recently I tried to combine a beaglebone, a LCD7 cape and the
Chipsee multimedia cape only to figure out that the combo does
not work (the multimedia cape was not designed for this according
to Chipsee service).
Before agai something, which will not work together...how can I
figure out, what capes will work together?
Thank you very much in advance for any help!
From a hardware perspective, understand what each cape does. Make sure they do not use the same pins by checking the documentation for what pins they do use. If they use the same pins, then they most likely will not work.
Another thing you can do is ask the manufacturer of the capes you want to purchase what other capes they will work with.
This isn’t straightforward, it needs a considerable amount of hardware knowledge to make that decision: - Recognize power pins and how they are used (the chance on conflicts here is small, but multiple power sources can lead to problems). - Recognize bus signals that can be shared. The I2C bus for the EEPROMs is shared by all capes, that doesn’t make the capes incompatible. - Recognize dedicated I/O signals that are impossible to share among capes. I’ve given it some thought to let the initialization from EEPROM do this, but it’s not straightforward and a lot of old (non EEPROM) configuration code makes it even harder. A manufacturer might be able to determine if two capes will conflict, but I don’t expect him/me to be able to name all capes that won’t conflict! Maybe add a compatibility matrix to the BeagleBone Capes page on circuitco.com ? It can be fed with community (and manufacturer) information about compatibility. – Bas
The page is already in the works, but will only work for those that register their capes there and will only be as good as the manufacturer’s are able/willing to test. Insuring some sort of “interoperability standard” is not something I intended for nor will support. There are too many permutations and the fact that having an LCD any where in the system wipes out a lot of functionality due to pin muxing, it isn’t something that is realistic.
We intended for the pin usage tables that are provided on each board, much like Arduino does, to be enough. But it seems we need something that requires less “attention” and just lays it out in a table. With 8 functions per pins, it is not possible to have every cape function with all other capes. It is best served by having a matrix that people can look at. As I said, it is in the works but will take a while to pull together.