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CC1310: Legacy application (TX only)

Scot Cowley
Intellectual 816 points
Part Number: CC1310
Other Parts Discussed in Thread: CC1101, , CC1070

Hi,

I have a requirement for a legacy transmit only RF project. Previously a CC1101 in asynchronous transfer mode

"Asynchronous transfer is included in the CC1101 for backward compatibility with systems that are already using the asynchronous data transfer"

The CC1101 would have it's GDO pin placed into asynchronous serial mode/direct mode which would allow a high or low data input on the GDO to control the TX signal. This is done manually at a data rate of 33.3khz.

The receiver hardware will not change but must support the CC1310 operating in the equivalent mode.

Would this be possible on the CC1310?

Kind Regards,

Scot

  • 0
    TI__Guru**** 317180 points
    For a TX only it should not be required to use transparent mode since you can place whatever you want to send in the TX buffer as part of the payload.

    What was the reason transparent mode was used on the CC1101?
  • 0 in reply to TER
    Intellectual 816 points
    It was used due to a legacy cc1070 (chipcon) project. This would be the second project keeping the legacy going.

    There were some interesting choices made which makes it hard to follow a payload format.

    Preamble - 30 bits (non manchester)
    Data - 28 bytes (manchester)
    Postamble - 3 bits (non manchester)

    OOK @ 33.3 kbps.
  • 0 in reply to Scot Cowley
    TI__Guru**** 317180 points
    The OOK patch for CC1310 supports up to 20 kbps. The limitation is mainly in RX. I haven't done any tests to see how high datarate it's possible to get in TX. Could you give an indication on the volume? (if you don't want to share it openly, send me a friend request)

    For the packet format I don't see an issue here since the manchester/ non manchester could be done in software on the CC1310.
  • 0 in reply to TER
    Intellectual 816 points
    Currently 10000-12000 per annum.

    Are you able to stipulate non manchester and manchester for different sections of the packet (like the preamble vs the data) in a single packet, also are you able to do postamble. I didn't see anything in the technical reference manual?

    Is there a way to disable the packet handling completely and directly control the TX data?
  • 0 in reply to Scot Cowley
    TI__Guru**** 317180 points
    Manchester a coding where 2 bits represent 1 bit. For the manchester section you can have a function converting the wanted data to manchester.

    For the existing product, is the bit length the same for manchester and non manchester?
  • 0 in reply to TER
    Intellectual 816 points
    Preamble - 30 bits (non manchester)
    Data - 224 bits (manchester)
    Postamble - 3 bits (non manchester)
  • 0 in reply to Scot Cowley
    TI__Guru**** 317180 points
    Maybe I didn't phrase my question properly. I was asking about the bit period length (how long time does one bit take) for manchester and non manchester in the legacy product?
  • 0 in reply to TER
    Intellectual 816 points

    The data is sent at 33.3kbps and the pre/postamble is sent at 16.7kbps (half).

  • 0 in reply to Scot Cowley
    TI__Guru**** 317180 points
    Then it could be required to code each re/post amble bit as '1' > '11' to get everything correct on the air. The fastest would probably be to do some quick trial and error and compare the resulting datastream with the legacy product.
  • 0 in reply to TER
    Intellectual 816 points

    I've investigated a bit more and I can't seem to find a way to modify the preamble to something specific (besides repeating 10 or 01) or to disable it.

    Here is the legacy comms:

    Preamble: 110011001100110011010101010101 (30 bits)
    Sync word: None
    Data: 24 bytes (manchester)
    CRC: 4 bytes (manchester)
    Postamble: 010 (3 bits)

    Is there a way to override some of the functions?
    Also can the sync word be disabled?

    I have a launchpad CC1310.

    Edit: To add. The only way I think I can do it on the CC1310 is to set the preamble to a single bit, and the sync word to 29 bits (if an odd number is allowed).

  • 0 in reply to Scot Cowley
    TI__Guru**** 317180 points

    To get a 0xCC preamble, see 

    What you can do is to set the sync word as part of the preamble (or payload). In TX, what matters is to get the wanted bit stream on the air and if the data is called preamble, sync or payload in the radio does not matter. 

  • 0 in reply to TER
    Intellectual 816 points
    So the only solution I see is to set the preamble to 1 bit and the sync word to 29 bits. Then do the data as usual.

    I think I can work around the post amble as well.

    Thanks for the assistance TER.