On Tue, Jan 19, 2021 at 7:16 PM Matt Parnell <[email protected]> wrote: > > I've been working for some time on trying to achieve the highest resolution > possible for a BeagleBone Black system I'm setting up as a dashboard running > Chronograf. > > I've tried multiple operating systems and builds (including a brief stint > with FreeBSD), but what I'm using now is a Debian 10.7 console build > (4.19.94-ti-r57) downloaded from Robert Nelson's server > (BBB-blank-debian-10.7-console-armhf-2021-01-11-1gb.img.xz). FWIW, none of > the versions I've tried (including those with LXQT) seem to make much > difference with regard to the issue I'm facing... > > The BBB seems to really want to default to 1280x1024x60. I can't get the > resolution I want - which is 1680x1050 (I really want 1920x1080, but I > suspect my monitor won't support 24 or 30 Hz). > > I've been able to get 1440x900x60 by adding "video=HDMI-A-1:1440x900@60e" to > "cmdline" in uEnv.txt. Unfortunately, setting this to 1680x1050x60e seems to > cause the resolution to revert to 1280x1024. BTW - what does the "e" suffix > do? I've tried with and without, and haven't figured out what its > significance is. > > I don't see 1680x1050 in the list on > https://elinux.org/Beagleboard:BeagleBoneBlack_HDMI#Supported_Resolutions, > but from I've read it should work? > > I read somewhere that resolutions/bandwidth are limited via the audio > channel. So I've also tried disabling HDMI audio (I don't use it) by > un-commenting "disable_uboot_overlay_audio=1". > > My monitor, by the way, is an older HP Compaq LA2405x. I have confirmed that > it supports 1680x1050 at 60 Hz. It is connected to the BBB via a mini HDMI > to HDMI cable, then an HDMI to DVI cable. I'm nearly certain that the > monitor isn't the issue, as it will report on-screen if an input > resolution/frequency is out of range (and I'm not getting that). > > I've also tried setting the resolution for my Xorg session, but from what I > can tell, the driver (fbdev?) doesn't permit changing resolution. When I run > xrandr, it seems to indicate that my minimum and maximum resolution is equal > to the resolution I've already forced via uEnv.txt. > > Forgive me if I've missed important details or this is a bit scattered. Most > of this effort occurred over the weekend (before I had access to this group), > so I'm trying to re-visit the key steps I took (ignoring many that appeared > to have no impact).
I don't remember where this is explained in the u-boot/kernel code. But the BeagleBone Black's AM335x just doesn't have enough memory bandwidth to fully support "large" screen sizes.. This is why 1080p maxes out at 30 fps, or 24 fps when audio is also involved.. The 'e' is documented here: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/fb/modedb.rst?h=v5.11-rc4 "DRM drivers also add options to enable or disable outputs: 'e' will force the display to be enabled, i.e. it will override the detection if a display is connected. 'D' will force the display to be enabled and use digital output. This is useful for outputs that have both analog and digital signals (e.g. HDMI and DVI-I). For other outputs it behaves like 'e'. If 'd' is specified the output is disabled."... Regards, -- Robert Nelson https://rcn-ee.com/ -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/CAOCHtYjhM6WVtdBKqb_3U3X_inRqHHGk%2BaW5a4TcV5Akq9OHtg%40mail.gmail.com.
