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Cc1101 Asynchronous communication noise problem

Ab KJ
Prodigy 60 points

Other Parts Discussed in Thread: CC1101

We are trying to read an RF signal from  external  Door sensor(433 mHz).  I have used the application note of DN022 for configuring the cc1101 as ASK/OOK mode. We configured GDO0 PIN as data output pin. The CC11101 detect the sensor triggering , but the read bit pattern is always different. I was trying with different data rates on both the sensor and the CC1101 device, but the effect is same. The pin GDO0 by default is at logic level 1, but my sensor transmits start bit is also as Logic 1 , so we cannot identify the start bit correctly . This is also another problem.  

So my questions are

1. Why the PIN GDO0 is always high after we configured the CC1101 in asynchronous mode? . Can we change the logic level of PIN by default ?

2. Why MCU always collect different bit pattern from the sensor ? Is it because of noise effect ?

3. Why the CC1101 detect some junk values with out  sensor triggering?

I was trying to solve the issue for the last three days , but the result is not good.

Any help will be appreciated. 

  • 0
    Mastermind 8170 points

    1.) A wrapper is generally put around the data to give you the hooks to retrieve the data at the receiver.

    2 and 3.) With the use of a longer preamble (PKTCTRL1) and sync (SYNCn), setting their evaluation criteria higher, checking CRC, and by using a address (ADDR register) you can significantly reduce the number of false triggers which also means you will not receive incorrect data. In addition the wrapper placed around the data can give you yet another layer of data filtering.

  • 0 in reply to H Stewart
    Prodigy 60 points

    Thanks for the information, But unfortunately we have used a sensor module, which is not programmable. The total data sent by the sensor is 12 bits , we cannot add any preamble or sync word in front of the data. 

    Please send us the suggestions, we didn't  get any more reply from this forum. 

  • 0 in reply to Ab KJ
    TI__Guru**** 317180 points

    Most radios including CC1101 needs 2-3byte preamble + sync to receive a OOK signal. 12bit sounds like a very low amount of data. Do you have a spec for the sensor or are you just sampling the data to see what it sends?

  • 0 in reply to TER
    Prodigy 60 points

    Thanks for your expert answer. I have used the sensor from Chinese suppliers , the chip they have used is PT2262 , which is an encoder. They used the encoder plus simple transistor logic to transmit an  RF signal.  We don't have any option to add any preamble or Sync bytes. So that i have choose the asynchronous mode in CC1101.

    Please see the files, I have attached the sensor specs and the data sheets. 

    I plan to redesign the sensor with CC1101, but it is costly.

     Thanks in advance.