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IWR6843: Chirp limits and timing

martin
Prodigy 70 points
Part Number: IWR6843
Other Parts Discussed in Thread: MMWAVE-STUDIO, AWR1243

Hi,

I try to find out the limit of the IWR6843 Chip but I can't find a documentation that gives me the limit for the chirp parameter e.g. slope. In the following document I found some hints

but I can only make suggestions of the limits.

In this document

they mentioned a chirp timing parameter configuration calculator utility in Radar Studio application available as part of the DFP Packages but I can't find this tool in the Package.

The Doxygen documentation seems also not very helpful. Is there a documentation of the RF-parameters with their limits?

Also for my application I like to know/control the time when a chirp (or a sequence of chirps) starts in my application as good as possible. Is there a way to control the start of the chirp from the application exactly?

Regards,

Martin

  • 0
    TI__Mastermind 30405 points

    Hi Martin,

    1. I try to find out the limit of the IWR6843 Chip but I can't find a documentation that gives me the limit for the chirp parameter e.g. slope. 

    The chirp parameters such as idle time, ramp slope, ADC start time etc are part of profile configuration API (rlSetProfileCfg) which is part of the mmWaveLink sensor control functions. You can find the detailed API list in the mmWaveLink doxygen documentation as given below:

    Top level page: C:/ti/mmwave_sdk_03_00_00_08/packages/ti/control/mmwavelink/docs/doxygen/html/index.html.

    Under Modules, Click on the Sensor -> rlSetProfileConfig ->  rlProfileCfg_t to get the detailed parameter list including the limits as shown in the snapshot below. You can follow the same structure for other APIs and their parameters.

    C:/ti/mmwave_sdk_03_00_00_08/packages/ti/control/mmwavelink/docs/doxygen/html/structrl_profile_cfg__t.html

    2. Also for my application I like to know/control the time when a chirp (or a sequence of chirps) starts in my application as good as possible. Is there a way to control the start of the chirp from the application exactly?

    At a low level (i.e. mmWaveLink level), the rlSensorStart function starts the chirping. From an application level, the MMWAVE_start function applies the configuration and invokes this function. Look at the following call sequence in the SDK out of box demo (i.e. mmw demo)

    C:\ti\mmwave_sdk_03_00_00_08\packages\ti\demo\xwr68xx\mmw\main.c

    -->  MmwDemo_startSensor()

          --> MMWave_start()

                --> MMWave_startLink()

                      --> rlSensorStart()

    3. a chirp timing parameter configuration calculator utility in Radar Studio application available as part of the DFP Packages but I can't find this tool in the Package.

    The chirp/ramp timing calculator tab is available in MMWAVE-STUDIO as detailed in the following thread:

    AWR1642BOOST: Understanding changes in "TX start time" and "ADC valid start time"

    Finally, the following thread is also a good resource for understanding the profile configuration parameters:

    IWR1443: profile parameter guidelines

    Please mark this thread resolved if your questions were answered.

    Thanks

    -Nitin

     

  • 0 in reply to Nitin Sakhuja
    Prodigy 70 points

    Hi Nitin,

    that answered most of my questions.

    I understood that the chirp starts after sending the rlSensorStart() command. But how long does it take from sending the comman until the chirp starts and more important is this time delay fix or is there a variation?

    Regards,

    Martin

  • 0 in reply to martin
    TI__Mastermind 30405 points
    Hi Martin,

    Please allow me a couple of days to find this information.

    Thanks
    -Nitin
  • 0 in reply to Nitin Sakhuja
    TI__Mastermind 30405 points
    Hi Martin,

    I'm still looking for information on this topic and will get back to you ASAP. Could you provide some information on your use-case and how does it relate to the exact timing requirement? Thanks for your patience.

    Regards
    -Nitin
  • 0 in reply to Nitin Sakhuja
    TI__Mastermind 30405 points
    Hi Martin,

    We do not have these specific measurements on IWR6843 however, we do have sample time measurements based on sending the rlSensorStart command from the SPI interface on an AWR1243 device (which is the Front End only device for automotive markets). It took about 450us from sending the command over SPI to getting the response back.

    On IWR6843 using the mmWave SDK, after calling the rlSensorStart API, the mmwavelink functions form the sensor start message and write it to the Mailbox memory for the Radar SubSystem (i.e. BSS). We have not profiled this but it should be quicker than the above.

    You can get the numbers by instrumenting the following functions in the mmwavelink unit test:

    File: ti\control\mmwavelink\test\xwr68xx
    Functions: MmwaveLink_sensorStart, Mmwavelink_frameInterrupCallBackFunc

    Regards
    -Nitin
  • 0 in reply to Nitin Sakhuja
    Prodigy 70 points

    Hi Nitin,

    thanks for the answer. If I understood correct the AWR1243 start the ramp before sending the acknowledgment back over the SPI Interface. I try to draw a simplified diagram

    So T_Ack is <= 450 us. I need to know, when the chirp sequence starts. It is okay for the application, that these communication take 450 us. But do you know the jitter of this timing. This should be << T_Ack. Correct? So for my application the jitter of the Time T_com1 + T_startSeq is critical and should be low. So if the jitter of T_Ack is low this jitter should be also low. Do you have here some numbers?

    Regards,

    Martin

  • 0 in reply to martin
    TI__Mastermind 30405 points
    Hi Martin,

    We have not measured Jitter in this timing but I don't have a reason to believe that it would vary too much between attempts. As indicated before, you can instrument the mmwavelink unit test to measure these timings:

    You can find the mmwavelink unit test under C:\ti\mmwave_sdk_03_01_01_02\packages\ti\control\mmwavelink\test\xwr68xx

    Thanks
    -Nitin