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CC1200: Minimum intervention via SPI to be able to send and receive data

roty
Prodigy 145 points
Part Number: CC1200

I have been told by TI Support to ask my question here in the forum.


We plan to use CC120x wireless devices in a new project. From the RF point of view it
looks perfect. However, I have a question about the SPI connection in advance , because
we intend to use a FPGA instead of a MCU to control the device.
I would like to know the minimum intervention via SPI to be able to send and receive data.

We have to transmit and receive a fixed number of bytes (e.g. 24). A device normally
just sends a data packet and the receiver just receives these packets. Only occasionally
data flow is in the opposite direction.

Provided the RX and TX FIFO full/empty state is routed to a GPIO pin, is the device able to
start data transmission automatically if the payload has been written to the TX-FIFO?
Can next transmission easily be started again just by writing next data packet to the TX FIFO?
Same thing with the receiver. Is the RX able to get new packets right after reading out RX-FIFO?

I appreciate any information .

Thanks

 

  • 0
    TI__Guru* 79491 points

    The basic steps to send and receive data is the following:

    Reset the device (SRES)
    Configure the device (Get the register settings needed from SmartRF Studio)

    TX:
    Write data to TX FIFO
    Send STX strobe
    Wait for an interrupt indicating that the packet has been sent

    With default settings from SmartRF Studio, the TXOFF_MODE = IDLE, meaning that the radio will go back into IDLE after a packet has been sent.

    It is possible to change TXOFF_MODE to TX. Then the radio will stay in TX (sending preamble) after a packet has been sent. As soon as you start writing new data to the TX FIFO, the radio will start to transmit the sync word (given that the programmed number of preamble has been sent) and then it starts sending the data in the TX FIFO again.

    Keeping the radio in constant TX will save you the STX strobe commands between packets, but you will possible increase the power consumption significantly unless you are planning to send the packets back-to-back anyway (main purpose of setting TXOFF_MODE to TX) .

    For RX, normal operation is to Strobe SRX, wait for an interrupt saying that the complete packet has been received, and then read the RX FIFO, before strobing RX again. In RX you can use RXOFF_MODE. You then do not have to strobe SRX over again, but you must make sure that you read out the current packets fast enough so that you do not get an RXFIFO_OVERFLOW when your next packet is received.

    Siri

  • 0 in reply to Siri
    Prodigy 145 points
    Thanks a lot for the detailed description.

    "It is possible to change TXOFF_MODE to TX. Then the radio will stay in TX (sending preamble) after a packet has been sent" .
    Does it mean the transmitter always occupies the channel if in TX mode? I assume yes.

    Thank you .

    Regards

    Robert
  • 0 in reply to roty
    TI__Guru* 79491 points
    That is correct.

    Siri