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CC1125: Switch to the optional 32KHz clock input seems impossible so far...

George LIAKOPOULOS
Prodigy 180 points
Part Number: CC1125

Hello forum, 

Hopefully I will not spend much of your time since my problem sounds small but I am struggling to find clear instructions in the datasheet. We are using a CC1125 with Sniff Mode (eWOR) enabled, running with the internal crystal. The register configurations are listed below. We want to stop using the internal crystal and instead we are using GPIO3 of CC1125 in order to input a 32KHz external clock. So far, we cannot get the radio to work by modifying the following 4 registers which seem to be the only ones impacting the selection of the crystal used according to the datasheet unless I have missed something. Any help is more than welcome… 

Changes to register values in order to switch to external crystal (according to user guide/datasheet):

IOCFG3 = 0x30 (GPIO3_CFG = 48)

EXT_CTRL = 0x02 (EXT_32K_CLOCK_EN = 1)

WOR_CFG0 = 0x21 (RC_PD = 1 and DIV_256HZ_EN =1) also tried with (DIV_256HZ_EN =0)

 

 Register values with default, working configuration (using internal clock):

{ CC112X_IOCFG3, 24 }, // LNA/PA

{ CC112X_IOCFG2, 26 }, // RX0TX1

{ CC112X_IOCFG1, 0xB0 },

{ CC112X_IOCFG0, 0x06 },  // SYNC RXTX

{ CC112X_SYNC_CFG0, 0x14 },

{ CC112X_SYNC_CFG1, 0x0B },

{ CC112X_PREAMBLE_CFG1, 0x34 },  // 0x34->30bytes preamble, 0x30-> 24bytes preamble, 0x2C->12bytes preamble, 0x28->8bytes preamble  - If you change this update the WOR settings too!

{ CC112X_DEVIATION_M, 0xA3 },

{ CC112X_MODCFG_DEV_E, 0x0A },

{ CC112X_DCFILT_CFG, 0x1C },

{ CC112X_FREQ_IF_CFG, 0x33 },

{ CC112X_IQIC, 0xC6 },

{ CC112X_CHAN_BW, 0x10 },

{ CC112X_MDMCFG0, 0x05 },

{ CC112X_MDMCFG1, 0x80 | 0x40 | 8 | 6 | 0 },

{ CC112X_AGC_GAIN_ADJUST, -77 },

{ CC112X_SYMBOL_RATE2, 0x3F },

{ CC112X_SYMBOL_RATE1, 0x75 },

{ CC112X_SYMBOL_RATE0, 0x10 },

{ CC112X_AGC_REF, 0x20 },

{ CC112X_AGC_CFG1, 0xA0 },

{ CC112X_FIFO_CFG, 0x00 },

{ CC112X_SETTLING_CFG, 0x03 | 0x18 },

{ CC112X_FS_CFG, 0x12 },

{ CC112X_PKT_CFG0, 0x0 },

{ CC112X_PKT_LEN, NumberPacketBytes },

{ CC112X_IF_MIX_CFG, 0x00 },

{ CC112X_FREQOFF_CFG, 0x30 },

{ CC112X_FREQ2, 0x56 },

{ CC112X_FREQ1, 0xEC },

{ CC112X_FREQ0, 0x28 },

{ CC112X_IF_ADC0, 0x05 },

{ CC112X_FS_DIG1, 0x00 },

{ CC112X_FS_DIG0, 0x5F },

{ CC112X_FS_CAL0, 0x0E },

{ CC112X_FS_DIVTWO, 0x03 },

{ CC112X_FS_DSM0, 0x33 },

{ CC112X_FS_DVC0, 0x17 },

{ CC112X_FS_PFD, 0x50 },

{ CC112X_FS_PRE, 0x6E },

{ CC112X_FS_REG_DIV_CML, 0x14 },

{ CC112X_FS_SPARE, 0xAC },

{ CC112X_XOSC5, 0x0E },

{ CC112X_XOSC3, 0xC7 },

{ CC112X_XOSC1, 0x07 },

{ CC112X_RFEND_CFG1, 0x0f }, // end rx to idle

{ CC112X_RFEND_CFG0, 0x9 }, // end tx to into idle, term on bad & on CS

{ CC112X_WOR_CFG0, 0x00 },  // high resmode,

{ CC112X_WOR_CFG1, 0x08 },

{ CC112X_WOR_EVENT0_MSB, 0x6 },  // These may need tuning

{ CC112X_WOR_EVENT0_LSB, 0x3e /*116*/},

{ CC112X_PKT_CFG1, 0x45 },  // Whiten, CRC & Status on end - enable soon to add whitening

{ CC112X_PKT_CFG2, 0x10 },  // Enable LBT

{ CC112X_DEVIATION_M, 0xf8 },

{ CC112X_PREAMBLE_CFG1, 0x34 }, // 30bytes preamble

{ CC112X_MODCFG_DEV_E, 0x08 },

{ CC112X_CHAN_BW, 0x19 },

{ CC112X_SYMBOL_RATE2, 0x3f },

{ CC112X_AGC_REF, 0x20 },

{ CC112X_AGC_CS_THR, CC_MIN_SIGNAL },

{ CC112X_WOR_CFG0, 0x20 }, // 0x20->30,24,12,8bytes preamble

{ CC112X_WOR_EVENT0_MSB, 0x18 }, // 0x18->30bytes preamble, 0x13->24bytes preamble, 0x09->12bytes preamble, 0x06->8bytes preamble

