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CC110L AIR Module

ROM_Jamie
Intellectual 810 points
Other Parts Discussed in Thread: CC110L

I'm using a TM4C123G to develop this project but I'm not certain I wouldn't be better off posting this under MSP430.

I'm trying to get a handle on the transmit time for a single packet.

When I build a packet I do a burst write to the Tx FIFO, first byte = length (34), second byte = address, next 32 bytes = payload. After the data is in the FIFO I send the STX command strobe to begin transitioning to Tx. Once in Tx I wait for underflow to indicate the buffer has emptied.

I've been trying to configure the CC110L to minimize the time it's taking to get into TX from IDLE.

i.e. I send the STX, and there is a ~1.4ms delay before the GDO0 pin goes high (indicating the sync word has sent / data is being transmitted)

I was able to drop this down to ~0.7ms between STX and sync byte by disabling the auto-calibration (MCSM0.FS_AUTOCAL = 00)

I'm having trouble finding any way to decrease that time further, i.e. the time to transition from IDLE -> FS_WAKEUP -> SETTLING -> TX

Has anyone come to the practical limit here? These times are based on the 100kbaud data rate I'm using, I intend to do some testing tomorrow to see if changing the data rate significantly affects the delay.

  • 0
    TI__Guru**** 244400 points
    Hello Jamie,

    Do you mean 100K Baud rate on the SSI Interface? If yes, then increasing the baud to the maximum of TM4C output or CC110L input can accept will have an effect for the time it takes to move from one state to another.,

    Regards
    Amit
  • 0 in reply to Amit Ashara
    Intellectual 810 points

    No, the SSI interface is configured as

    MAP_SSIConfigSetExpClk(CC110L_SSI_BASE,     // ssi module base address
                       g_ui32SysClock,      // clock rate to the ssi module
                       SSI_FRF_MOTO_MODE_0, // data transfer protocol
                       SSI_MODE_MASTER,     // mode of operation
                       5000000,             // clock rate
                       8);                  // bits per frame

    which is much faster than the rate the radio is transmitting data.

    The RF data rate is configured in registers MDMCFG4.DRATE_E and MDMCFG3.DRATE_M, it is also called the "user specified symbol rate"

    My 100kBaud value is defined using

    MDMCFG4 = 0xF8

    MDMCFG3 = 0x93

  • 0 in reply to ROM_Jamie
    Intellectual 810 points
    Increasing the the data rate to 250kBaud has dropped the delay to ~300us

    I'm not sure if the change in transition time can be solely attributed to the increase in preamble transmission.
  • 0 in reply to ROM_Jamie
    TI__Guru**** 244400 points
    Hello Jamie

    Doesn't the CC110L specify the total time from IDLE to TX as a parameter? You may want to check with forum for the same.

    Regards
    Amit