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Original question:

AWR1843BOOST: What exactly is Core Local RAM (LRAM)?

AWR1843BOOST: mm-wave demo: clarification on subframes and frame

u4564981
Intellectual 445 points
Part Number: AWR1843BOOST
Other Parts Discussed in Thread: STRIKE

Hello there, 

Might be silly - I wanted some clarifications on subframes and frames. In my understanding, a frame may consist of multiple types of chirps (subframes), as in the TI Automotive Toolbox's Medium Range Radar example. However, in the demo example provided with SDK (xwr18xx), the documentation mentions four subframes, while the frame consists of a single type of chirp. So what does subframes 0 to 3 refer to here? Also, any particular reason for 4 four subframes?

Also, if it does refer to multiple types of chirps in a frame, do they occur in the format (in a single frame): subframe 0 acquisition period  -> subframe 0 processing period -> subframe 1 acquisition period -> ...  -> subframe 3 processing period? 

Thanks.

  • 0
    TI__Guru*** 148334 points

    Hi,

    Please see Section 6 "Advanced Chirp Configurations" for information about the Sub-Frame definition

    The mmWave SDK demo uses 4 sub-frames because this is the max number of subframes supported. This is just an example of the cababilities of the device

    The chirp configuration is the same. This is similar to using a standard single frame. The demo wanted to provide an example on how subframes are used.

    Thank you

    Cesar

  • 0
    TI__Guru 69960 points

    Hi,

    Above snapshot explains about processing part of ADC data based on AdvFrameConfig, let me provide basics of AdvFrameConfig here.

    The advanced frame configuration available in TI’s mmwave sensor allows for large flexibility to have multiple chirp configurations in a single frame. The frame can be constituted using a sequence of “sub-frames” with each of these sub-frames representing a different radar mode. The rlSetAdvFrameConfig API helps enable this kind of configuration.

     

    To provide maximum flexibility of the chirps within a frame the advanced frame config API provides the ability to break a frame into different sub frames (up to 4). Each of the sub frames consists of multiple bursts of chirps (up to 512 bursts). Each burst can consist of 512 unique chirps which are associated to one of the 4 profiles, and the start chirp index can be programmed to have a fixed offset from the previous burst. A set of bursts in a sub-frame can be further looped in software up to 64 times. The below figure is an example how a sub frame is formed.

    In this configuration user can configure multiple type of frames compare to legacy frame configuration where only one type of frame is permitted. Advanced frame-config allows upto four sub-frames, with multiple bursts in each sub-frame. 

    Here one burst is equivalent to one legacy frame configuration.

    Regards,

    Jitendra

  • 0
    TI__Expert 5235 points

    The timing diagram you quoted may have confused you a bit, this is a high level diagram showing the case of no advanced frame configuration, it is the baseline frame configuration. You can see a little bit better in later diagrams : one is in the "Stats Information" section and another in LVDS section named "LVDS timing diagram" which shows the sub-frame related processing (sub-frame switching) although it does not show multiple sub-frames very clearly within the full frame time as the intent was to focus on the timing part [which would just be replicated for each sub-frame and would unnecessarily extend the picture without any new information].

    In his post, Jitendra gave you the details of advanced frame configuration capability at the mmwavelink level, but in the demo, we limit its usage to a less general situation where we only allow within each sub-frame the same level of capability as you would in a baseline (not advanced) frame configuration i.e the processing is not generalized to handle anything but numOfBursts = numOfBurstLoops = 1 [which you give through the CLI command "subFrameCfg" and is illustrated in demo\xwr18xx\mmw\profiles\profile_advanced_subframe.cfg which you can give through the visualizer GUI]. In your configuration, you can configure anywhere from 1 to 4 sub-frames depending on how you want to use the feature, but because of the burst/burtloop limitation I mentioned, the sub-frame of 1 degenerates to the baseline case so the sub-frame feature is practically only relevant when you need 2 to 4 sub-frames. Give the limitation, you can think of each sub-frame as a smaller frame by itself, just that you are able to automatically switch the chirp configuration when going from one frame to another both on the RF (due to the advanced frame configuration capability in the BSS firmware and hardware) and the demo processing will automatically do the necessary switching of its own configuration at the end of one sub-frame to prepare the processing chain for the next one, so there is some switching compute overhead. The sub-frames in the demo allow you for example to strike different trade-offs of max range, max velocity, range resolution, velocity resolution among different sub-frames to get an overall desired performance that couldn't otherwise be achieved with the non-advanced (or 1 sub-frame) case.