Cm2 Dongle Support -

It hardwires the connections without complex negotiation, so the compute module sees a simple HDMI signal and USB data lines.

Why? Because most compute module carrier boards use the USB-C port in or dual-role mode, but they don’t implement the full Alternate Mode (Alt Mode) negotiation that commercial hubs expect.

| Symptom | Likely Fix | |---------|-------------| | No HDMI, but USB works | Reboot with HDMI and power connected before boot | | No USB, but HDMI works | Dongle needs external power; don’t rely on carrier board back-power | | Flashing or corrupted display | Lower resolution in config.txt; try hdmi_mode=4 (720p) first | | Dongle gets hot | Normal for C2M dongles—they are passive and lack power regulation. Unplug when not in use | cm2 dongle support

dtoverlay=disable-bt # optional, frees up UART if needed hdmi_force_hotplug=1 hdmi_group=2 hdmi_mode=16 # 1080p 60Hz, change as needed The hdmi_force_hotplug=1 is the key—it tells the GPU to output HDMI even if no display is detected at boot.

Happy making, and may your dongle always be detected. It hardwires the connections without complex negotiation, so

Here’s why people get stuck: A standard USB-C hub (like one from Anker or Dell) works with phones and laptops. Plug it into a Raspberry Pi CM4 carrier board… and nothing happens .

Remember the golden rule: . Get the order right, and you’ll save hours of frustration. | Symptom | Likely Fix | |---------|-------------| |

At first glance, it looks like a typo for “USB-C to HDMI.” But C2M (Computer-to-Module) dongle support is something entirely different—and if you work with developer boards like the Raspberry Pi CM4 or CM5, it’s a game-changer.