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Fonts in SPI memory


apiota
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There are some older posts, 2017 time frame about fonts in external SPI flash. The support team indicated it was not feasible and recommended loading into RAM and or filtering to make it smaller. Is this still the case or has anything changed regarding this ability since then?

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The problem here is a physical one that can't be overcome in software.

There are 2 fundamental issues:

  1. SPI flash is SLOW
  2. SPI flash is not memory addressable by the CPU

Yes, I know that some CPU's support memory addressing of SPI flash and in those the uGFX code works unchanged however the speed considerations are still a problem for practical use.

So, how to make SPI work for storage of fonts...

  1. Treat the SPI flash as a disk and connect it with the GFILE module
  2. Use the dynamic loading font mechanism to load the font you want into memory.

Whilst this still uses RAM for the font you have loaded, the advantage here is that it can be unloaded when not needed and potentially a different font can then be loaded from your SPI flash.

So, not a full solution but instead a work around. Unfortunately it is the only way to get around what is a physical hardware limitation. 

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