I'm designing something which will use an SD card. The device will be able to read and write the cards, using publicly available specifications. Do I need to pay the SD card people?
I had the same concern just a few days ago. I am planning on using a microSD card internally inside a device for extra storage. I will only be accessing it via the SPI interface and not using any proprietary features. The end user will not even be aware there is a microSD card buried inside the device, so there is no need (or desire) to put a SD logo on the product.
I sent an inquiry to email@example.com. Their reply was "If your client's product will be interoperable with SD cards, they will need to sign the Host Ancillary Product License Agreement. SD Association membership is required in order to sign the HALA."
So it looks like we have to pay the piper to be completely legal. My understanding it is $3000 a year ($2000 for the membership, and $1000 for the HALA).
Please, please: don't build a SD host: build a MMC Host! that way, you can read SD cards, using MMC mode! off course, in order to use microSD, you will need the microSD -> SD (MMC) adapter. I believe that in this way, you don't need to pay the royalties, but if I'm wrong, somebody tell me!
Another issue to be aware of - having support for Microsoft's FAT filing system (on SD cards) in your device may infringe patents.
(I am not a lawyer) My understanding is that there's only a problem when using long filename support.
Howzzabout just signing on so you do not have to put a disclaimer on what would predictably be an SD card socket? Clearly your strict answer on interoperability (which you tested adequately, we imagine) is No; and if you look at MSDN you can cite their nice definition of free (if you really do not want to block out a single file occupied completely with XFS) on the matter of recently used filesystems. However, you surely want the fastest card access available and can access an organization with a common desire for this sensibility? Before we even start groaning years hence that it's not teracomm holodiamond-readable?