Parallelisation of Circular Buffer Process

[aidanjohnson]

• [ ] Achieve simultaneous and continuous multi-channel recording by:
  • [ ] Using the asynchronous I/O capabilities of the board permitted by DMA. See dt78xx_aio.c (.h) here. Refer to lines 409 and 413 of main.c for web-server.
  • [ ] Implementing double (ping-pong) buffer for asynchronous input and file output stream. Ensure the file writing latency is less than the time it takes to fill a single p(i/o)ng buffer. Refer to the following links (@aidanjohnson is working on this currently)
    • [ ] Having no sample drop out (in particular between buffer changes following writing a full buffer to file). Refer to these links in AIO for background: IBM and Google. The best resource is perhaps https://oxnz.github.io/2016/10/13/linux-aio/.

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The board comes with an AIO API made by manufacturer. For the current commit that's attempting to accomplish these requirements, see commit https://github.com/aidanjohnson/dt7816/commit/919c5520de2531e883b6454648940693b673b4aa, and earlier commits on the development branch. Progress will be committed there.

Helpful links on:

AIO

• https://www.fsl.cs.sunysb.edu/~vass/linux-aio.txt
• Linux AIO documentation: http://man7.org/linux/man-pages/man2/io_submit.2.html and http://man7.org/linux/man-pages/man2/io_getevents.2.html.
• B. O. Gallmeister's POSIX.4 Programmers Guide: Programming for the Real World: see pp. 224-244 for excellent coverage on AIO
• Refer to common's dt78xx_aio.h
• Example programs: web-server (in particular main.c and in-stream.c), aio-in, and fir-filter

Double Buffering

• http://www.montefiore.ulg.ac.be/~josmalskyj/files/edma_tutorial.pdf
• http://my.fit.edu/~vkepuska/ece3552/TI%20DSP-BIOS/BIOS/Integration%20Workshop/student%20guide/iw6m08%20double%20buffer.pdf
• https://www.embedded.com/print/4017537
• https://software.intel.com/en-us/blogs/2013/12/31/bubble-bubble-toil-and-trouble-mutex-lock-and-buffer-double

[leewujung]

Do we still need to reduce the lag time if we use multi-threaded processes?

[aidanjohnson]

UPDATE 2018-09-04 21h00: Refer to commits https://github.com/aidanjohnson/dt7816/commit/c20a615fc2af7a4e519703ccd5cc3328f7717761 and https://github.com/aidanjohnson/dt7816/commit/3ba8ea4fc742f177fc575e00935ab7344068d6cd for details on the current progress of addressing this issue.

UPDATE 2018-09-26 00h30: Now refer to https://github.com/aidanjohnson/dt7816/commit/919c5520de2531e883b6454648940693b673b4aa for current status.