These changes are not complete, but in light of some recent developments I felt it was necessary to update the documentation of this project as soon as possible. It turns out that MAXIM is unable or unwilling to offer any license for the 1-Wire® slave protocol on a non-MAXIM IC. As a result of this revelation, a suitable alternative to the 1-Wire protocol must be found and used instead. For now, I have settled on Fox-Bus™, which has been developed by Chris Fox. This protocol is a free single-wire alternative to 1-Wire, and Chris is generously allowing this project to take advantage of his research to use his protocol. Chris has indicated that he intends to make more information available at <http://fox-bus.com/> in the near future. For historical purposes, below is the email exchange between MAXIM and myself. Note that MAXIM is simply asserting their right to not license their patent. While I may find patents like this one to be rather dubious, I respect the fact that this is their right---and you should too. Do not harass MAXIM about this subject, as doing so would be counter-productive. Besides, there are alternatives that are better than the 1-wire protocol for this application. Begin forwarded message: > From: Hal Kurkowski <Hal.Kurkowski@maxim-ic.com> > Date: August 10, 2011 12:34:12 PM PDT > To: Robert Quattlebaum <email@example.com> > Cc: Scott Jones <Scott.Jones@maxim-ic.com> > Subject: RE: 1-wire license agreement > > Robert, > > Thanks for your email. > > In response to your questions: > >> 1) Will you require that I license the 1-wire protocol from you for >> devices which I build for my own personal use? (limited to 25 devices, >> max) > > Any non-Maxim slave device that incorporates the 1-Wire protocol > would be considered to be in violation of Maxim's applicable 1-Wire IP. > >> 2) Would the incorporation of a DS2401 into the design implicitly >> license the 1-wire patent for the device in the eyes of your legal team? > > Incorporating a 1-Wire slave device within a system does not allow > unlimited use of the protocol by other, non-Maxim parts. > >> 3) Would Maxim be willing to license the 1-wire patent for devices which >> include no Maxim parts? > > We currently are not able to license you or your company for this > application. > > Hal Kurkowski > Managing Director > Maxim Integrated Products > > > -----Original Message----- > From: Robert Quattlebaum [mailto:firstname.lastname@example.org] > Sent: Thursday, July 21, 2011 3:46 PM > To: Hal Kurkowski > Subject: Fwd: 1-wire license agreement > > Hello Hal! I was referred to you by Chris Fox, in the email quoted > below. > > As a hobby project, I have been developing a capacitive soil moisture > sensor which utilizes a ATtiny25 microcontroller and a few passive > components. I intend to release this project as an "open-source > hardware" project, licensed under the CC-BY-SA-3.0 and GPL-2.0 > licenses. The project is generally documented in the following > links: > > http://www.deepdarc.com/2010/11/01/soil-moisture-sensor/ > http://www.deepdarc.com/2011/01/08/soil-moisture-sensor-update/ > http://www.deepdarc.com/2011/07/20/sensor-panel/ > https://github.com/darconeous/soil-moisture-sensor/ > > The use of the 1-wire protocol for communicating with the sensor > seemed like a natural fit, as it would allow the sensors to be > chained together easily. I was able to implement a 1-wire slave > interface in software on the ATtiny25, and it is working great. The > only issue is one of the 1-wire patent, which MAXIM owns. > > I figured that as long as the device contained at least one official > 1-wire component (such as the DS2401) that this may be sufficient > (via "patent exhaustion") to cover the entire device, so I adjusted > the design of the sensor to include a DS2401. However, I have > absolutely no resources to consider an option which might possibly > lead to litigation, so I wanted to clarify the issue with you > directly. > > At this time I am developing these devices for my own personal use, > but if there is enough interest I may make a production run of a > few thousand, perhaps sold via kickstarter.com. As such I wanted > to reach out to you directly to get a feel for what your views are > on this subject and to possibly discuss patent licensing options. > > Alternatively, I could abandon the 1-wire protocol entirely and use > a different non-patented protocol---but I think that using the > 1-wire protocol in this case adds significant value to the utility > of this product. > > So, my questions are as follows: > > 1) Will you require that I license the 1-wire protocol from you for > devices which I build for my own personal use? (limited to 25 > devices, max) > 2) Would the incorporation of a DS2401 into the design > implicitly license the 1-wire patent for the device in the eyes of > your legal team? > 3) Would Maxim be willing to license the 1-wire > patent for devices which include no Maxim parts? > > If there are any additional points which come to mind which are not > addressed by these questions which you think are relevant to this > project, please let me know. > > Again, at this point these devices are for my own personal use---I'm > just trying to get a feel for what my liabilities are with respect > to this project. > > Thanks for your time!
I can now enumerate the sensor as a 1-wire device and read out the soil moisture. Works with several 1-wire devices on the same bus. Still need to work out the exact protocol, but so far so good. Also adjusted the PCB design to take into account some lessons learned. Turns out just having one big sensor plane without a ground plane wasn't such a good idea after all.
This is me wrapping up several commits from last weekend.
git-svn-id: http://svn.deepdarc.com/code/soil-moisture-sensor/trunk@1010 d48f582a-3cf3-0310-b784-83b2ddae21dc