Hi Sir,
In our current project, our product has only “one” “USB-C” port, running USB 2.0 High Speed. Our target application is to use this USB port as USB host role to connect USB stick or solid state drives for local recording.
However, our next revision PCB circuitry is to pull up 56K Ohm to VCC_5V0 on both CC pins of USB-C, as shown below. That is, we hardwire fixed the USB port to USB host based on CC configuration definition. There is no separate Jumper / Switch / Type-C Controller(DRP(Dual Role Port) logic IC) circuitry that can switch the CC pin between host and device.
We would like to know, based on this circuitry, can i.MX8M+ USB Serial Download Mode still work? We understand when i.MX8M+ Boot ROM activates USB Serial Download mode, the port is automatically configured as a USB device(for USB Serial Download mode to work), but that should mean the chip's ROM code only controls the internal USB PHY to be device mode, it cannot override the hardware's external CC resistor states(Type-C Port role). As a result, the PC is entirely unable to enumerate the i.MX 8M Plus via USB(both cannot finish handshaking(Type-C Attach) from USB physical layer point of view), which causes the UUU programming to fail. If the above statement is correct, the USB Serial Download Mode will become inoperable before boot(i.e. will not work at all), resulting in the loss of factory production flashing and system unbricking capabilities.
Is our understanding correct?
Best regards