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Very short Transmissions without preamble nor sync word on CC11XX

citizen
Expert 2770 points
Other Parts Discussed in Thread: CC1200, CC1120Hi, I would like to know if there are any implications when transmitting from a CC112X radio with Preamble Bytes set to 0 and Sync Word bytes also set to 0 ? These two options are available if you check the respective registers. I am trying to limit a select few dummy transmissions to less than about 2 bytes in total/dummy Tx. These transmissions are never meant to be received /decoded by anyone, but they basically "look good" to those who see them ... At the moment I am not seeing any transmissions when I set the Preamble =0, and Sync Word=0, with frame length = 1byte and no CRC nor other stuff. The radio does not seem to be sending any GDOX interrupts at the end of a Transmission as usually is the case when transmitting a small frame (one that has a preamble and a sync word and is meant to be received by somebody on the other end). So basically what gives with switching preamble and sync words completely OFF ? What is best way to detect an end of a very short transmission, presuming one has started a Tx straight away with the 1 byte data, and preamble + sync OFF ?? Is there anything special to be done really ? Thanks in advance for any good advice ... cheersM
  • 0
    TI__Mastermind 36375 points

    M MAR, 

    It is recommended to keep the SYNC word enabled as most of the timing inside the transceiver is based of the Sync word. That being said, on the CC1120 and CC1200 it is possible to disable the preamble and only transmit the Sync word, it is furthermore possible to set the packet length to 0 and disable the CRC generation. 

    I did that using SmartRF Studio and verified that the device transmitted the data using a spectrum analyzer. With the settings below the CC1200 only transmitted 11 bits of data per burst and those 11 bits where configurable by changing the values in the Sync word registers.

