Connection via jumper wires does not start GD2 display

[bubu]

I am running into a problem with connecting my gameduino 2 with my arduino uno (r2).

When putting the GD2 on top of the gameduino, my sketch works exactly as it should, GD2 starts immediately displaying something.

When connecting the GD2 via jumper wires to the arduino (according to the pinout diagram), the gd2 does not power up fully (or so it seems) during the first time.

It flashes the Screen, but then stays dark. After about 10 resets, suddenly it springs to live and works as it should. When it works, then another reset is not a problem. But when I disconnect the power then the problem starts again and it needs several resets until GD2 Shows something.

I tried battery supply (9V battery) and USB cable, both behaving similar.

My guess here is, maybe the jumper wires are to Long or somehow interferring with both boards, because when I do not use them, there is no problem.

Because I need to use some pins on my Arduino in addition to the GD2, I need a something to lift the GD2 from my arduino.

Can someone give me a hint which jumper cables to use or what I should keep in mind to make sure, GD2 starts with every "power on" directly without needing to reset several times?

[jamesbowman]

This sounds most likely to be SPI signal integrity. The GD2 has two SPI devices on board, the FT800 and the microSD card. Both must start up properly for the system to work.

As an experiment, run "hello world" but modify the initialization like this:
GD.begin(0);This prevents the microSD initialization. Does this improve reliability?

By the way, how long are the jumpers? I have run the GD2+microSD on 6 inch (150 mm) jumpers:

[bubu]

My jumper wires are about 8 inches in length with the connectors on both side, cable only meassures about 7 Inch.

Using GD.begin(0) really improved the startup, as it now comes up and displays what it should every time.

I tried my own code with GD.begin(0) and this too comes up every time now.

Sadly, the touch screen is not working under this setup so i cannot press my buttons.

In addition I can see many vertical lines (moving) instead of a solid blue background in my sketch.

I then retried my sketch with GD.begin() again and as soon as I remove the SD card (while powered up), the sketch immediately starts running from beginning.

Putting the card back freezes the code sometimes and "reactivates" the reset problems.

I will try using shorter jumper wires from a different supplier next.

[jamesbowman]

OK, so it's clear that the microSD card is not working very well with a long jumper. microSD cards vary a lot, so it might be possible to find one that can drive an 8" jumper.

The touch and vertical lines may be power supply trouble. I would suggest trying a larger gauge wire for the +5V and GND connections. The backlight on the LCD draws a lot of current.

[bubu]

You were right with power supply trouble.
Exchanging the wires for +5V and GND already solved the problem even though I am still using the long ones on some other pins.
Thanks for your help.
I will stay with shorter wires from now on and only use the long ones on my breadboard.