Grounding again.

Here is a sketch that gives me grief on a Feather Huzzah but not on an Arduino UNO.

And I dont remember how the dotted line is with the Arduino.
Anyhow, should the dotted line be there or not ?

Thanks

Your schematic suggests that there are 2 connections to the PCA9685, ground and negative power supply. Is this really the case? Are they really not internally connected? I would think they are, rendering the question meaningless.

Yes, you need 0V on the PCA9685 connected to 0V on the Huzzah.

PerryBebbington:
Your schematic suggests that there are 2 connections to the PCA9685, ground and negative power supply. Is this really the case? Are they really not internally connected? I would think they are, rendering the question meaningless.

Yes, you need 0V on the PCA9685 connected to 0V on the Huzzah.

Thank you Perry.
And yes, it is really the case. The PCA9685 has 2 different (I think) circuits. One for the powering of the onboard logic circuit, the other for the distributed power to the servos if used. And they should not be connected, at least that is how I read it.
My question is:
Should the 0V from the PCA9685 be connected to the ground on the Huzzah (separate from the 0V on the Huzzah )?
My dotted line.

From the Adafruit site:

VCC - This is the logic power pin, connect this to the logic level you want to use for the PCA9685 output, should be 3 - 5V max! It’s also used for the 10K pullups on SCL/SDA so unless you have your own pullups, have it match the microcontroller’s logic level too!

V+ - This is an optional power pin that will supply distributed power to the servos. If you are not using for servos you can leave disconnected. It is not used at all by the chip. You can also inject power from the 2-pin terminal block at the top of the board. You should provide 5-6VDC if you are using servos. If you have to, you can go higher to 12VDC, but if you mess up and connect VCC to V+ you could damage your board!

hextejas:
Anyhow, should the dotted line be there or not ?

If you take a look at this diagram here ------ click here
------ the line down at the bottom of the diagram with the row of black coloured dots is 'extra'. And it is being used as as a external electrical connection for connecting the 'GND' pin of the PCA9685 to other other 'GND' pins of other devices.

Also, in your hand drawing diagram, you show a 'battery' ------ and your battery leads to a '+' and '-' pins on your hand drawing diagram. You must make it clear which part (pins) they are on the PCA9685 board. At the moment, it is unclear where the '+' and '-' are meant to be (on the PCA9685), because your diagram just shows '+' and '-' symbols.

Also, if ever unsure about whether two pins ---- such as two 'GND' pins are electrically connected together or not ...... you can remove electrical power from all devices, then use a multi-meter to see if the two points are connected (such as by resistance measurement, or by continuity beep test).

So assuming your 'dotted/dashed' line is removed (not connected up)....... and if your multimeter continuity test shows that the two GND pins aren't electrically connected ------- then it means that you will then need to use your dashed line.

The +, and - on the side of the PCA9685 are labeled V+, and GND as shown in this picture.
I think that they are separate from the VCC and GND.

I have some of those.

If you mean the GND on the middle connector at the top it's connected to all the other grounds. It must be, it wouldn't work otherwise (see my tutorial). V+ is the V+ along the middle of the output connectors.

Do you not have a multimeter?

I hadn't thought about using a multi meter to check the connectivity. DOH!!!

Hi,

hextejas:
I hadn't thought about using a multi meter to check the connectivity. DOH!!!

Can you measure short between the two gnds?
Tom... :slight_smile:

What may be confusing you on that Adafruit board, is that the power connection has a "super-diode" in series for reverse polarity protection.

Of course there is only one ground to the whole circuit.

Well, all the gnds are connected.