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Re: Project: HDMI/DVI out for STFM

Posted: Sat Sep 01, 2018 8:31 am
by exxos
troed wrote:
Sat Sep 01, 2018 8:27 am
edit: Btw, did you add _both_ 100R and the cap to clk_out or just the cap?
I've not added the resistor as would have to cut a track, and didn't want to risk "slipping" and trashing the board when I only just had it :)

32MHz.. I was just thinking of removing the osc and feeding it that way ?

Re: Project: HDMI/DVI out for STFM

Posted: Sat Sep 01, 2018 8:39 am
by troed
exxos wrote:
Sat Sep 01, 2018 8:31 am
32MHz.. I was just thinking of removing the osc and feeding it that way ?
Might work ("5V" vs 3.3V but the MB 32MHz is already weird so maybe it works). My version uses one of the external pins into the 5V->3.3V buffers and from there a patch wire to the FPGA clk_in. But that's of course because I have a "proper" 5V clock from the GAL as source.

Re: Project: HDMI/DVI out for STFM

Posted: Sat Sep 01, 2018 8:41 am
by Smonson
exxos wrote:
Sat Sep 01, 2018 8:11 am
So aside from the crappy 32MHz gen on the ST, would your board work fine with the MB 32MHz if it was cleaned up ?
Yup, it only requires a 3.3v clock supplied on pin 17 (and the oscillator on the FPGA board disconnected). Alternatively you could supply the clock to pin 88 of the FPGA board and I'll create another version of the firmware that ignores the existing oscillator input.

The 5 spare pins in the vsync connector pass through a 5-to-3.3v buffer which then go on to the FPGA board. E.g. the centre pin beside vsync goes to FPGA pin 21, which can be bridged across to 17 or wherever. Troed did it this way.

Re: Project: HDMI/DVI out for STFM

Posted: Sat Sep 01, 2018 8:45 am
by exxos
Smonson wrote:
Sat Sep 01, 2018 8:41 am
The 5 spare pins in the vsync connector pass through a 5-to-3.3v buffer which then go on to the FPGA board. E.g. the centre pin beside vsync goes to FPGA pin 21, which can be bridged across to 17 or wherever. Troed did it this way.
Ah, would make life easier if theres a 5>3.3 translate already to the FPGA which I can simply wire into..

Will try and do that monday..

Re: Project: HDMI/DVI out for STFM

Posted: Sat Sep 01, 2018 8:52 am
by Smonson
I can't guarantee that the buffer will be fast enough for the 32MHz clock though, I recommend checking it on a scope before depending on it.

Re: Project: HDMI/DVI out for STFM

Posted: Sat Sep 01, 2018 10:34 am
by exxos
Smonson wrote:
Sat Sep 01, 2018 8:52 am
I can't guarantee that the buffer will be fast enough for the 32MHz clock though, I recommend checking it on a scope before depending on it.
OK, what chip did you use ?

Re: Project: HDMI/DVI out for STFM

Posted: Sat Sep 01, 2018 10:52 am
by Smonson
exxos wrote:
Sat Sep 01, 2018 10:34 am
OK, what chip did you use ?
74LVC245A
https://assets.nexperia.com/documents/d ... CH245A.pdf

Re: Project: HDMI/DVI out for STFM

Posted: Sun Sep 02, 2018 3:41 pm
by poobah
Smonson wrote:
Sat Sep 01, 2018 10:52 am
exxos wrote:
Sat Sep 01, 2018 10:34 am
OK, what chip did you use ?
74LVC245A
https://assets.nexperia.com/documents/d ... CH245A.pdf
Have you guys looked at the IDT QuickSwitch devices?

Re: Project: HDMI/DVI out for STFM

Posted: Sun Sep 02, 2018 4:20 pm
by exxos
poobah wrote:
Sun Sep 02, 2018 3:41 pm
Have you guys looked at the IDT QuickSwitch devices?
I'm using them :)

Re: Project: HDMI/DVI out for STFM

Posted: Sun Sep 02, 2018 4:37 pm
by troed
Smonson wrote:
Sat Sep 01, 2018 10:52 am
exxos wrote:
Sat Sep 01, 2018 10:34 am
OK, what chip did you use ?
74LVC245A
https://assets.nexperia.com/documents/d ... CH245A.pdf
Seems plenty fast according to that spec sheet, unless I'm misunderstanding something.