Electronics > Projects, Designs, and Technical Stuff
Need to build On-screen display for VGA
Berni:
If you have the HDMI clock available then you simply run that into the MCU and PLL it up inside to the correct speed to run your peripherals. If not then you can still use a external phase detector to phase lock yourself to the Hsync line on VGA. The higher resolution just means you need more careful timing and you can definitely get cycle accurate timing and 100MHz SPI ports fed by DMA on todays ARM Cortex chips.
Good hardware aware programmers can squeeze amazing impossible seaming functionality from hardware. In the same way you can bitbang USB or Ethernet out of a IO pin. Just because most programmers live in a abstracted high level object oriented world doesn't mean all do, some still are in touch with the hardware.
But yeah if a full resolution detailed overlay is needed on 1080p the FPGA is the proper way to do it.
Yansi:
An then solve the issue of the PLL running with no HDMI video input etc, etc. Hack over hack, complication over complication.
Why not just doing it right from the beginning? There really are available FPGAs for as low as $5. A high performance ARM MCU like you suggested will cost multiple times this figure.
Also, do you have any specific tip on ICs to ser/des the TMDS video data? (Just asking). Dedicated RGB (DPI) to TMDS and back chips are quite rare, often expensive and under NDA (due to the HDMI money suckers).
Berni:
On a lot of modern MCUs you can run a collection of peripherals from a separate clock than the CPU and the rest and even offers automatic switchover if the clock fails. Some sort of MCU is likely needed in the design anyway and if a fairly crude OSD is needed it could do it.
It all depends on the scenario and requirements. For this case the OP has stated high resolution high quality OSD so the FPGA is the more sensible solution anyway.
Lattice Semiconductor makes a lot of video conversion chips along with there well known cheap FPGAs. They make HDMI chips capable of 4K with some signal processing or scaling and some can even work with encrypted HDCP streams. People like Texas or Analog also make HDMI converter chips.
Yansi:
--- Quote ---Lattice Semiconductor makes a lot of video conversion chips along with there well known cheap FPGAs. They make HDMI chips capable of 4K with some signal processing or scaling and some can even work with encrypted HDCP streams. People like Texas or Analog also make HDMI converter chips.
--- End quote ---
So you do not have any specific tips? I can also name all major vendors making chips. ;)
I just want a specific example of a chip (or two), that could be used here to de-serialize and serialize back the TMDS video data. Plus what the cost of such chip is.
Berni:
Its the job of the engineer designing the product to choose the chip:
https://www.latticesemi.com/Solutions/Solutions/SolutionsDetails01/HDMIInterfaceBridging
https://www.analog.com/en/products/adv7611.html
http://www.ti.com/product/TFP401A
... etc
If you do need my engineering services i do sometimes do it freelance for a fee.
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