Weekly Report: Week4

Only one week left to complete midterm tasks. Heartbeat is integrated with firmware and ready for merge with upstream. Documentation on 16 bit float is ready, with a need for few minor edits.

Updated just the Opsis firmware

Continuing with last week’s work on Opsis, I focussed on understanding how to upload a updated firmware without recompiling the gateware (which takes 20-30 minutes). I encountered some issues with correct FX2 USB IC modes. I will start will steps necessary to successfully load an updated firmware to opsis.

  1. Last week I had discussed how to upload gateware to opsis using make load-gateware. It is important that we have a .bit bitstream file for uploading the gateware. Next do make load-gateware, this is what we had achieved last week. Make sure that the FX2 USB IC is in correct jtag mode for this. This steps step needs to be done before we hack around with firmware code, this is because Opsis might be shipped with a previous version of gateware and current firmware might not be compatible.
    $ make load-gateware
    
  2. To test the if the firmware is correctly updated or not, I added some lines to pattern.c, in the pattern_fill_framebuffer() function. After this use HDMI2USB-mode-switch discussed last week to switch to serial mode.

    $ ./<path>/hdmi2usb-mode-switch --mode=serial
    

    Note that the make load-firmware command for uploading just firmware works only when FX2 USB IC is in serial mode. Toggle between jtag and serial mode once or twice to set the FX2 USB IC in correct serial mode.

  3. Next type make load-firmware, this will compile any updated C files and load the updated firmware. If the compilation and build steps are successful, it opens the serial terminal and we get HDMI2USB> prompt

    $ make load-firmware
  4. At the HDMI2USB prompt, type reboot. It should say something like
    Booting from serial…
    sL5DdSMmkekro
    [FLTERM] Received firmware download request from the device.

    HDMI2USB> reboot
  5. If you get [FLTERM] Got unknown reply ‘T’ from the device, aborting then there has been an error downloading via the serial port. To resolve this, we need to switch to jtag and then back to serial mode of the FX2 USB IC using the HDMI2USB-mode-switch tool. This is similar to what we did for uploading gateware which used to jtag usb mode.

    $ ./<path>/hdmi2usb-mode-switch --mode=jtag
    $ ./<path>/hdmi2usb-mode-switch --mode=serial

You should get updated pattern after this on the specified output. This means that firmware update was successful. You can also check the version information.

Adding heartbeat functionality to firmware

I have been working on adding the heartbeat functionality(#234) to the firmware for several weeks now. The C code was almost ready. Initially I was unable to load firmware with a new file for functions. This was because Makefile in firmware/lm32/ has predefined list of objects or the *.o files, which required including the heartbeat.o file manually.

Once I had figured out how how to load firmware, the first natural step was to understand how an individual pixel can be modified by making some changes in firmware. Tested this on pattern_fill_framebuffer() by making small changes to particular locations of framebuffer. Once I had figured out how to generate the required square at right bottom corner, I looked for ways to integrate it with timing functions to implement beating.

I enabled the pattern_service() function in processor_service() function to understand the timing related stuff. Once I had figured out the correct timing frequency, I added the timing code to my heartbeat function and tested it on pattern. This looked to be working fine. working video

Tested the same for hdmi_in0 as input, there were some glitches in the output of hdmi_in0, which maybe due to timing inconsistency or some kind of memory conflict. Added support for all the three possible inputs, hdmi_in0, hdmi_in1 and pattern. I added the three heartbeat functions in processor_service function. There is some glitch in output when all three run together. There might be better ways to integrate the heartbeat function. glichy video

Next, I made the required changes in ci.c files to get an option for enabling or disabling heartbeat at HDMI2USB> prompt.

Documentation of 16 bit float

The pixel data for RGB as well as YCbCr corresponds to 8 bit for each channel. Since we will be doing a number of operations on this pixel data it is important that data type gives us sufficient precision. Hence we convert the 8 bit pixel data to 16 bit float for further operations like gamma correction and linear mixing. I have documented the 16 bit float format in detail in the document link. This documents covers in detail the actual 16 bit float format, conversion and implementation of arithmetic operations.

Adding support for rgb16f to/from xxx in gateware/csc

I have already documented methods for this conversion in the design document linked in the previous section. I started with understanding the existing methods for conversion of rgb to ycbcr and other modules. This was first time I was dealing with a Migen code, so it was pretty alien to me in the first time.

The existing modules in csc are implementing the necessary conversion using pipelining, with some modules taking as much as 8 pipelined stages. The float conversion modules will follow very similar steps, and hence I started building up upon the existing modules by making changes wherever necessary. Although I had started with migen related things to learn something new and interesting, I went back to completing other things ongoing in my project.

Some of migen documentation I found online,

RLE Code: Couldn’t proceed due to lack of time this week. I will try to complete this first thing in the upcoming week.

Upcoming Week’s Task

  • Adding conversion modules for 16 bit float conversion in csc module.
  • Add migen code for multiplication
  • Cleanup of RLE codes
  • Update design documentation
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