Radio Transceiver - RFM12

Fig. 1 RFM12 Radio tranceiver

Description:

This board is a radio transceiver based around the RFM12 module from HopeRF. It is a cheap and relatively easy to use module, with good range for most low datarate radio/wireless applications.
It connects to a host with an SPI bus, up to 10 MHz.

The board can be powered from 2.5 to 5V.

Schematic:

The schematic is as simple as it can get. C1 filters the power supplies, and R2 pulls FSK high so the board can be managed completely through the SPI bus.
The CS signal is selected with JP1, the IRQ signal, when needed is selected with JP2. This signal goes down low when a event generating an interrupt in the module occurs.
The SPI interface is common across the SPI boards, and provides the following signals: SCK, MISO, MOSI, 3 chip select signals and power supply.

Fig. 2 Radio tranceiver schematic

Construction:

The PCB fits on a small single sided board. All components are on the top side.

Fig. 3 Radio tranceiver layout

Start with the 2 wire links between JP1 and JP2. Continue with the smd components R1, R2, C1 and LED1. You can leave JP1 and JP2 out, and solder the tracks to link the CS and IRQ lines. Then K1 and finally the RFM12 module.

The antenna can be either the onboard one, or a piece of wire. Make sure you solder the proper track beside PAD5. The lenght of the wire antenna depends of the base band of the module:

• 433MHz: 164.7mm
• 868MHz: 82.2mm
• 915MHz: 77.9mm

Pads 1 to 4 can be drilled to 3mm to fix the board, or put spacers.  

How to use / Testing:

To check the board, you'll need a pair of them, and run the SPI Radio transceiver tutorial. Just make sure you set the switch on JP1 to the proper CS line.

Files and links:

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  Pawel

  Posted at 2012-02-21 19:26:54

  Do you have any Eagle lib for RFM12 created? You have a schematic with this component but can't find the lib. If you have it please let me know through comment section on my website.
  Thanks

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