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A project log for Cruise Control Preset

This project supplements the existing cruise control in a vehicle, allowing you to automatically set the cruise control to a selected speed.

Scott HammerschmidtScott Hammerschmidt 07/10/2015 at 18:500 Comments

Today I got some timings of how long it takes to refresh the display with both different buffer sizes and different things displayed.

Displaying the large '65' in the u8g_font_fub42n (as shown previously):

Page SizeTimer countstime (msec)
128 bytes35698142.8
256 bytes32137128.5

I then changed to displaying a small 11 pixel '65' using the u8g_font_fur11:

Page SizeTimer Countrstime (msec)
128 bytes26186104.7
256 bytes25931103.7

Finally, I mocked up the display to be like the one shown at the top of this project's page. I was concerned that perhaps the timer might wrap around, so I changed the division to 1/256 (thus the lower timer counts):

Page Size
Timer Countstime (msec)
128 bytes9990159
256 bytes8808140

The time varies quite a bit between displaying small graphics and large graphics. There wasn't as much change between the large 65 and the full mockup as I had expected. The page size has some effect, but not a lot (compared to the total time, or even the time differences between small graphics and large).

Here's what the full display mockup looked like. It was neat to actually see it on the screen on not just on the PC.

You can't see it in this photo, but the right 2 bars on the signal strength icon were hollow.

I might order the SPI version of this display and see how the timings fare with that interface. That will take a few weeks to arrive, so next I'll probably start on parsing the GPS data.

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