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CCS/CC1350: Calibration does not work while using LF_RCOSC

Fan_Zhang
Expert 4600 points

Part Number: CC1350
Other Parts Discussed in Thread: CC2650, CC2640

Tool/software: Code Composer Studio

Hi,

I am testing drift of internal LF_RCOSC, and than decide the calibration interval.

I am using CC1350 (reversion 2.1) launchpad.

I use empty example from SDK, and make following modifications.

(1). change the setting in ccfg.c to use LF_RCOSC as follow.

#ifndef SET_CCFG_MODE_CONF_SCLK_LF_OPTION
// #define SET_CCFG_MODE_CONF_SCLK_LF_OPTION 0x0 // LF clock derived from High Frequency XOSC
// #define SET_CCFG_MODE_CONF_SCLK_LF_OPTION 0x1 // External LF clock
// #define SET_CCFG_MODE_CONF_SCLK_LF_OPTION 0x2 // LF XOSC
#define SET_CCFG_MODE_CONF_SCLK_LF_OPTION 0x3 // LF RCOSC
#endif

(2). output 32k signal to IO as follow.

IOCPortConfigureSet(IOID_6, IOC_PORT_AON_CLK32K, IOC_STD_OUTPUT);
AONIOC32kHzOutputEnable();

(3). use both automatically and manually calibrations

besides automatic calibration, I also explicitly trigger RC oscillator calibration by calling PowerCC26XX_injectCalibration() every 500ms.

Finally, I test the output signal with a frequency spectrograph.

I test on two lauchpad, and the frequency of output signals are 32.693kHz and 32.678kHz.

The frequency drift more 2000 ppm.

In another test, I disable automatically calibration and comment out the explicitly trigger PowerCC26XX_injectCalibration(). The  frequency of the output signals remain the same. It seems the calibration is not working.

Can you help to explain this or point out the error in my test.

Thanks.

  • 0
    TI__Guru** 106705 points
    Hi Felix,

    Strictly speaking 32k RC oscillator calibration is only supported on CC2640 and CC2650. I believe it still should work on the CC1350, but it has not been tested.

    Which BLE Stack are you using? Are you following the exact steps in the application note: www.ti.com/.../swra499b.pdf ?

    Cheers,
    Fredrik
  • 0 in reply to Fredrik K
    TI__Expert 4600 points

    Hi, Fredrik,

    I did not use a BLE stack, but just did my test based on empty example in the SDK.

    I have read the application note you mentioned and go through the configuration chapter.

    Although I do not run a BLE stack in my test, I enable automatically calibration by setting ".calibrateRCOSC_LF = TRUE," in PowerCC26XX_Config PowerCC26XX_config, and manually trigger calibration by calling  PowerCC26XX_injectCalibration(). I think this should make calibration work.

    Please give your comment, Thanks.