JeeLabs Café

RF12DEMO

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The RF12demo sketch can be useful to test proper operation of RFM12(B) modules.

It lets you set up two nodes and send test packets between them via commands

entered on the serial USB connection. The basic settings are stored in EEPROM

so that you can configure a board and then use it at the remote end without

connecting it to a second computer.

HOW TO SET UP A SMALL WIRELESS TEST

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1.  First of all, get two units hooked up as described here:

        http://news.jeelabs.org/2009/02/10/rfm12b-library-for-arduino/

    I use "JeeNodes" for this, but that's just me:

        http://news.jeelabs.org/2009/03/05/jeenode-v2-pcb/

2.  Compile and upload this RF12demo sketch to both boards. The serial baud

    rate is set at 57600, you can change it in the source code if needed.

    You will need to install the "RF12" Arduino library module - eg. on Mac OS X

    I copied the "RF12/" directory to /Applications/arduino/hardware/libraries/.

3.  When run, the demo gets config settings from EEPROM to set up the RFM12(B).

    If this is the first time, it'll probably report "A i1 g212 @ 433 MHz".

4.  Change the node ID as follows: enter "<N>i" with <N> a number from 1 to 26.

    For a first test, you could just pick node ID's 1 and 2 for the two units.

5.  Change the frequency band as follows: enter "<N>b" with <N> one of: 4, 8, 9.

    These are the 433 MHz, 868 MHz, and 915 MHz frequency bands, respectively.

    You should pick the same band as your RFM12B modules, preferably.

6.  Set the network group (aka "house code") with the command "212g". Groups

    1..250 are available for the RFM12B, the RFM12 module *only* works with 212.

    Make sure you set all units to the same group or they won't see each other.

7.  You're all set for the first unit, disconnect and repeat for the other one.

8.  Ok, time to try sending a packet. First make sure both units are powered up.

    It helps to have both units connected to the same machine so you can set up

    terminal windows for both of them, but if you only have one unit connected

    to the terminal window and the other just powered up that's ok too.

9.  Enter "0s" on one unit. The other unit should report "OK" plus a number.

    If you can't see the output of the other unit, use "a" instead of "s". This

    will send a packet and also request and acknowledgement. If all is well

    you'll see a short "OK" response on the same unit as where you typed "a".

10. In the above test, you're sending packets with no actual data other than

    what the protocol itself requires to function properly. To include some test

    data use "1,2,3,0s" or "1,2,3,0a" with "1,2,3" being the actual data. This

    sends a test packet with 3 data bytes (you can send up to 66 data bytes).

    The "t" commands is available as shorthand for "0,1,2,...,63,64,65,0a".

11. To do some range tests, carry the second unit to a remote location and use

    "0a" or "t" to try and send some data across and get an acknowledgement.

    At some point you'll see packets drop out (which could either be the data

    or the ack return). Longer packets tend to drop out more quickly, because

    there is a larger chance of them getting disturbed by noise along the way.

12. You may see "?" replies instead of "OK". These are packets with an invalid

    checksum. These are either random noise or incorrectly received packets.

    If you leave the demo running long enough, you'll probably also get such "?"

    messages occasionally when the radio picks up some random noise.

13. Note that you *can* configure an RFM12(B) module to send/receive on another

    frequency band than the one it was designed for. You'll just get a lower

    range because the RF components will not be optimally tuned for these cases.

14. The code is fully open source - feel free to browse and make changes as you

    see fit. The latest version of this software is always available here:

        http://jeelabs.org/view/libraries/RF12/

That's it - have fun!