The tradeoffs of Raspberry Pi hardware documentation

[Rowan Patterson] informed us of a recent ticket he opened on the Raspberry Pi documentation repository GitHub. He asked about the lack of updates to the Raspberry Pi 4 USB-C power diagrams for this board. You may recall that the USB-C power issue was covered by us in July 2019, but the current official document Raspberry Pi 4 schematics still show the faulty implementation, with the DC pins shorted, almost two years later.

[Alasdair Allan], responsible for the Raspberry Pi documentation, mentioned that they were in the process of moving their documentation from Markdown at AsciiDoc, and said they would not have time for further changes until this is done. But then [James Hughes], a senior software engineer at Raspberry Pi, mentioned that the schematics might not update even after this change due to a lack of manpower.

As [James] pointed out, their hardware will likely never be opened, due to the NDAs signed with Broadcom. The compromise solution has always been to publish limited peripheral diagrams. Yet now even those limited schematics may not keep up with the revisions of the map.

A simple fix for the Raspberry Pi 4 schematics would be for a community member to reverse engineer the exact changes to the Raspberry Pi 4 board layout and mark them in a revised schematic. This should be a little more than adding a second 5.1kΩ resistor, so that CC1 and CC2 are each connected to ground through their own resistor, instead of being shorted together.

Still, you might want Raspberry Pi to update the schematics for you, especially since they have internally updated versions. But NDAs are forcing them to duplicate their efforts, and at least for now, that means their public schematics don’t reflect the reality of their material.

Sam D. Gomez