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Teletext clock speed: how to send bits in 6.9375MHz speed? #29

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hasaranga opened this issue Nov 5, 2020 · 5 comments
Open

Teletext clock speed: how to send bits in 6.9375MHz speed? #29

hasaranga opened this issue Nov 5, 2020 · 5 comments

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@hasaranga
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How rpi sends teletext data in 6.9375MHz speed (fractional)?

@ali1234
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ali1234 commented Nov 5, 2020

With DISPMANX hardware scaler.

@hasaranga
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I'm trying to generate a teletext signal from fpga. The issue is generating data at 6.9375MHz speed. Is it essential to have exact data rate or can I use a rate like 7MHz?

@ali1234
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ali1234 commented Nov 6, 2020

You must have exact data rate.

@ZXByteman
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Data rate is H-sync multiply by 444. So if you have H-sync = 15625 Hz in your design, you may produce exact bit clock too.

@hasaranga
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Thanks for the idea. I will try that with a PLL.

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