GTT70A Power

GTT TFT Support

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Haz
LCD?
Posts: 6
Joined: Wed Jun 28, 2017 8:52 am

GTT70A Power

Post by Haz » Sun Jul 09, 2017 8:06 am

Hi,

I have a GTT70A-TPC-BLM-B0-H1-CU-V5 and i am trying to figure out the power scheme.
I will be using the LCD in I2C mode in my end system, but for developing the screens, I am using USB.

1- I connected the USB to my PC through the USB storage, and I powered the display through the Alternate Power Connector with 5V, and it worked. I am able to connect and load screens, etc...
2- If i connect the I2C header, and supply 5V power and GND through connector called I2C Communication/Power Header I do not get power to the screen. The small green power LED does not light up. Is there a connection i am missing? a jumper i need to add? I only want 4 wires between the LCd and my main system, which are the 2xI2C connections, power and GND.

Please tell me what i am missing here to get the power setup connected properly.

Thanks,
H-

Daniel Divino
Matrix Orbital
Matrix Orbital
Posts: 92
Joined: Thu Sep 24, 2015 9:38 am

Re: GTT70A Power

Post by Daniel Divino » Mon Jul 10, 2017 9:45 am

Hi Haz,

It is interesting to hear that you are unable to power up your GTT through the I2C header. How much current is your power supply providing to the display?

The GTT70A uses a substantial amount of current in comparison to the smaller GTT displays that we offer. This is why we suggest that power is supplied through an alternate power header, as the I2C and 6 pin RS232 header are not capable of sourcing enough current for the display. That said, the I2C header should still be able to source enough current for an image to appear on screen, and for the LED to illuminate.

Please check how much current your supply is providing. You may need to increase the the current to ensure that the GTT can properly boot and operate.

Cheers,
Daniel Divino
Daniel Divino
Technical Support
Matrix Orbital

Haz
LCD?
Posts: 6
Joined: Wed Jun 28, 2017 8:52 am

Re: GTT70A Power

Post by Haz » Mon Jul 10, 2017 10:47 am

Daniel,

Thanks for the quick response. I have a 5V, 3A supply. I use the same supply to power the LCD from the power header or from the I2C header.
On the power header, I am using the 5V and GND pins only. That's the configuration which works. When i apply the same 5V and GND to the I2C header, it does not work.

If there maybe a jumper on the board i can check? I have all the tools to debug voltages on any test points you might need to help debug.

Thanks,
Haz

Daniel Divino
Matrix Orbital
Matrix Orbital
Posts: 92
Joined: Thu Sep 24, 2015 9:38 am

Re: GTT70A Power

Post by Daniel Divino » Mon Jul 10, 2017 11:41 am

Hi Haz,

Power through I2C should work out of the box. No changes to the board are necessary for the unit to be powered via I2C.

If you have a multimeter on hand, you can check for a voltage at pin 3 of D3; You should see 5V.

Cheers,
Daniel Divino
Daniel Divino
Technical Support
Matrix Orbital

Haz
LCD?
Posts: 6
Joined: Wed Jun 28, 2017 8:52 am

Re: GTT70A Power

Post by Haz » Mon Jul 10, 2017 10:48 pm

Daniel,
Let me walk you through the steps I have taken:

Powered the board through the I2C connector.
The green POWER LED is off.
Checked D3, which is right next to the I2C header.
The component is not populated. Just wanted to make sure that's intentional.
I am not sure about pin 3, but the pin with the dot on the silkscreen is at 5V. The other two pins are at 0V.
Below is the attempt at a diagram.
|0V
*|5V |0V

if I now power the LCD through the power connector, the LCD turns on
The green POWER LED is on
The voltages at D3 pins is
|4V
*|0V |0V

I have attached a picture of the back of the LCD, for your info.

Thanks,
Haz
20170710_214346[2022].jpg
20170710_214346[2022].jpg (264.47 KiB) Viewed 594 times

Daniel Divino
Matrix Orbital
Matrix Orbital
Posts: 92
Joined: Thu Sep 24, 2015 9:38 am

Re: GTT70A Power

Post by Daniel Divino » Tue Jul 11, 2017 12:07 pm

Hi Haz,

Since D3 is not populated, you will not be able to apply any power to the display through the I2C header. The I2C header is populated on many of our GTT's allowing for I2C communication but depending on the display, D3 may not be, preventing power through I2C. I am confirming with the PCB designers whether or not D3 should or should not be populated on the -CU display.

I see in your order, you purchase 2 GTT70A displays from us. Is D3 populated on your second display?

Cheers,
Daniel
Daniel Divino
Technical Support
Matrix Orbital

Haz
LCD?
Posts: 6
Joined: Wed Jun 28, 2017 8:52 am

Re: GTT70A Power

Post by Haz » Tue Jul 11, 2017 1:11 pm

No. Both of them do not have D3 populated.

I will wait until you hear back from your designers. I would be surprised if the LCD by design is not intended to be powered by the I2C header, when the description stated it is a USB and I2C. If it is, can you tell me what the part number is if i need to power it up through the I2C. I can only have a single connection from the LCD to the main board. I have had that for the prior LCD i have from MatrixOrbital, and changing HW is not an option.

Thanks for your help so far.

Haz

Daniel Divino
Matrix Orbital
Matrix Orbital
Posts: 92
Joined: Thu Sep 24, 2015 9:38 am

Re: GTT70A Power

Post by Daniel Divino » Tue Jul 11, 2017 4:26 pm

Hi Haz,

And to confirm, the I2C header is populated on both displays?

Cheers,
Daniel Divino
Daniel Divino
Technical Support
Matrix Orbital

Haz
LCD?
Posts: 6
Joined: Wed Jun 28, 2017 8:52 am

Re: GTT70A Power

Post by Haz » Wed Jul 12, 2017 7:42 am

No. I populated the header myself. Both came in without a header on the I2C.
But given that the LCD version i ordered specified I2C and USB communication, I populated it myself so i can use it. I even ordered the cable to connect to a breadboard.

So at this point, i have one LCD which has the header populated and one without.

Thanks,
Haz

Daniel Divino
Matrix Orbital
Matrix Orbital
Posts: 92
Joined: Thu Sep 24, 2015 9:38 am

Re: GTT70A Power

Post by Daniel Divino » Wed Jul 12, 2017 4:17 pm

Hi Haz,

I see. In order to supply power from the I2C header, you will need to populate the D3 pad with a BAT720 Schottky diode. You can find one of these diodes here.

Cheers,
Daniel Divino
Daniel Divino
Technical Support
Matrix Orbital

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