{ CC112X_WOR_EVENT0_LSB, 0x8F }, // 0x8F->30bytes preamble, 0x90->24bytes preamble, 0x92->12bytes preamble, 0x3E->8bytes preamble

 

 

 

  • 0
    TI__Guru**** 317180 points
    At first glance the settings looks correct. When you write " So far, we cannot get the radio to work ", what do you mean? Could you elaborate a bit on what you see (or expect to see) ?
  • 0 in reply to TER
    Prodigy 180 points
    When two of my boards running with the "internal crystal" settings, both Tx and Rx works fine (meaning over the air messages are decoded correctly at both ends). In addition, having a DC analyser connected, I can observe the expected Sniff Mode operation with sleep time of approx 150ms with the expected power consumption.
    When I switch to "external crystal" settings, there is no communication between the modules. On the DC analyser I can see the attempts to Tx but nothing is received at the other side. In addition, the power graph looks odd since there is NOT sleep time! Instead, there is a 9ms periodicity signal constantly running and when I disconnect the external crystal, this signal goes down as well...
  • 0 in reply to George LIAKOPOULOS
    TI__Guru**** 317180 points
    I assume you have written the code for this on a custom board?

    I would like to test it on a TRXEB first I would need to write some code for testing.
  • 0 in reply to TER
    Prodigy 180 points

    Correct. I will not be able to share the entire project but I could give you snippets of code involving radio configuration or commanding.

    Much appreciated!

    Regards, George

  • 0 in reply to George LIAKOPOULOS
    TI__Guru**** 317180 points

    I started from the CC112x code examples: 

    I used the rx_sniff_mode (config 1)

    To get a 32 kHz clock I could use on the RX side I did the following change in the TX code:

    #define GPIO3                   0x36
    void main(void) {

    // Initialize MCU and peripherals
    initMCU();

    // Write radio registers
    registerConfig();

    //Setting GPIO3
    uint8 writeByte = GPIO3;
    cc112xSpiWriteReg(CC112X_IOCFG3, &writeByte, 1);
    
    // Enter runTX, never coming back
    runTX();
}

    On the RX side I did the following:

    #define GPIO3                   0x30
    void main(void) {

    // Initialize MCU and peripherals
    initMCU();

    // Write radio registers
    registerConfig();
    //Setting GPIO3
    uint8 writeByte = GPIO3;
    cc112xSpiWriteReg(CC112X_IOCFG3, &writeByte, 1);

    //Setting EXT_CTRL
    writeByte = 0x02;
    cc112xSpiWriteReg(CC112X_EXT_CTRL, &writeByte, 1);
    
    //Setting WOR_CFG0
    writeByte = 0x21;
    cc112xSpiWriteReg(CC112X_WOR_CFG0, &writeByte, 1);

    // Enter runRX, never coming back
    runRX();
}

    Comment out calibrateRCOsc();

    This looks like it works. 

    Looking on your code it looks like you have a double definition of GPIO3, it depends which line that is written when. 

  • 0 in reply to TER
    Prodigy 180 points

    Hello,

    Apologies for the late response but I was out of the office. Thank you very much for spending time on this matter. 

    Now, I have a couple of questions regarding the changes you applied and also about one of your comments.

    1. Why you have setup GPIO3 differently on Rx and TX? I assume you want to prove that you system works with a combination of internal and external clock right? If not then it is a bit confusing since we are planing to use external on both sides of our product.

    2. Can you please clarify your following comments "Looking on your code it looks like you have a double definition of GPIO3, it depends which line that is written when." Where is the double definition of GPIO3 in the list of registers I sent you? If you are referring to the following "{ CC112X_IOCFG3, 24 }, // LNA/PA" this is the default setting while running with the external clock but even then, GPIO3 is not used.

    3. Why you are commenting out calibrateRCOsc();?

    Regards

    George

  • 0 in reply to George LIAKOPOULOS
    TI__Guru**** 317180 points
    1) My objective was to show that the RX side worked with an external clock. I found that the easiest way to get an external 32 kHz clock was to use the TX side to generate it for me, hence the different settings.
    2) So when you use external clock you have not included this line: { CC112X_IOCFG3, 24 }, // LNA/PA?
    3) Since the RC OSC is powered down it makes no sense to try to calibrate it.
  • 0 in reply to TER
    Prodigy 180 points

    Hello,

    Thanks for the clarifications but unfortunately your suggestion still didn't help. I am tempted to try all your register settings on my hardware but I am worried in case I brick something.

    Do you have any other trouble shooting ideas?

    Regards

    George

  • 0 in reply to George LIAKOPOULOS
    TI__Guru**** 317180 points
    It's not possible to brick CC1125 since it looses it's setting when a reset is issued or the power is removed. My code worked in my end, have you tried this unmodified?