TI eZ430-Chronos and ISM Bands for RF Projects

An event like Hackaday Superconference 2017 is supported by many sponsors that want to reach that audience. An important part of the outreach is the bag of goodies handed out to conference attendees. One item was from Texas Instruments, offering a discount for the “eZ430-Chronos wireless development tool in a watch” which caught my interest.

Recent news in smart watches are dominated by Apple and Google. Very powerful but at a price point I find unacceptable. So while I’m intrigued by the idea of a wrist computer that I could write code for, I’m waiting for the market to mature and the price to drop.

Photo by Texas Instruments

It never occurred to me that there might be smart watch platforms that offer less power and capability, at a much lower price. If I had gone looking, maybe I would have found the TI Chronos watch earlier. A web search indicated it is about 7 years old so hardly cutting edge, but it is a wristwatch I could program, for around the same money as a non-programmable Casio watch from Target. The development kit also includes two USB devices: one is a programmer to deploy code to the watch, and the other lets software running on a PC to communicate with software on the watch via RF.

Following the instruction to search for “Chronos” on the store site, I got two results: eZ430-Chronos-868 and eZ430-Chronos-915. What distinguishes the -868 from the -915? I went looking for data sheets and other documentation to help me choose between them. But they all assumed the reader already knew which they’d want! It turns out this is an instance of a complete beginner tripped up by basic knowledge in the field. These numbers indicate the RF frequency the device operates on: 868 MHz vs. 915MHz.

These are frequencies of the ISM (Industrial, Scientific, Medical) radio bands, open frequency range that people can use with minimal regulatory requirements. People who have worked with ISM RF would have recognized 868 MHz as the ISM band common in Europe and 915 MHz for North America.

Well, we’re all beginners at some point. At least now I know.

Texas Instruments has a whole set of products for people who want to build RF solutions in the ISM radio band under the SimpliciTI brand. I like the fact that these hardware components are available, but I’m less thrilled with the fact the software development is based on tools by IAR Systems. I’m barely a beginner on Microchip’s MPLAB X, I really don’t want to learn another development stack right now.

I already have a set of things I want to gain proficiency on and have to choose where to spend my time. So as interesting as the TI smart watch development platform is, I’m going to have to set it aside as a distraction.

Sorry, TI!

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