Thursday, June 20, 2013

Universal 8 Bit Graphics Library bug

A while back I posted a video that showed a strange bug that was happening with my oscilloscope LCD program. It used U8GLib or the Universal 8 Bit Graphics Library.  The video is available at,

** UPDATE ** This problem is caused by updating the data while it is being displayed.  The update must not happen within the display loop.

Then I made a perfectly working oscilloscope using the Universal TFT Library and a better LCD. So then I thought I would go back and see what was the problem with U8GLib.

To rule out the LCD display I purchased a KS0108 compatible display because I could run it with its own support software or with the U8GLib.  With the KS0108 driver, I could not scale the amplitude of the input waveform, a new issue.  However the sine wave turned out perfectly using the KS0108 driver.  Then the same software really went crazy when I tried to use the U8GLib drivers.  Here is the video on YouTube,

Does anyone else have this problem or know of a solution??

Here is a picture of what the display should look like;

 But this is what happens when you move the position control to center the sine wave;

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