. That's where we usually put them these days.

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Re: Specification for Servo HAT?

by adafruit2 on Sun Dec 27, 2015 2:00 pm

Added to tutorial! here it is too:
http://www.adafruit.com/datasheets/PCA9685.pdf

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