Author Topic: Need to build On-screen display for VGA  (Read 5419 times)

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Offline Berni

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Re: Need to build On-screen display for VGA
« Reply #25 on: February 07, 2019, 06:32:35 am »
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.
 

Offline Yansi

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Re: Need to build On-screen display for VGA
« Reply #26 on: February 07, 2019, 06:38:20 am »
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).
 

Offline Berni

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Re: Need to build On-screen display for VGA
« Reply #27 on: February 07, 2019, 06:52:16 am »
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.
 

Offline Yansi

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Re: Need to build On-screen display for VGA
« Reply #28 on: February 07, 2019, 07:09:03 am »
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.

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.
 

Offline Berni

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Re: Need to build On-screen display for VGA
« Reply #29 on: February 07, 2019, 08:00:42 am »
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.
 

Offline Yansi

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Re: Need to build On-screen display for VGA
« Reply #30 on: February 07, 2019, 01:17:56 pm »
Keep your cheeky comments for yourself. Nobody asked for them and nobody forces you to help on this forum for free, if you think you have better jobs to do.

I have just asked for specific part numbers to help isso with his project. Do you see anything wrong with that?

//EDIT: ADV7611 is an example of a "closed under NDA and paywall" type of part.
« Last Edit: February 07, 2019, 01:20:25 pm by Yansi »
 

Offline issoTopic starter

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Re: Need to build On-screen display for VGA
« Reply #31 on: February 07, 2019, 01:31:20 pm »
Wow, this thread's been quite busy  :-+  Thanks for all the useful info, I'm doing more research based on your input now.
After I'm done with OSD for VGA, my next task will be OSD for HDMI, so all of the related information that's been posted here is appreciated.

@NiHaoMike - you mentioned there were HDMI ASICs with overlay support, I'd really appreciate some part numbers if you have any. Thanks!
 

Online NiHaoMike

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Re: Need to build On-screen display for VGA
« Reply #32 on: February 07, 2019, 02:09:56 pm »
@NiHaoMike - you mentioned there were HDMI ASICs with overlay support, I'd really appreciate some part numbers if you have any. Thanks!
sil9687 is commonly found in PIP splitters and is one I really would like to find the register map for in order to be able to hack that sort of splitter for PC control using an Arduino.
Cryptocurrency has taught me to love math and at the same time be baffled by it.

Cryptocurrency lesson 0: Altcoins and Bitcoin are not the same thing.
 

Offline Berni

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Re: Need to build On-screen display for VGA
« Reply #33 on: February 07, 2019, 03:52:18 pm »
Sorry didn't mean to sound rude. Just that when you have the manufacturer you can quite quickly find a list of chips for the job on there website and choose what suits the job the best.

We used one of the HDMI receiver chips from TI and its not really that much of a hassle. Datasheets are available, chips are easy to buy from the big component vendors. But yeah the chips are not the cheapest out there and they have a rather high power consumption. For some reason i noticed the high power consumption being a common trend with HDMI chips, there is not sll that much processing going on in there do i don't see why that is the case.

In the case of confidential documentation its often not that hard to get it if you just ask them for it. As long as you look like you are a company its fine.

Sometimes getting the documentation just involves digging the internet really deep. There have been cases where i pieced together a LCD controller datasheet from datasheets of multiple other similar displays, or found a linux driver for a undocumented controller chip and reverse engineered the info out of the linux kernel driver source code for it. Also for example to get MIPI video output working on a Raspberri Pi i reverse engineered the display detection by connecting a real display and probing what its doing.

So lack of easily available documentation is not always a showstopper, but it does sometimes mean a good deal of extra work.
« Last Edit: February 07, 2019, 03:53:51 pm by Berni »
 

Offline Yansi

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Re: Need to build On-screen display for VGA
« Reply #34 on: February 07, 2019, 11:50:40 pm »
Hence why I have asked for an IC recommendation, so one could avoid such digging, as probably some of us may have experience with some ICs, that have good stock (and documentation) availability.


 

Offline Dicko101

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Re: Need to build On-screen display for VGA
« Reply #35 on: May 14, 2019, 02:34:18 am »
I need a similar solution although this all seems out of my depth now. I want to show Credits remaining and a timer over an arcade game in my store over VGA for PC or some other way for Playstation, I thought it would be simple but apparently not.
« Last Edit: May 14, 2019, 02:37:40 am by Dicko101 »
 

Offline Dicko101

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Re: Need to build On-screen display for VGA
« Reply #36 on: May 14, 2019, 03:12:01 am »
Would it be possible to manipulate just the red channel of a VGA source to do very basic red text?
 

Offline Berni

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Re: Need to build On-screen display for VGA
« Reply #37 on: May 14, 2019, 05:12:39 am »
Yep you can inject only into the red channel, the other colors will simply 'ghost' trough it, so if you do it on a cyan background the text ends up white instead.

But injecting the signal in is usually the easy part, the harder part is extracting the timing information from the existing video signal and syncing your overlay signal to it.

Tho on a PC you can probably do what you want all in software.
 


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