Having trouble finding connected USB MIDI device

Hi JUCE Android folks,

Need some help. I’m not an experienced Android developer. I’m trying to develop a simple Android audio app that runs on a customized Android tablet and a customized usb midi input device.

I’m having trouble using juce::MidiInput::getAvailableDevices method to find this particular usb midi input device connecting to the tablet. I’ve read a couple of posts here mentioning the timing issue. So my program has a timer mechanism to give enough time for reading. But it failed. I also tried the official MidiDemo project. It failed on my hardware setup too. My current app and MidiDemo do work well on other mainstream Android tablets with USB OTG connection to the customized usb midi input device.

Where should I start finding the possible erroneous process? Is it the tablet or the usb midi input? Am I lacking some driver support somewhere?

Thanks!