sdc.engine
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Serial Video Output, multiple TFT

Mon Nov 04, 2013 1:24 pm

Hi there,

I'm working with TFT LCD displays and I would like to use RaspberryPi as media center with several display connected at the same time.
Suppose I mount 4 displays (each one with its own graphic driver), it would be good connect these to raspberry via serial. In this case the video output should be splitted into 4 parts, one for each display, and send these all on serial bus.

Alternatively, I can put 4 video on RaspberryPi and send them at the same time on the serial bus, but how can I do that? Is it possible by writing a python script?

Can anyone help me? Thanks in advance! ;)

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Davespice
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Re: Serial Video Output, multiple TFT

Mon Nov 04, 2013 1:36 pm

You could achieve this with just a HDMI splitter device. You would connect the output of the Pi to the input of the splitter and then all your screens to the other outputs of the splitter.
http://www.amazon.co.uk/dp/B00CXVXBY6
Image
No need to do anything with the serial port.

karlkiste
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Re: Serial Video Output, multiple TFT

Mon Nov 04, 2013 3:49 pm

A good quality HDMI splitter is likely more expensive than three extra pis...

ghans
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Re: Serial Video Output, multiple TFT

Mon Nov 04, 2013 4:20 pm

I think this might be what you need:
http://www.piwall.co.uk/

ghans
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sdc.engine
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Re: Serial Video Output, multiple TFT

Tue Nov 05, 2013 1:56 pm

I can't use the hdmi switch because TFT screens haven't hdmi ;) (I'll use 480x272 display)
A very good solution is piwall
but it's not exactly what I need.
I want to use just the master rpi as they use it but a simply MCU as graphic driver for each screen e.g. something like that: http://www.forenex.com.tw/eng/product/m ... 1&topage=1 )

ghans
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Re: Serial Video Output, multiple TFT

Wed Nov 06, 2013 6:22 am

Whats the resolution and Framerate you need ?

ghans
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sdc.engine
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Joined: Mon Nov 04, 2013 11:59 am

Re: Serial Video Output, multiple TFT

Tue Nov 19, 2013 8:48 am

[quote="ghans"]Whats the resolution and Framerate you need ?

ghans[/quote]

Resolution can be both 4.3" (480*272) or 3.5" (320*480). Framerate enough for watch video, between 20 and 25 fps.

I've found this TFT [url]http://bit.ly/1fR9dBG[/url] with serial interface, but it hasn't buffer memory so I think raspberry should send video data on serial bus to every displays in real time. Do u think rpi can do that?

karlkiste
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Re: Serial Video Output, multiple TFT

Tue Nov 19, 2013 9:31 am

sdc.engine wrote:I've found this TFT http://bit.ly/1fR9dBG with serial interface, but it hasn't buffer memory
I read

"With built in controller and memory
...
No overhead on firmware/processor for refreshing"

like it does have memory. Real-time display data is usually sent via TTL, LVDS or some special sort of serial transmission. 320x480 pixels x 16 bit color x 30fps = 74MHz. Usual SPI applications go up to 10, maybe 20MHz. Perhaps some are even faster, but 74MHz is not within a usual range.

I've read that it's possible to output 100MHz on the GPIO pins of the pi, but not more. So, even if it was possible to connect SPI at such a speed, it won't suffice for more than one display.

sdc.engine
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Joined: Mon Nov 04, 2013 11:59 am

Re: Serial Video Output, multiple TFT

Tue Nov 19, 2013 3:44 pm

thanks karlkisten for answering!
info on webpage are wrong, I've been talking with the company support and they assured me that this is just a LCD with spi interface, so without memory.
due to spi velocity I could use a board with internal media player, in this way I can load video data to internal memory and then use spi just for send command for sync all players. it' may be a more expensive solution, but i don't find other one.

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