USB-C source input support?

[tsarath]

Hi,

System is a Mac mini 2018 with macOS Mohavi (10.14.6) connected to a Dell U3818DW (M3B106 Firmware) via DisplayPort input (USB-C/TB3 to DP adapter).

I've compiled ddcctl on my Mac mini and am able to successfully switch between DisplayPort and HDMI 1 / 2 inputs with source selection 15, 17, 18 etc. However, I'm unable to switch to the USB-C input on the Dell monitor to which I also have a separate MacBook Pro connected via USB-C as there is no input source type listed in the table.

Here are the Dell U3818DW input types supported:

Dell U3818DW Input / ddcctl source input
USB Type-C / ???
DP / 15
HDMI 1 / 17
HDMI 2 / 18

I've tried pretty much all the input options as well with no luck. Other ddcctl functions like contrast/brightness al seems to work via the DP inputs as well on the U3818DW.

Is USB-C source input type switching not supported?

Thanks.

[tsarath]

I guess it's the same issue as mentioned here (issue #67) which seems to indicate it's not supported. Happy to help contribute to get this issue resolved. Will look through the code when I get some time.

[hdansou]

I have been able to change the input source to USB-C on my Dell U3818DW with ddcctl -d 1 -i 27, which returned the following output

➜ ddcctl -d 1 -i 27
D: NSScreen #724044883 (3840x1600 0°) 111.00 DPI
I: found 1 external display
I: polling display 1's EDID
I: got edid.serial: MonitorSerialNumber
I: got edid.name: DELL U3818DW
I: got edid.name: êþ�
I: got edid.serial: êþ�
D: action: i: 27
D: setting VCP control #96 => 27

When switching back to DP, it returns

➜ ddcctl -d 1 -i 15
D: NSScreen #724044883 (3840x1600 0°) 111.00 DPI
I: found 1 external display
I: polling display 1's EDID
I: got edid.serial: MonitorSerialNumber
I: got edid.name: DELL U3818DW
D: action: i: 15
D: setting VCP control #96 => 15

[lgo]

I've found it definitely takes experimentation and I imagine the issue is likely specific to the monitor's firmware. For example, my specific USB-C monitor reports it supports DP1, DP2, HDMI1, HDMI2 capabilities even though it only has 1xDP, 2xHDMI, 1xUSB-C. Instead, its implementation appears to consider the physical DP as DP2 and USB-C as DP1 when using DDC/CI.

[greensouth]

Same here with an LG 4k 32" monitor connected to a Mac mini via USB-C (2 x HDMI, 1 x display port, 1 x USB C)

D: NSScreen #459108708 (2560x1440 0°) HiDPI I: found 1 external display I: polling display 1's EDID I: got edid.name: LG HDR 4K D: action: i: ? D: querying VCP control: #96 =? E: No data after 10 tries! E: DDC send command failed! E: VCP control #96 (0x60) = current: 0, max: 0

[hauleth]

@lgo that is because USB-C is using DP "behind the scenes" just with different connector. From the viewpoint of the device it is "regular Display Port".