search

Wren6991 / PicoDVI

Bitbanged DVI on the RP2040 Microcontroller
BSD 3-Clause "New" or "Revised" License
1.26k stars 140 forks source link

How to run 640x480 60hz with overclocking upto 416Mhz? #56

Closed xrip closed 7 months ago

xrip commented 9 months ago

I have ported bunch of emulators like NES/Genesis/GameBoy/Sega Master system to RP2040 and all of them uses VGA output. Now im hacking them to add HDMI(DVI) output aswell.

But all of them uses Pi Pico with maximum overclocking > 366Mhz (Pico XT runs at 416Mhz).

It's possible to have pico clocked at 416Mhz and have 640x480 60Hz HDMI output? setting sm_config_clckdiv seems not work or i'm doing something wrong.

Wren6991 commented 7 months ago

No, you need to serialise at exactly the TMDS bit clock, which means the system clock must be an integer multiple of the TMDS bit clock.

In practice this means the TMDS bit clock must be equal to the system clock, because twice the minimum TMDS bit clock is 0.5 GHz, faster than RP2040 will run.

xrip commented 7 months ago

I've solved this with custom, not yours, HDMI driver. It's running with clkdiv 1.5 at 378Mhz if you intersted you can take a look at https://github.com/xrip/pico-megadrive/blob/main/drivers/hdmi/hdmi.c