ELECTRICAL DIAGRAM / PROBLEM - 1.2" 4-DIGIT 7-SEGMENT DISPLA

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mpx_23
 
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ELECTRICAL DIAGRAM / PROBLEM - 1.2" 4-DIGIT 7-SEGMENT DISPLA

Post by mpx_23 »

Hello all,

It is not to in my habbits to ask for help but I'm a little bit lost.
I encounter an issue with this component,and I don't understand what's happened. I suspect that I have a power supply problem.

But before exposing my problem in detail and the strange behaviour (It works a short time only when I don't connect V_io but freezes after some secondes) I need to understand how your backpack works?
Could you share me an electrical diagram of it (I can do it by myself, but I need to unsolder the display)?
Or could you confirm me that pin V_IO is only connected to the I2C pull-up resistances?
Also, which is the limite of the I2C pull-up resistances, I believe remember it was (is) 2.2kOhm?

FYI : I plan to connect on this I2C bus :
- 1x 1.2" 4digit http://www.adafruit.com/products/1269
- 1x 8x8 bicolor matrix https://www.adafruit.com/product/902
- 1x RGB LCD 4x20 characters https://www.adafruit.com/products/499
- 1x arduino due (or MEGA)
(of course, all of this provide by Adafruit ;) ), do you think, I need to change the PCB's resistances?

Thank for your time

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adafruit_support_rick
 
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Re: ELECTRICAL DIAGRAM / PROBLEM - 1.2" 4-DIGIT 7-SEGMENT DI

Post by adafruit_support_rick »

The eagle schematic files are here:
https://github.com/adafruit/Adafruit-LED-Backpacks

Can you post a picture of your display, showing your soldering and wiring?

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mpx_23
 
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Re: ELECTRICAL DIAGRAM / PROBLEM - 1.2" 4-DIGIT 7-SEGMENT DI

Post by mpx_23 »

Thank for your quick reply.

Finally I dropped down all of my table, and re-wired all components but with short lengths.
I also power directly my arduino on the 5V pin and LED devices.
And all works fine, except, of course that the displays was too close to the ECU... :p

Then, I increased lengths of wires SDA SCL and problems appear again : sometime the 8x8 display freeze and some time it was the 4 digit....
But now, it restart "automatically" when i press the reset knob. (before, i needed to switch off power) --> In my opinion I had also a power issue.

I need to investigate a bit on the I2C bus, and will also make diagrams and pics than you are able to help me.

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Re: ELECTRICAL DIAGRAM / PROBLEM - 1.2" 4-DIGIT 7-SEGMENT DI

Post by adafruit_support_rick »

How long are your I2C wires?

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mpx_23
 
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Re: ELECTRICAL DIAGRAM / PROBLEM - 1.2" 4-DIGIT 7-SEGMENT DI

Post by mpx_23 »

So please find the I2C toplogy.
ElectricalDiagramI2C-Problem.png
ElectricalDiagramI2C-Problem.png (46.32 KiB) Viewed 451 times
I understud nothing. Sometimes digits display freeze and sometimes the matrix, and sometimes both. Sometimes after 10 minutes, sometimes after more than 2 hour..

I also added this code, executed only when I pressed a swith.

Code: Select all

Wire.begin();
clockDisplay.begin(DISPLAY_ADDRESS);  // Setup the display.
matrix.begin(MATRIX_ADDRESS);  // pass in the address
Sometimes it's enough to "unfreeze" the display and sometime not, and in this cases I have to switch off power...

I used 10 years ago during my studies an I2C bus and remeber than I didn't have to take care of wiring, I used a 10m rubbon wire and works fine. (without shield nor twisted wires)
Do you know if it is possible to know the state of the bus, I mean the slave ACK when I send data?
Is there any problem with Arduino DUE and the I2C bus(due to the 3.3V IO level)

Thank a lot for your help, I'm totally lost... (and freezed too)
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Kitsune
 
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Re: ELECTRICAL DIAGRAM / PROBLEM - 1.2" 4-DIGIT 7-SEGMENT DI

Post by Kitsune »

adafruit_support_rick wrote:How long are your I2C wires?
Could you help me in my problem over here ?

Is this warranty thing ?

viewtopic.php?f=47&t=84602

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Re: ELECTRICAL DIAGRAM / PROBLEM - 1.2" 4-DIGIT 7-SEGMENT DI

Post by adafruit_support_rick »

100cm is not very long. Try adding some pullup resistors to the I2C lines. Connect 10K resistors between 5V and each I2C line.

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Re: ELECTRICAL DIAGRAM / PROBLEM - 1.2" 4-DIGIT 7-SEGMENT DI

Post by mpx_23 »

I tested with resistors close to the Arduino and after close to the end display.... still the same problem.

In fact it's no a display problem but I2C one.. I will investigate
--> first step, try to know the ACK of slave device (it's seem to be not simple)

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Re: ELECTRICAL DIAGRAM / PROBLEM - 1.2" 4-DIGIT 7-SEGMENT DI

Post by mpx_23 »

Hello all,

I found something interesting : all works fine until i grouped together wire to digit display (power and I2C on length 80cm).
Instantly when I group together wires, I2C displays freeze. Same thing if I powered by USB or and external supply.

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Re: ELECTRICAL DIAGRAM / PROBLEM - 1.2" 4-DIGIT 7-SEGMENT DI

Post by adafruit_support_rick »

Try twisting the power wires together. Also twist the SDA and SCL wires together. This will reduce interference between the two. sets of wires.

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mpx_23
 
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Re: ELECTRICAL DIAGRAM / PROBLEM - 1.2" 4-DIGIT 7-SEGMENT DI

Post by mpx_23 »

Thanks for your advice but it's worse now : it doesn't start. :p

I made a small topology diagram to show my purpose. Is there any problem with the potential pull-up? some at 3.3V and some others at 5V?
I read in the I2C spec that the High voltage level is 0.7xVdd. So it means that if I2C bus have to work with 3.3V and 5V devices, the pull-up should be linked to 3.3V?

http://www.nxp.com/documents/user_manual/UM10204.pdf

I'm open to any advice ;)
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Re: ELECTRICAL DIAGRAM / PROBLEM - 1.2" 4-DIGIT 7-SEGMENT DI

Post by adafruit_support_rick »

You need to run the I2C logic at the same level on both devices. On a Due, both should be run at 3.3V. Try running the 8x8 matrix at 3.3V. If it doesn't work well, you'll have to use a, I2C level shifter on the 8x8, like this one:
https://www.adafruit.com/products/757

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Re: ELECTRICAL DIAGRAM / PROBLEM - 1.2" 4-DIGIT 7-SEGMENT DI

Post by mpx_23 »

OK thanks, I will try and give my feedback after.
I'm waiting my package...

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