635 Bitmap Characters *sometimes* Wierd

[wintermute3]

We use 635 USB devices in one of our products. Part of our initialization sequence programs the bitmap characters so we can display bar graphs. This works fine *almost* all the time, but sometimes some of the bitmap characters don't seem to be set properly. When they are wrong, they are consistently wrong (i.e. not random). Rebooting our device reinitializes the 635, and clears the problem. The protocol is error-checked, and we have never seen any other anomalies in any of the normal character display activity, so whatever this is is specific to the bit-mapped characters.

Any clue what may be going on here?

- Michael

Crystalfontz LCD Blog

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[starlon]

The code you're using to initialize the display might help someone figure it out.

 

[CF Tech]

Do you set the characters from your side every time you start, or did you set the characters long ago and save them as the boot state?

Either one should work. I am just curious which approach you took.

I have not heard of the custom characters in a serial or USB module getting corrupted. Ideally, if you can somehow pinpoint the situation where it happens, we would be able to track down why it happens and fix it.

As a debug tool, you could read the characters back using command 10. Comparing the result to what you originally set this would tell you if they are messed up, and that might help pinpoint the code that is triggering the corruption.

Please see if you notice any particular sequence that seems to cause them to get messed up.