Hi
We are using Colibri iMX7d 1GB emmc V1.1A with Linux V2.8b from yocto and Colibri Evaluation board V3.2B.
We are designing our own carrier board by referring to the ‘Colibri Evaluation Board V3.2A Schematics’ pdf.
The USB OTG connector (X30A) pin 4 is USB_ID. It is connected to the SODIMM135 via a jumper JP2. What is the purpose of the pin? Is it like the normal gpio pin to enable the OTG? Whether can we use any other pin instead of 135?
Thank You for your time.
Dear, goofy,
USB 2.0 OTG
The Colibri standard does not support the full USB OTG function. However, it is possible to implement a circuit on the carrier board that allows changing the role from host to client depending on the level of the ID pin of a Micro-AB jack. The reference schematic differs from other USB OTG solutions since the module itself does not use directly the ID pin for detecting whether the port is supposed to be set in client or host mode. The pin is indirectly used. If no cable is plugged into the Micro-AB jack, the port is configured to host mode and the 5V power output (VCC_USB2 in the schematic below) is disabled. If a Micro-B is plugged in (ID pin is floating on such plugs), the VCC_USB2 comes from the cable since the system gets plugged into a host. With the help of the voltage divider, the USB_C_DET signal gets around 3.3V. This signalizes the module that it has been connected to a host and needs to switch to client mode. If a Micro-A connector is inserted, the ID pin gets shorted to ground. This ID pin enables the output of the TPS2042 power switch. This voltage on the VCC_USB2 rail is used to power any client device that is connected to the port. Additionally, the ID pin keeps over a diode the USB_C_DET signal low, even though the VCC_USB2 rail went up to 5V. This makes sure the module remains in host mode in order to be able to communicate with the client device that is plugged in.
I would leave the dedicated pin.
Best Regards,
Matthias
