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MJoergen / C64MEGA65

Commodore 64 core for the MEGA65 based on the MiSTer FPGA C64 core
GNU General Public License v3.0
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DVI: Autodetect monitor capabilities and auto-activate DVI mode #121

Open sy2002 opened 10 months ago

sy2002 commented 10 months ago

If one has a display / monitor that does not support HDMI but only DVI, then the screen stays black when the core is started. Our current "workaround" for this situation is this recipe that users can run through:

https://github.com/MJoergen/C64MEGA65#hdmi-compatibility

Using M2M's new I2C features, we can find out the monitor's capabilities and automatically activate DVI mode for such displays.

MJoergen commented 1 week ago

Looking at the wikipedia page https://en.wikipedia.org/wiki/Extended_Display_Identification_Data it seems that byte 20, bits 3-0 can be used to differentiate between a HDMI monitor and a DVI-only monitor.

MJoergen commented 1 week ago

@sy2002 : In order to test this, it would be nice to have the model number of a specific monitor that will benefit from this fix.

MJoergen commented 1 week ago

The current version of M2M (in V5.1) supports QNICE access to the HDMI I2C EDID rom, as follows:

  1. Write 0x0005 to 0xFFF4 (access I2C controller)
  2. Write 0x0350 to 0xFFF5 (access I2C address 0x50 on HDMI)
  3. Read from 0x7114 (direct I2C memory map access to register 0x14)

This is exactly the byte number 20 mentioned in the previous comment.

MJoergen commented 1 week ago

Data point for my monitor "Philips 272S1" (which does support sound):

The DisplayPort connector on the monitor returns the value 0xa5. Bits 3-0 => DisplayPort The HDMI connector on the (same) monitor returns the value 0x80. Bits 3-0 => Undefined

sy2002 commented 1 week ago

@sy2002 : In order to test this, it would be nice to have the model number of a specific monitor that will benefit from this fix.

@MJoergen I asked the community for support. See this Discord message: https://discord.com/channels/719326990221574164/801767398675316756/1305176385836417055

paich64 commented 1 week ago

If it can help as a reference my 2 DELL monitors which are pure DVI monitors P190ST and P1913SB are working great with a HDMI to DVI cable. Never had any issue to get the correct display with both Mega65 & C64 core (whatever the C64 core release).

Piramania commented 1 week ago

Samsung 2433SW (DVI+VGA) here :)

Schwefelholz commented 1 week ago

Lenovo LT1913pA Wincor-Nixdorf PA10

Both DVI and VGA

sy2002 commented 1 week ago

Thank you @tonedef71 for this info via Discord:

I have a Sceptre 19" VGA monitor that supports DVI.

sy2002 commented 1 week ago

Thank you to Matt84 for this info via Discord:

I have a benq bl3200pt that has dual link dvi input that works at 1440p I could test with

Kiwi-Phoenix commented 1 week ago

Dell P2714H (DVI & VGA) - This one seems to work fine. Apple Cinema HD Display (DVI) - Does not work with Mega65 but is fine with Windows & Macs. Both using HDMI-DVI cable.