January 1999, Issue 102

Wires, Wires Everywhere
The RF Solution

HERE COMES DE CODE

Final integration involves hooking the RF subsystem to a decoder. A number of dedicated chips are available from the likes of Motorola, National, Holtek, and Microchip. Or, you can roll your own using an MCU.

In principle, it’s relatively easy to design your own transmitter because the basic functionality involves gating the RF on and off. However, keep in mind that once you start talking, rather than listening, the FCC is going to insist on oversight. For all but the highest-volume apps, it may be wiser to purchase preapproved commercial units from outfits like Ming Microsystems, Abacom, Radiometrix, or DVP.

The easiest way to get started with the MICRF001 is to pick up the EV kit shown in Photo 1. It consists of an EV board (see Figure 5) combining the MICRF001 with a Holtek decoder, a keyfob transmitter from Ming Microsystems, and the requisite docs.

The kit offers just enough functionality to evaluate performance and perform range testing, a low-tech exercise that boils down to: press a button on the keyfob, see if the LED on the board lights up, move a step away, repeat.

All in all, the MICRF001 proves RF technology doesn’t have to be complicated or expensive ($3 in volume), thus enabling widespread adoption into new apps.

Although, technically, the MICRF001 could work in a wireless keyboard or mouse, FCC restrictions on the 300–400-MHz band rule it out. However, a Micrel app note does show how to use the MICRF001 as the second stage in a 900-MHz wireless modem.

I hope chips like the MICRF001 get the message to the PC powers that be: Wires? We don’t need no stinking wires.