    Regards,
    /TA

    6114.cc1200_11bit_burst.xml 
    <?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE configuration SYSTEM "C:/Program Files (x86)/Texas Instruments/SmartRF Tools/SmartRF Studio 7/config/xml/configdata.dtd"[]>
<dcpanelconfiguration>
    <Devicename>CC1200</Devicename>
    <Description>Saved configuration data</Description>
    <registersettings>
        <Register>
            <Name>AGC_CFG0</Name>
            <Value>0x87</Value>
        </Register>
        <Register>
            <Name>AGC_CFG1</Name>
            <Value>0x51</Value>
        </Register>
        <Register>
            <Name>AGC_CS_THR</Name>
            <Value>0xec</Value>
        </Register>
        <Register>
            <Name>AGC_REF</Name>
            <Value>0x20</Value>
        </Register>
        <Register>
            <Name>ASK_CFG</Name>
            <Value>0x3f</Value>
        </Register>
        <Register>
            <Name>CHAN_BW</Name>
            <Value>0xa6</Value>
        </Register>
        <Register>
            <Name>DCFILT_CFG</Name>
            <Value>0x5d</Value>
        </Register>
        <Register>
            <Name>DEVIATION_M</Name>
            <Value>0xd1</Value>
        </Register>
        <Register>
            <Name>FIFO_CFG</Name>
            <Value>0x00</Value>
        </Register>
        <Register>
            <Name>FREQ1</Name>
            <Value>0x80</Value>
        </Register>
        <Register>
            <Name>FREQ2</Name>
            <Value>0x5b</Value>
        </Register>
        <Register>
            <Name>FREQOFF_CFG</Name>
            <Value>0x22</Value>
        </Register>
        <Register>
            <Name>FS_CAL0</Name>
            <Value>0x0e</Value>
        </Register>
        <Register>
            <Name>FS_CAL1</Name>
            <Value>0x40</Value>
        </Register>
        <Register>
            <Name>FS_CFG</Name>
            <Value>0x12</Value>
        </Register>
        <Register>
            <Name>FS_DIG0</Name>
            <Value>0xaf</Value>
        </Register>
        <Register>
            <Name>FS_DIG1</Name>
            <Value>0x07</Value>
        </Register>
        <Register>
            <Name>FS_DIVTWO</Name>
            <Value>0x03</Value>
        </Register>
        <Register>
            <Name>FS_DSM0</Name>
            <Value>0x33</Value>
        </Register>
        <Register>
            <Name>FS_DVC0</Name>
            <Value>0x17</Value>
        </Register>
        <Register>
            <Name>FS_PFD</Name>
            <Value>0x00</Value>
        </Register>
        <Register>
            <Name>FS_PRE</Name>
            <Value>0x6e</Value>
        </Register>
        <Register>
            <Name>FS_REG_DIV_CML</Name>
            <Value>0x1c</Value>
        </Register>
        <Register>
            <Name>FS_SPARE</Name>
            <Value>0xac</Value>
        </Register>
        <Register>
            <Name>FS_VCO0</Name>
            <Value>0xb5</Value>
        </Register>
        <Register>
            <Name>IF_ADC0</Name>
            <Value>0x10</Value>
        </Register>
        <Register>
            <Name>IF_ADC1</Name>
            <Value>0xee</Value>
        </Register>
        <Register>
            <Name>IF_MIX_CFG</Name>
            <Value>0x1c</Value>
        </Register>
        <Register>
            <Name>IOCFG2</Name>
            <Value>0x06</Value>
        </Register>
        <Register>
            <Name>IQIC</Name>
            <Value>0xcb</Value>
        </Register>
        <Register>
            <Name>MDMCFG0</Name>
            <Value>0x05</Value>
        </Register>
        <Register>
            <Name>MDMCFG1</Name>
            <Value>0x40</Value>
        </Register>
        <Register>
            <Name>MDMCFG2</Name>
            <Value>0x0c</Value>
        </Register>
        <Register>
            <Name>MODCFG_DEV_E</Name>
            <Value>0x00</Value>
        </Register>
        <Register>
            <Name>MODEM_STATUS1</Name>
            <Value>0x10</Value>
        </Register>
        <Register>
            <Name>PARTNUMBER</Name>
            <Value>0x20</Value>
        </Register>
        <Register>
            <Name>PARTVERSION</Name>
            <Value>0x11</Value>
        </Register>
        <Register>
            <Name>PA_CFG1</Name>
            <Value>0x3f</Value>
        </Register>
        <Register>
            <Name>PKT_CFG1</Name>
            <Value>0x01</Value>
        </Register>
        <Register>
            <Name>PKT_CFG2</Name>
            <Value>0x00</Value>
        </Register>
        <Register>
            <Name>PKT_LEN</Name>
            <Value>0x00</Value>
        </Register>
        <Register>
            <Name>PREAMBLE_CFG0</Name>
            <Value>0x8a</Value>
        </Register>
        <Register>
            <Name>PREAMBLE_CFG1</Name>
            <Value>0x00</Value>
        </Register>
        <Register>
            <Name>SYMBOL_RATE0</Name>
            <Value>0x10</Value>
        </Register>
        <Register>
            <Name>SYMBOL_RATE1</Name>
            <Value>0x75</Value>
        </Register>
        <Register>
            <Name>SYMBOL_RATE2</Name>
            <Value>0x3f</Value>
        </Register>
        <Register>
            <Name>SYNC_CFG1</Name>
            <Value>0x2b</Value>
        </Register>
        <Register>
            <Name>XOSC1</Name>
            <Value>0x03</Value>
        </Register>
        <Register>
            <Name>XOSC5</Name>
            <Value>0x0e</Value>
        </Register>
