- Published: Friday, 12 February 2010
- Written by Jon Chandler
- Hits: 12028
I've recently had a few applications where a wireless link would be handy. Looking on eBay, I found that Sure makes a 2.4 GHz UART module for a decent price (US$14 each on eBay including shipping). These are designed as a cable replacement, with a claimed range of 10 meters.The specs are here. Just a reminder - I have no relationship with Sure Electronics apart from being a satisfied customer. They offer some unique products at astonishingly low prices. Sure also has some modules in the 900 MHz range which offer greater transmission range but these operate on 3.3V.
The first test I made was to connect a module to each of the 2 PICkit 2s I have and test them out using the UART tool. Power, ground, transmit and receive and I was in business. Able to send messages both ways over a range of 2 inches! Not bad for the first attempt. The baud rate is fixed at 9600.
For something a little more challenging, I wrote a quick Swordfish program that sends "Ping" followed by a counter number every second. I used the TAP-28 board and easily connected the RF module to the UART connector. As luck would have it, the pins are even in the same order. I left the TAP-28 sending this message in my office and retreated to the far end of the house with the PICkit 2 and RF module connected to my laptop. This distance is almost twice the claimed range of 10 meters, separated by several walls and the floor (wood frame construction). If I held the antenna about 3 feet above the floor and rotated the module to the best position, I had solid reception of my ping messages. If I randomly laid the module on the chair, the results were a little more sporadic. I'd guess that within 10 meters, the performance will be reliable without any concern over positioning.
This picture shows the RF module connected to the TAP-28 board's UART connector. The module and board are being powered by the PICkit 2. This picture also shows the clearance between the daughter board connector and the 6 pins connectors which was questioned earlier. These's about 0.15" clearance beyond the centerline of the daughter board connector.
This is a closeup of the RF module. Note the familiar connector location on the right. The module is controlled by a PIC 24 series part. No documentation appears to be available for what's happening on the board.
The RF module has a choice of 8 frequencies in the 2.4 GHz band which are just below the frequencies used by my wireless network. No interference has been noted.
So what applications come to mind? A wireless data logger. Home control system. A remote control for my dSLR. Since long messages can be sent rather than just "button presses" the possibilities are endless!
The Sure documentation is here, since it can be difficult to locate.