A.Mac
Posts: 2
Joined: Thu Dec 14, 2017 4:28 pm

SD card license for 4-bit SD mode

Thu Dec 14, 2017 4:39 pm

I'm working on a project that will be using two CM3L modules, with 2 SD cards; one for the boot volume, and one for data logging. It's my understanding that in order to use 4-bit SD mode (as opposed to just using SPI) a HALA license is needed.

Does the Raspberry Pi Foundation have such a license so that the end user can use 4-bit SD mode to interface with an SD card, or are we required to purchase our own license?

PhilE
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 1879
Joined: Mon Sep 29, 2014 1:07 pm
Location: Cambridge

Re: SD card license for 4-bit SD mode

Fri Dec 15, 2017 9:44 am

I am not a lawyer, and you may want to ask one, but my understanding is that a licence is not necessary. This is some of the wording on the SD Association website:
In order to manufacture and sell Host/Ancillary Products, a prospective licensee may obtain the rights to the essential patents, trademarks, copyrights and design patents from one source by executing the SD Host/Ancillary Products License Agreement ("HALA") with SD-3C LLC.
The word "may" does not (to me) imply an obligation - I would expect to see "must" (or at least "should") were that the case. You would think that they would rather have people who don't need a licence thinking they do rather than vice versa, so I think this lets you off the hook.

I think (remember - IANAL) that provided you don't use the SD logos or trademarks no licence is required.

rzusman
Posts: 327
Joined: Fri Jan 01, 2016 10:27 pm

Re: SD card license for 4-bit SD mode

Fri Dec 15, 2017 12:53 pm

I'd like to know how you plan on booting the 2nd CM3L module.

Or, do you mean each CM3L module will have two SD cards?

A.Mac
Posts: 2
Joined: Thu Dec 14, 2017 4:28 pm

Re: SD card license for 4-bit SD mode

Fri Dec 15, 2017 4:36 pm

rzusman,

You're right I wasn't entirely clear in my original post. One of the modules will only have one SD card for the boot volume, and the other module will have two SD cards, one for the boot volume, one for data logging.

rzusman
Posts: 327
Joined: Fri Jan 01, 2016 10:27 pm

Re: SD card license for 4-bit SD mode

Fri Dec 15, 2017 5:42 pm

OK, then why not just use SPI? Is your data rate that fast?

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