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Compute module 3 datasheet

Posted: Thu Oct 13, 2016 1:42 pm
by gsh
Thought people might like to have a look at James' hard work putting together the compute module data sheet, which includes CM3

https://github.com/raspberrypi/document ... /README.md

Re: Compute module 3 datasheet

Posted: Thu Oct 13, 2016 1:54 pm
by W. H. Heydt
Thank you very, very much for that. The CM3L is a surprise. The 4GB eMMC or the CM3 is a mild disappointment, but I'm glad to know for sure that that is what it will have.

Re: Compute module 3 datasheet

Posted: Thu Oct 13, 2016 1:57 pm
by 6by9
And now the reason for the new cmio is in the open - it needs to be able to support the cm3l :-)

Re: Compute module 3 datasheet

Posted: Thu Oct 13, 2016 3:14 pm
by 6by9
Neater to reference the doc via the raspberrypi.org domain - https://www.raspberrypi.org/documentati ... tasheet.md ;)

Re: Compute module 3 datasheet

Posted: Thu Oct 13, 2016 11:30 pm
by baantonia
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?

Re: Compute module 3 datasheet

Posted: Fri Oct 14, 2016 9:15 am
by 6by9
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.

Re: Compute module 3 datasheet

Posted: Fri Oct 14, 2016 9:28 pm
by Jim Manley
W. H. Heydt wrote:Thank you very, very much for that. The CM3L is a surprise. The 4GB eMMC for the CM3 is a mild disappointment, but I'm glad to know for sure that that is what it will have.
The purpose of the CM(3)(L) is embedded applications, so it won't need a full Raspbian distro for those. Something like a laptop/tablet would more likely need more flash storage, but that kind of device will have plenty of physical and USB interface room for off-CM(3)(L) storage.

Try DietPi to slice-and-dice down to just the features you need to get below the 4 GB limit and Robert's your parent's brother. Even better, just put the /boot partition in the 4GB eMMC, add another partition for whatever's left over, put your filesystem on a USB device, redirect to the filesystem via a config.txt edit, and you're good to go.