Main Site Documentation

Flicker issue with CP7 and micro sdcard module


#1

i have a flicker issue on my CP7 during access files from the sdcard.


GT.StorageDevice storagedev = sdCard.GetStorageDevice();

...

private void LoadFile()
{
    if (!CheckStorageDev())
        return;
    try
    {
        object[] dgdata = dataGrid.GetRowData(dataGrid.SelectedIndex);
        if (dgdata != null)
        {
            string filename = @ "\sd\" + dgdata[0].ToString();
            Debug.Print("Load " + filename + " to byte array");
            FileStream fileStream = new FileStream(filename, FileMode.Open);
            byte[] data = new byte[fileStream.Length];
            fileStream.Read(data, 0, data.Length);
            fileStream.Close();
            Debug.Print("done");
        }

    }
    catch (Exception ex)
    {
        Debug.Print(ex.Message);
    }
}


#2

On spider, right?


#3

yes, fez spider (fw 4.2.5)


#4

Hi,

Has this issue been resolved ? I also suffer some screen flicker although nothing anywhere near as bad as dera does in the video. I have recently upgraded to v4.2.7.0 which I have been holding off on because I use the StartupLogo, however I wanted to see if this solved the flicker and unfortunately it doesn’t. I am accessing a small XML file from the microSD card which is only about 5kb so I don’t see it for long, if it were useful I could increase my file size and see how bad I can force it to be.

Gus, is this a known issue ? If so, has it been fixed ? I saw in some release notes that there was an issue with this in the past, is this specific to SD/microSD and if so would it still exist if I switched over to USB ?

I am using a Spider with firmware v4.2.7.0, VS2010 and the latest libraries, if I can provide any further diagnostic information or test data please let me know.

Cheers, Swifty.


#5

Hi,

Is there any update to this issue ?

Cheers, Swifty.


#6

As I expected, the problem is in DMA not able to keep up with SD and display. The larger the display and the higher the frequency, the more load is put on the DMA.

One way is to lower the LCD clock in configuration. This may cause some flicker on the LCD. Another way is to dynamically lower the clock before accessing the SD card and then raising the clock again after done with SD. This still causes some flicker on clock is lowered but in most cases it is unnoticeable.

You can change the clock dynamically using Register class to access the LCD config registers directly in the processor.


#7

Hi Gus,

Many thanks for the update. Unfortunately this issue along with some other speed/UI update issues have forced me to look at alternative smaller displays, I have a G120 and Hydra on the way for testing but I hope a 4.3" screen is not going to put the same loading on the system.

Cheers, Swifty.


#8

You shouldn’t see this on g120 but let us know what you find.


#9

I’m getting screen flicker using Cobra 2 wifi with CP7 12V 2.5 A power supply using G120 Firmware Hotfix v4.2.9.10.
Its kind of annoying is there a fix for it?


#10

Can you define flicker? What we are talking about is chopping in the image and only happens when the system is max loaded. Is this what you see?


#11

It is cycling in brightness levels at approximately a 1 second interval
FYI I am using Tinkr2 for the graphics if you think that could be causing it I will contact Skewworks.


#12

What happens if you write a quick little app just to show a bitmap on the screen, does the flicker go away when running the new app? if its not flickering then we can rule out the hardware ;).

Also how long are your cables to the screen? Make sure its not interferance from other nearby modules or power sources by moving the screen away from these devices and ensuring the cables dont pass too close to other electronic devices.

I have the Cobra II and CP7 and only a 1.5amp supply but I see no flickering, I am not on the latest version though. Not yet anyway :slight_smile:

Paul


#13

I’m using long cables - 50cm. It’s not really near anything that would be causing interference.
I’ll try a simple bitmap and see how it goes


#14

tried shorter cables?


#15

Shorter cables solved the problem.
Is there something i can do to use the longer cables?
perhaps replacing with shielded cable?