baantonia wrote:I've been trying and failing to get GPIO18-GPIO21 mode 3 functions (SPI slave) working for some time now using the original documentation with a range of Raspberry Pi, including the CM1. I see in this datasheet there are empty spaces. Was this function ever really available?
Better to start a new thread on SPI slave, although it's been done to death, and I see you already pinged one of the older threads viewtopic.php?p=810290
The CM3 is just using the same BCM2837 as Pi3, which is the same peripheral set as BCM2835 and BCM2836. Nothing has changed, and the ARM peripherals datasheet is the correct place to look for details of the interface, not the specific datasheet for one of the boards.
Whether they intentionally removed GPIO18-21 mode 3 descriptions or not I couldn't say, but there won't have been a change made to the silicon. Probably more that because no one has got it working (and looking at the firmware driver it is pretty much a stub) it wasn't seen as helpful to document it.