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Topic: How do I test a board ? (Read 767 times) previous topic - next topic

hextejas

I will try and take a meaningful picture and I am guessing that you would like to see my wiring so I will try and make it clear. BRB 

hextejas

#16
Nov 06, 2020, 06:06 pm Last Edit: Nov 06, 2020, 06:16 pm by hextejas
I will try and take a meaningful picture and I am guessing that you would like to see my wiring so I will try and make it clear. BRB
The wires are:
White = SDA
Yellow = SCL
Green = GND
Red = +3.3v

The red, blue and yellow at the top left are to a bench top power supply, +5.8v
The resistor 4.7k at the left goes from +5.8v to SDA
The scope shows what looks like a sine wave. Not at all what the UNO looks like. The probes are attached to PWM and GND

I am at a loss as to what to try next.

hextejas

Here's 1


hextejas


hextejas

I think that I will try a different example I save to remember titled Servo. The difference was that it drove a servo using a GPIO pin. I will try it with different pins including 4.

What do you think?

TomGeorge

#20
Nov 07, 2020, 06:35 am Last Edit: Nov 07, 2020, 06:39 am by TomGeorge
Hi
What is your scope looking at?
Where are the connections to?

What is your servo?
Link to specs/data?

Have you been able to operate the servo from the UNO, before using the expander?

PLEASE draw a circuit diagram, reverse engineer what you have a draw it out.
Include the  power supplies.

Thanks.. Tom... :)
Everything runs on smoke, let the smoke out, it stops running....

hextejas

Hi
What is your scope looking at?
Where are the connections to?
The scope connections are to the PCA9685,  PW5 and ground. I know what it is supposed to look like and this isn't right.

What is your servo?
Link to specs/data?
The servos and PCA9685 are working properly. The exact same connections and sketch but using an Arduino Uno, works just fine.

Have you been able to operate the servo from the UNO, before using the expander?
Yes

PLEASE draw a circuit diagram, reverse engineer what you have a draw it out.
Include the  power supplies.

Let me try and do that in a presentable fashion.

Thanks.. Tom... :)

hextejas

Well now the darn thing works. I can only imagine that one or more of the wires might be faulty. I think that I will try it a few more times before I make it permanent. 

TomGeorge

Hi,
I would say you have a faulty gnd jumper/connection.

Tom.. :)
Everything runs on smoke, let the smoke out, it stops running....

hextejas

Hi,
I would say you have a faulty gnd jumper/connection.

Tom.. :)
Mass confusion.
I powered the devices on this morning and the UNO worked fine whereas yesterday it did not.
The Huzzah still does not.
I replaced all the wires and the breadboard and the Huzzah is still no go.

Thank you for this hint Tom. Grounding issues are somewhat of a mystery to me so I will try to frame my diagram and connections clearly.
Before I try with the circuit diagram let me see if I can describe it in words.
I read the grounding thread here and I seem to remember that all the gnd and the ---(neg) connectors are tied together.
So following those rules, the following pins are connected.
Arduino Uno gnd
PCA9685 gnd
PCA9685 Servo power gnd
Desktop power supply-----(neg)
==================
Desktop power supply(pos)  +5.68v
=================================
PCA9685  V+ 5.68
PCA9685 VCC 3.23
PCA9685 SDA 3.23 <----on the Huzzah
PCA9685 SCL 3.23 <---on the Huzzah
==============================
Feather Huzzah
USB Connection 5V
===================================

I am about to give up on the Huzzah and look for an alternative.

Thanks

hextejas

And here is a rough sketch of what I have wired. pretty simple.


Southpark

#26
Nov 13, 2020, 07:52 am Last Edit: Nov 13, 2020, 07:54 am by Southpark
The jumper wires -------- we definitely can't trust them to be properly assembled. A batch of wires can actually have some of them open-circuit ------ and I find that the cylindrical-ended ones have more of a chance of being faulty (ie. open circuit, due to poor manufacturing/assembly from the factory).

It is often a good idea to use a multimeter to test the whole lot of them.

I'm sure that there have been many people out there in the world that had spent ages trying to figure out why their circuit isn't working (when everything looks just right) - only to find out eventually that there's a dud wire.

This isn't to say that there is a fault wire/connection for this particular case. But just got to watch it with those jumper wires.

And make sure that the alligator clip wires are ok too (with continuity test using mutimeter). The alligator clip wires are generally fine. But better make sure they're good too - just in case.


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