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

Prodigy 30 points

Replies: 3

Views: 51

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);


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

3 Replies