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TLC5957: The next line's color seems to slightly combined with the current line

qingnian LI
Prodigy 20 points
Part Number: TLC5957

I'm building a 16x16 LED matrix. According to the spec. description and the sample code,  send  First Line data, then input 65535 GCLK and the 2nd line data, repeat it 15 times. Then repeat the input of data and GCLK in a loop.

The color data of line 1 is blue to green gradients, the color data of line 2 is green to red gradients, same as line 3, line 4 etc.

But the actual color it shows is line 1-blue to green gradients with slightly red, line 2-seems to be just yellow. It seems to be the next line's color had combined with the currentline.According to the sample code, during the change of different line, the GPIO of different line has been compeletly shut down, and the digital multimeter shows they have been correctly shut down during the switch.

How could this happen, and how can i do to avoid this situation?

  • 0
    TI__Genius 12915 points

    Hi Qingnian,

    Could you help to share your schematic? From your description, it looks upside ghosting issue happened that some channels were slightly illuminated during line change. You could try just setting one color of one line to FFFFh and do not do gradient, see if other color or line are illuminated.

    To prevent it, you could try increase the line switch time for parasitic capacitor discharge, to see if it can help.

  • 0 in reply to Hardy Wu
    Prodigy 20 points

    Hi Hardy

    Great Thanks for your help. I've confirmed that the color do be illuminated.

    It helps to improve the display by increasing the line switch time, but to refresh the matrix quickly, i've to find another way.

    Finally, i found that just write the color of line to 0000h after the line switch, then the color will not be illuminated by other line.

    Thanks for your inspiration, it helps me a lot.