    </registersettings>
    <dcpanel>
        <Property role="44" name="m_chkRegView">2</Property>
        <Property role="44" name="m_chkRfParameters">2</Property>
        <Property role="37" name="m_tabUserMode">1</Property>
        <Property role="33" name="m_easyModeSettings">-1</Property>
        <Property role="33" name="m_typicalSettings">-1</Property>
        <Property role="37" name="m_testFuncPanel">2</Property>
    </dcpanel>
    <rfparameters>
        <Property role="46" name="m_cmbFrontends">0</Property>
        <Property role="44" name="m_chkHGMorBYP">2</Property>
        <Property role="46" name="m_cmbEmRevs">-1</Property>
        <Property role="46" name="Xtal frequency">40.000000</Property>
    </rfparameters>
    <conttx>
        <Property role="45" name="m_rbtModulated">1</Property>
        <Property role="45" name="m_rbtUnmodulated">0</Property>
        <Property role="46" name="m_cmbDataFormat">-1</Property>
        <Property role="44" name="m_chkFreqSweep">0</Property>
        <Property role="44" name="m_chkChanSweep">0</Property>
    </conttx>
    <contrx>
        <Property role="46" name="m_cmbDataFormat">-1</Property>
        <Property role="44" name="m_chkAutoScroll">2</Property>
    </contrx>
    <packettx>
        <Property role="42" name="m_edtPktLength">0</Property>
        <Property role="42" name="m_edtPacketCount">100</Property>
        <Property role="42" name="m_edtPacketCountEsy">100</Property>
        <Property role="42" name="m_edtPacketData">f4 </Property>
        <Property role="42" name="m_edtAccessAddress"></Property>
        <Property role="44" name="m_chkAddSeqNbr">0</Property>
        <Property role="44" name="m_chkInfinite">2</Property>
        <Property role="44" name="m_chkInfiniteEsy">2</Property>
        <Property role="45" name="m_rbtRandom">1</Property>
        <Property role="45" name="m_rbtText">0</Property>
        <Property role="45" name="m_rbtHex">0</Property>
        <Property role="44" name="m_chkAdvanced">2</Property>
        <Property role="46" name="m_cmbLengthConfig">0</Property>
        <Property role="42" name="m_edtFixedPktLength">0</Property>
        <Property role="42" name="m_edtBitLength">0</Property>
        <Property role="20" name="m_grp802154g">0</Property>
        <Property role="42" name="m_edt802154gPktLength"></Property>
        <Property role="45" name="m_rbt802154g2BCrc">1</Property>
        <Property role="45" name="m_rbt802154g4BCrc">0</Property>
        <Property role="44" name="m_chk802154gWhitening">2</Property>
        <Property role="44" name="m_chkFEC">0</Property>
        <Property role="46" name="m_cmbPreambleWord">0</Property>
        <Property role="46" name="m_cmbPreambleCount">0</Property>
        <Property role="42" name="m_edtSync3">93</Property>
        <Property role="42" name="m_edtSync2">0b</Property>
        <Property role="42" name="m_edtSync1">51</Property>
        <Property role="42" name="m_edtSync0">de</Property>
        <Property role="42" name="m_edtAddress"></Property>
        <Property role="44" name="m_chkAddress">0</Property>
        <Property role="42" name="m_edt802154gHeader">0x181e</Property>
        <Property role="46" name="m_cmbSyncMode">1</Property>
        <Property role="52" name="m_spnPktInterval">100</Property>
        <Property role="44" name="m_chkDefPktInterval">2</Property>
    </packettx>
    <packetrx>
        <Property role="42" name="m_edtPacketCount">100</Property>
        <Property role="42" name="m_edtPacketCountEsy">100</Property>
        <Property role="42" name="m_edtAccessAddress"></Property>
        <Property role="44" name="m_chkInfinite">0</Property>
        <Property role="44" name="m_chkInfiniteEsy">0</Property>
        <Property role="46" name="m_cmbViewFormat">0</Property>
        <Property role="44" name="m_chkSeqNbrIncluded">2</Property>
        <Property role="42" name="m_edtDumpFile"></Property>
        <Property role="44" name="m_chkAdvanced">0</Property>
        <Property role="44" name="m_chk802154gMode">0</Property>
    </packetrx>
    <commandpanel>
        <Property role="44" name="m_chkInsertLength">0</Property>
        <Property role="42" name="m_edtTxFifo"></Property>
        <Property role="42" name="m_edtRxFifo"></Property>
        <Property role="46" name="m_cmbInstrInput">-1</Property>
    </commandpanel>
    <packetRxSniffMode>
        <Property role="42" name="m_edtPreambleLength">4</Property>
        <Property role="42" name="m_edtCarrierSenseThreshold">-90</Property>
        <Property role="45" name="m_rbtRssi">1</Property>
        <Property role="45" name="m_rbtPreamble">0</Property>
    </packetRxSniffMode>
</dcpanelconfiguration>

       

  • 0 in reply to TA12012
    Expert 2770 points
    Hi, Thanks for your quick reply. That seems to do the trick. I now have useless, very short packets being sent now, but they "look good" anyways ;-) I was just wondering in terms of measured packet length I get something longer than I calculated. In other words, I measure about 2ms at 10kb/s when I actually calculated 1,1ms (1/10000 * 11 bits). The CRC generation and preamble is not activated as you suggested, to keep Tx duration to minimum, so I'm seeing longer packets than expected. Is this what you have seen when measuring, say with a communications / transmitter analyser ?? The amp ramp-up/down time should not be adding that much to the overall packet Tx time, or am I missing something else that is being sent with the 11-bit SYNC word ?!? Just wondering ... Regards, mik