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CC1101: building a generic repeater

David Grenz
Prodigy 40 points
Part Number: CC1101

Hi,

I am searching for a 434/868 MHz generic repeater design. I am pretty new to all this RF stuff and apologize for asking stupid questions. The goal is to repeat signals from different, mainly home automation devices like temperature or window sensors to increase range and keep it compatible to a wider range of different devices with small effort.

I know that at least the modulation and frequency must be set right - but what about the baudrate for example? If I'd set it as fast as possible, it should be more compatible to several baudrates, because it would just receive multiple bits of the same source bit and send it the same way, so the original receiver cannot recognize any difference, is that right?

What about preamble and sync? Because it should just be a "stupid" repeater, I'd set MDMCFG2 / SYNC_MODE to 0 and disable it, correct?

And how would the repeater know when to repeat a signal? Would it make sense to start sending signals just above a specific RSSI value?

From the hardware I have some arduinos and would use the panstamp library. Do I need to use 2 CC101's for one repeater because receiving while sending is not possible?

Any thoughts on that would highly be appreciated!
Thanks!
David

  • 0
    TI__Guru**** 317180 points
    Making a generic repeater is a bit tricky.

    The "normal" way to use the chip is to have a known sync word and a known deviation/ datarate. If you don't know either you have to use Asynchronous mode (section 27 in the CC1101 datasheet) and do a lot of post processing in the MCU. The MCU should figure out if the received data is a valid signal that should be resent or noise.

    Sending and receiving at the same time with CC1101 is not possible. If you have 2 CC1101s you should still avoid sending on the same channel as you receive with the other one since you will block yourself.
  • 0
    Expert 1240 points
    Making a generic repeater is WICKED tricky.
    Designing either a full-duplex, half-duplex or simplex "store & forward" repeater gets real complex real fast as well.

    However, a simple 418/433MHz or 868/915MHz system can provide reliable coverage for most residences.
    You mostly need a good antenna on the central station/collector and properly designed antenna for the sensors/remotes.