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CC1125: Unmodulated CW mode TX to IDLE ends in TX_END State

Prodigy 40 points

Replies: 6

Views: 121

Part Number: CC1125

I have two frequency variants of a rf board with a CC1125. One variant for the 868 MHz band and one for the 434 MHz band. 

The same firmware runs on each variant of the board, just parameters affecting the frequency band are configured differently. 

When leaving unmodulated CW mode I observe different behaviour for the 433 and for the 868 MHz frequency band. 

An IDLE strobe leads to IDLE mode in the 868 board. On the 433 variant the CC1125 ends up in MARC_STATE = 0x34 (--> TX_END).

Modulated CW mode works as expected on both variants, so does regular packet transmission. 

I'm entering the modulated/unmodulated CW mode using this code:

    // random mode, send random data using  pn9 generator , TXLAST != TXFIRST
    writeByte = 0x02; 
    trxCC1125WriteReg(CC112X_PKT_CFG2, &writeByte, 1); 
    // infinite packet length mode
	writeByte = 0x40; 
    trxCC1125WriteReg(CC112X_PKT_CFG0, &writeByte, 1); 
	    
    // CFM enabled, write frequency word directly (custom frequency modulation enable)
    if (modulated) {
        writeByte = 0x00; // modulated carrier
    } else {
        writeByte = 0x01; // unmodulated carrier
    }
    trxCC1125WriteReg(CC112X_CFM_DATA_CFG, &writeByte, 1); 	// 0x00 = modulated 0x01 = Unmodulated

    // for continuous transmission TXFIRST != TXLAST
    // should also work if one byte is written to fifo.
    writeByte = 0; 
    trxCC1125WriteTxFifo(&writeByte, 1);

    trxCC1125CmdStrobe(CC112X_STX);

Any hints from TI experts on this one? Any help is appreciated.

  • It is not a device defect. It systematically happens on all 433 modules I tested for unmodulated CW. 

  • In reply to Dominik Elberskirch1:

    Hi,

    I will assign an expert to comment.

    Regards,

     

    I am out of the office and plan to be back on the 29 July.
    If your question is not answered in the next few days, I will kindly ask you to open a new thread using the “Ask a related question” button.
    Have a nice summer!

    - Clément

  • In reply to Clément:

    Thanks alot!

  • Guru 271935 points

    In reply to Dominik Elberskirch1:

    This has unfortunately taken some time due to one of the experts on CC1125 code being out ill this week. 

    Do you have code for what you are doing that we can run on a TRXEB?

    If not, what is the difference between the 433 Mhz and the 868 MHz code? I can't see anything from how the chip is designed that could explain that the chip behave differently for two different frequencies. 

    Does this only happens if you go from 868 MHz to 433 Hz? What about 869 MHz or 915 MHz etc? 

     

  • Guru 271935 points

    In reply to TER:

    Do you have any further feedback on this case or have you solved this? 

     

  • In reply to TER:

    TER

    Do you have any further feedback on this case or have you solved this? 

    I now have a version, where I don't see this behaviour. I'm currently trying to isolate the specific change, which causes the issue. 

    There is not difference between how the code works for 868 and 434. The settings for frequency are calculated based on the formula in the user guide and using the correct setting of the Lo Divider. 

    I'll give feedback here once I've sorted this.

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