View Full Version : 912MHz transceiver help

03-30-2009, 11:53 AM
I need some help with RF communication involving two 912MHz transceivers.

(These are the transceivers that Andy used at the CSU, Sacramento Engineering fair just a few moths ago). See attachment for more details.

I have two propellers each hooked up to their own transceivers. I am trying to do a simple two way communication. I have the BS2 source files which I used as a reference (BS2 code in notes of spin code). I have both propellers transfer and receiver data fine but for some reason when the data is received it is gibberish. I know that the transceivers work because I just used them on two of my BS2 stamps but they are not working for my Propellers though. If someone could take a look at my code I would really appreciate it.

There are two small LED's on the transceivers. One blinks when transferring data the other blinks when receiving data. When transmitting the LED's on both transceivers blink and so I assume they work fine, and when receiving data both transceiver's LED's also work. This has been driving me nuts for the last several hours!

I just starting playing with the Propellers two weeks ago so it may be a very simple mistake. I have attached all of my code and a read me file so it should be very easy to debug.

Thank you in advance,
Aaron Klapheck


03-30-2009, 10:41 PM
I have had the same problem for my propeller and radio reciever+transmitter. I put a serial LCD at one end and a propeller at the other end and when I hooked up the reciever to the LCD it started displaying jibberish before I even turned on the propeller! I then plugged it into a Basic Stamp displaying the input at the Debug terminal and into a speaker. I recieved identical jiberish on the debug and a drumming sound on the speaker. I believe that interference is causing it and I believe the same is happening to you. Is there a built in anntena, or do you have on an external?

Toys are microcontroled.
Robots are microcontroled.
I am microcontrolled.

04-01-2009, 04:15 AM
Hi Klap,

Attached is a program that I wrote for a mechatronics lab course that I taught last year. Every workstation had a Propeller chip wired up to a Parallax/ RF Digital 27985 912MHz serial RF transceiver module. The idea was that students could set 4 DIP switches (connected to pins 0-3) to select a workstation #·to send a message to and select one of·4 other DIP switches (connected to pins 4-7) to select a predetermined text message (up to 32 characters). Although this wireless protocol was fairly crude, it allowed lots of transceivers to share the same frequency and since each transmission only lasted about 27ms·crosstalk was extremely rare.

Now that I have more experience with the Propeller, I have been thinking about reworking this program so that it·can use the keyboard object·so that users can·type in custom text messages in realtime.·I might have some time to work on this "instant messenger"·program over the summer and post an object on the Propeller OBEX when it is finished. However, since Parallax seems to have stopped carrying these particular RF tranciever modules, I'm not sure·that·there would be much interest. For now, I hope that this code helps to point you in the right direction. Have fun!


04-01-2009, 12:29 PM
Thanks for your post. I used it but could not get it to work as well. If there is anyone who can find an error with my code I would really appreciate it. My program is very simple and should take no time at all to debut (maybe 15 minutes at the most if you have experience with RF transceivers).