May 2004, Issue 166

Radio Roundup

easy-Radio MODULE

While ridin’ the range, I managed to rope a few easy-Radio data radios consisting of a 433-MHz pair, a 900-MHz pair, and a 900-MHz frequency-hopping pair. The 433- and 900-MHz modules are identical. The only way to tell the easy-Radio modules apart is to read their brand—ER400TRS for the 433-MHz modules and ER900TRS for the 900-MHz modules. Both frequency ranges of the easy-Radio module pairs can be plugged into a common set of evaluation boards, which are included in the easy-Radio evaluation kit.

I managed to take the “easy” out of the new easy-Radio evaluation boards by making assumptions and not paying attention to the documentation. The frequency-hopping easy-Radio modules, which are marked as ER900FHTRS, are larger than the non-hoppers because of some extra pins on the hopper radios. If you’re a Circuit Cellar regular familiar with your back issues, you know that I’m not new to easy-Radio technology (“RF Made Simple,” Circuit Cellar, issue 160, November 2003). 

In fact, some of the legacy easy-Radio equipment is still on the Florida room’s shelf. The legacy and new easy-Radio evaluation boards provide a socket position that accepts the slightly larger hopper radios. Of course, if it fits, plug it in. Right? 

Hours later, after trying all sorts of things, I could not get the new hoppers to talk to each other. I turned to the easy-Radio documentation out of desperation. I noticed that my new evaluation boards were void of the valid status LED. I unboxed my old down-level hopper evaluation boards and lo and behold there it was, the extra valid indicator LED. I started comparing the ER900FHTRS sockets on each evaluation board and found that the antenna pin for the legacy hopper modules on the new evaluation board had to be grounded, which is a subtle hint that you shouldn’t be using the new evaluation board to test down-level hopper easy-Radio modules.

I can get around that, I thought, so I flexed what I surmised to be the new hopper’s antenna pins to fit into the antenna pins on the smaller module socket behind the hopper socket. I could see the trace to the antenna from the smaller socket pin behind the hopper’s socket, and I thought this would make things all better. Ha! Nothing changed. Still no signal.

Further investigation of the ER900FHTRS version 2.00 Quick Start Guide pointed out that what I thought to be the antenna pin on the new modules is indeed a ground pin. Aha! So that’s what that pair of antenna coax leads are for. 

As it turned out, the new ER900FHTRS hoppers have an antenna receptacle cut out in the side frame of the easy-Radio hopper module that accommodates the coax antenna lead that came with the easy-Radio hopper evaluation kit. What was not obvious to me will be obvious to you if you take a look at Photo 4.

The smaller 433-MHz easy-Radio modules plugged right in and worked right out of the box. If I had slowed down and done some reading, I would have had the same success with the easy-Radio frequency hopper modules. In addition to the new antenna connection, the new easy-Radio ER900FHTRS radios can operate in Client/Server mode at 38,400 bps. An improved version of the easy-Radio configuration software on CD-ROM also comes with the new evaluation kits.