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moving text display - Dear,code problem

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bohumilfulin

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codes for moving text

I am designing a moving text display. I have a problem with moving text to left or right.
The problem is the thickness of all characters is doubled. Exactly each vertical line has 2 pixels width but I can see 4 pixels. When speed is slow, everything looks ok but if speed is "average" or higher, all characters looks doubled.

I use high power LED but situation is the same for low or high contrast

HW the line of hc595+uln2803 (20pcs) for rows. rows are loaded by HW SPI
1pc hc595+uln2803+P_mosfet for columns loaded by FW spi. Multiplex 1:8.
MCU atmega128 @16MHz.

I know that most thinks are depend on HW but would you recommend me a flow diagram or piece of code for 100% working FW.

thanks in advance
 

moving text display

Hi,Post u r code & schematic.Then only we can find the bug.
 

moving text code

I am not entirely sure if SPI is fast enough for this, maybe worth checking out. Normal convention is row and column drivers. General principle is memory map leds, write to memory first, then enable leds. You obviously need to do this faster than persistence of vision.
 

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