TDA3XEVM: Frame Number (counter) from IssCapture

Hi Khai,

The current capture link does not support frame counter/number. You could add in in the system frame, populate in the capture link and copy it every link in you chain from input to output system buffer.

Rgds,

Brijesh

Hi Brijesh,

Thanks for the tips on adding the frame counter. I was able to add the frame counter and it replicates down to lower links and eventually out to Ethernet when external Host request the RDM data. I added this frame counter to the RDM metadata on a per frame basis.

Reason I was interested in adding the frame counter was that I observed that the RDM frames received over Ethernet on the Host were out of order. Therefore, I had to confirm that was the case by adding a frame counter. Adding the frame counter led to some very interesting discovery that I would have known if I didn't do this exercise. I seriously need to be on a call with you guys to help me understand how IssCapture really works. Somehow I got 6 chirp ADC frames for every frame counter incremented on the per framePeriodicity defined for the chirp frame. I need someone of Piyali expertise to be on a call to help walk me thru understanding of the capture framework.

Thanks,

--Khai

Here is the data that show the FFT Link processed and output old frames thus frames received over Ethernet on the Host PC is back in time:

How did you pass the frame counter info from IPU to DSP?

It looks like maybe cache coherence was not maintained properly.

HI Stanley,

I can share code that I have if we can schedule a Conf Call.

How then can I configure/set for cache coherency?

Thanks,

--Khai

You can call Cache_wb() to do cache writeback on IPU side after updating the buffer.

Then on DSP side, before reading the buffer, you call Cache_inv() to invalidate the cache.

You can search for example in SDK.

Hi Stanley,

Your suggestion fixed the out of order frame counter and angle data arrived at PC Host. Although it fixed the problem seen, it seems to slow down the throughput even more. 

I would like to understand what these 2 calls are doing. My questions:

1. Why does it go out of order without these two calls?

2. These two calls seem to somehow synchronize the frame flow with a penalty of slowing down the throughput

Thanks,

--Khai

Khai,

1. IPU and DSP both use cache inside its respective subsystem for DDR memory. If IPU doesn't call writeback, the data could still be in cache write buffer instead of DDR until some other writes push the data to DDR. When DSP reads the buffer in DDR, since it was updated by IPU, it would read from its cache first unless doing cache invalidate operation first.

2. Cache operation takes cycles. In addition, DSP will fetch the data from DDR instead of cache. For large data buffer, we typically use DMA to move data from DDR to internal memory to eliminate the overhead. For very small buffer, like a counter, you can try to use uncached memory.

"Uncached memory"? How do I specify a data structure to be allocated in uncached memory that can be written to from IPU and read from DSP?

Thanks,

--Khai

Please call Utils_memAlloc() with Heap ID = UTILS_HEAPID_DDR_NON_CACHED_SR0 to allocate memory from non cached region.

Hi Stanley,

BTW, using the Utils_mem() call to allocated uncached memory didn't work. After bootup, there wasn't any activity for a while and then I got continue error printing MBX something something error.

Do you have any idea?

Thanks,

--Khai

Sorry, just didn't recall the exact API name. That was what I used but got error

Hi Stanley,

I did use this API call to allocated metadata buffers in IssCapture create function and write the angle data to it in the process function. The board booted up but no activity for a while and then printed out MBX something something error. I am not sure why it happened so didn't work.

Thanks,

--Khai

FYI, I removed all calls to CacheWB in issCapture and Cache Invert in DSP FFT Code

It's possible there is no free memory for that section.

Please following the instruction provided under 6.3 in the below document to add a new memory section in non-cached memory region.

~/vision_sdk/docs/FeatureSpecificUserGuides/VisionSDK_UserGuide_MemoryMap.pdf

Then you can assign your data object to this new memory section.