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dektronics / printalyzer-timer

F-Stop enlarging timer and print exposure meter
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Improve return path layout around display module on the main board #47

Closed dkonigsberg closed 6 months ago

dkonigsberg commented 8 months ago

The layout around the display module connector on the main board could use some improvement. The ground plane should surround the connector more closely, perhaps even on the directly adjacent layers, and general routing of the SPI signals should be improved with careful attention to the return path.

Since the largest source of radiated emissions in preliminary testing appears to be the harmonics of the display's SPI frequency, and because probing has shown that its most strongly emanating from that connector, this is simply a place where its better to be paranoid than otherwise.

dkonigsberg commented 8 months ago

Just a quick update... Dropping the GPIO speed for the SPI pins from "Medium" to "Low" seems to resolve the emissions spikes, with no obvious downsides. However, some of this is still probably a good idea to look into for the next board revision.

dkonigsberg commented 6 months ago

Some minor changes implemented that should help, but there's a limit to what's practical here.