EVE 3 70G - USB2SPI Init problem

[eschmo]

Hello Matrix Orbital Team,

after i've failed to get 3 different EVE displays up and working since a year now.... i decided to get another one and the USP2SPI bridge just to check if i can find the Issue by myself.

But after connecting it to the board i simply got the same issues as with the other display i've had..

First try the shell just stopped after" USB->SPI bridge opened"
Finally these was caused by external ground connected to the pads because i wanted to supply extra current over my breadboard as it is requested within a couple of threads.

What is interesting is that when the USB2SPI board is hooked and powered up, there is no voltage shown on the Vin Pad. (Diode?)

When fully separated the circuids i get a chip ID delivered and the display turns on by accident. But the ID's delivered are wrong all the time and changing randomly on every try. I run the extra Voltage with 12V 2.5A powersupply at the USB2SPI

shell-1.PNG (12.33 KiB) Viewed 5935 times

shell-2_img_white.PNG (9.21 KiB) Viewed 5935 times

shell-3.PNG (11.45 KiB) Viewed 5935 times

shell-4.PNG (9.39 KiB) Viewed 5935 times

In the most cases, when trying to connect there is no output, but sometimes it initializes per accident and then i got output like that.

disp_ouput1.jpg (640.25 KiB) Viewed 5935 times

disp_ouput2.jpg (504 KiB) Viewed 5935 times

Running the DIsplay with my own code on a Arduino Due works quite the same but without initializing the display per accident.
There is just nothing more after getting "0x7C" delivered (so basically communication is okay).

Maybe anybody may have an Idea whats going wrong?!?

Thanks and best regards
Thomas

[Rudolph]

Hmmm, I misplaced my USB2SPI currently so I have to go with the manual.

You can not really use the EVE3-70G with the USB2SPI, at least not to display anything.
Even programming the flash with EVE Asset Builder is a gamble since the various versions of EAB do things like playing the logo animation or just switch on the backlight.

When you look in the EVE3 manual you see on page 15 under "9.4. Power Specifications" that the EVE3-70A uses 40mA for the Logic, upto 140mA for the TFT and typicial 465mA for the backlight.
This combined is easily in excess of 600mA.

Now looking at the USB2SPI, first off D1 is one of these tiny dual diodes in SOT23 case, these are not built to carry current.
There is no type in the schematic so I just searched thru Mouser and found PMEG2005CT which is a "500 mA low Vf dual MEGA Schottky barrier rectifier".
These 500mA are for an average current with AC though.
So yes, there is a good chance that D1 already is dead.

Next there is U3 which is an adjustable linear regulator in SOT223.
Now you can find these regulators with a maximum output current of 1A or even 1,5A.
But 600mA output will not work on this board.
5V - 0,4V (diode) - 3,3V = 1,3V
1,3V * 600mA = 0,8W
12V - 0,4V - 3,3V = 8,3V
8,3V * 600mA = 4,98W

So even with only 5V the regulator is heating the board for 0,8W and with 12V this goes up to 5W.
Even if this works, it won't work for long as the regulator is overheating.

Unfortunately there is no adapter with switching regulator, the Riverdi Hermes board has almost the same design.
Riverdi got one detail better though, they separated the backlight supply from the logic supply and the Hermes board allows
to power the backlight from a different source.
This is not an option for EVE2.
And for EVE3 you need to remove R1 and populate R4 with a 0R0 resistor, then you could use the Hermes board with external 5V for the backlight.
Can't tell what it is like for EVE4 since there are no specifications available so far.

To be clear, this was perfectly fine with 4.3" and below and doing ok for 5".
But all these adapters are not designed to actually use 7" and up.

[eschmo]

Hello Rudolph,

thank you for your input!

The Temp of U3 is a good point. Thanks so i will not go ahead with that external supply.
I go ahead with my breadboard (3.3V from a stepdown module powered by a Switching PS) over Vin pad but the same issues occur.

I've checked D1 in input direction with ~600Ohms on both inputs and block the other way so it should be okay so far.
Voltage output of U3 is stable as checked with Oscilloscope when display is not initialized (but powered).

osc_v_out.jpg (640.54 KiB) Viewed 5908 times

What i found during testing this afternoon was quite a bit strange.

When the Display is switched on by accident, the Voltage drops from 3.35 -> 2.7.
The average load at my switching PS is between 60-110mA.
Voltage Regulator @USB2PCI is around 40C°.

Basically the current should be balanced between both inputs. But either display isn't pulling so much current or it is not balanced between the 2 Inputs. is not easy to measure the current coming from USB2SPI with my technical setup at home.

[Rudolph]

The 3.3V lines are connected on the display, unless you removed R1 and populated R4 with 0R0.
This separates the 3.3V (pin 1) and BLVDD (pin 16) lines.
But then this still won't work with the USB2SPI kit since it has the two lines hardwired together.

Please provide a simple schematic of what you are actually doing, simple but complete with all the connections.
This helps you to think it thru and makes it easier to point out if there is anything wrong with it.
Right now I am not sure if what I believe you are doing is actually what you are doing.

Edit: and your scope can do screenshots :-)
Edit2: oh, das TDS ist auf Deutsch eingestellt