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CC1200: Setting RF Parameters from Smart RF Studio 7

Scott Morrison1
Prodigy 110 points
Part Number: CC1200
Other Parts Discussed in Thread: CC-DEBUGGER, CC2511

Hi there,

I was wondering if all of the parameters I would need to set a cc1200 to 455Mhz, 4.8ksps, 1.2khz deviation, 4FSK etc. is handled by the onboard MARC or is a separate microprocessor is definitely required.

When connected to the Smart RF Studio through the CC-Debugger, are all of the registers set and saved that way, or is there another programming portion to setting things up?

I'm trying to iron out how easy it would be move to this chip from another I've been working with that is an MCU+RF chip.

Thanks,

Scott

  • 0
    TI__Guru**** 317180 points

    If you want to make a board with CC1200 you would need a MCU. 

    As can be seen from the UserGuide, a MCU is needed to do the following:

    - Issue the command strobes to set CC1200 in the wanted state (STX, SRX etc) 

    - Set the wanted register settings. The registers loose the value after a power cycle and needs to be set from a MCU

    - Packet handling. The MCU has to write/ read from the FIFO the data that should be on the air. 

    The CCDebugger is basically a CC2511 that convert USB to SPI and that does the steps listed above controlled from a PC. 

    See the software examples on how to do the various steps from a MCU. 

  • 0 in reply to TER
    Prodigy 110 points

    Good to know!

    So the MARC 16-bit processor onboard is only for timing and power modes?


    Mostly what I've been looking for is a chip that can set and hold parameters - which I think we established in the spring is an MCU+RF system on board solution - that can handle 4(G)FSK in a transparent configuration.

    I have data coming from an external source that pre-packetizes the data, so transparent mode is a requirement.

    What drew me to the cc1200 was the line in the data sheet that specifically references moving 9.6kbps in a 12.5khz channel. But I don't have space in my design to add an external MCU - my board is already larger than I'd like at 2cm x 2.8cm.

    If you know of any other Ti chips that would meet my above criteria I'd definitely love to know about them.

    Thanks,

    Scott

  • 0 in reply to Scott Morrison1
    TI__Guru**** 317180 points

    MARC should be viewed as a deterministic state machine that controls how the chip moves from one state to the next. 

    As far as I know non of our chips are able to handle 4(G)FSK in transparent mode since only one pin is used as input/ output. 

    Could you elaborate a bit on "I have data coming from an external source that pre-packetizes the data, so transparent mode is a requirement." Since you require a very small board, where does the data com from, why is the system made like this? Is this for TX, what about RX? 

    It could be possible to mount the MCU on the opposite layer than the RF chip to make a small form factor.  

  • 0 in reply to TER
    Prodigy 110 points

    Understood, that makes more sense for needing an external MCU then.

    Without getting into proprietary details, the RS485 data is being generated and packetized to be sent hardwired to the end unit. What I am working on is removing the hardwiring.

    The data is not constant or clocked, and is also delay sensitive so the less processing of the data the better.

    So far I've had pretty good success with passing the handled RS485 data to a GPIO pin to be modulated and transmitted, but the chip I am currently using is capped at 2FSK when dealing with external data in this way. This has my Tx BW larger than the standard 12.5khz channel for a licensable frequency because the data is fixed at 9600 baud (9.6kbps) and using Carson's Rule the BW is approximately 28.8khz. Whereas 4FSK would bring my BW down to 12khz.

    The data is directional only, so the data generator is on the Tx side where form factor is not an issue - it's the Rx side that is truly size sensitive.

    I might have room for an MCU on the opposite side, but I was hoping to avoid more bottom layer components if at all possible - again for form factor on the Rx side.

    Multiple i/o pins are required for 4(G)FSK? Why is that?

  • 0 in reply to Scott Morrison1
    TI__Guru**** 317180 points

    For transparent mode in RX you get out if the deviation is positive or negative (non processed raw data). For 4-(G)FSK, you would need two pins to give information for one bit since the deviation could be over a given threshold, between the threshold and 0 and the same on the negative side. 

    "Synchronous Serial Mode" support 4-(G)FSK and in theory you can skip the sync word but you would need some preamble. Since this is RS-485, I assume that you only have a start and stop bit? 

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