I'm trying to use the Mini USB Host shield with the USB Host Shield 2.0 library running on an Arduino Pro Micro 3.3V.
arduino pro micro: https://www.tinytronics.nl/shop/nl/arduino/main-boards/pro-micro-3.3v-8mhz
USB Host shield 2.0 ADK examples: https://github.com/felis/USB_Host_Shield_2.0/tree/master/examples/adk
I modified the Mini USB Host shield board, I cut the trace for the VBUS, so I can power USB devices that need more than 3V3 from the RAW pin on the arduino, Later some more about this.
To test if the Mini Usb host shield works I succesfully ran the board_qc.ino sketch with comes with the USB Host shield 2.0 library.
I than succesfully ran a ADK sketch on the arduino in combination with the Mini USB Host shield & a android device. Meaning that an app on the phone started when I plugged in a usb cable from the android phone into the the microB connector on the arduino. And I confirmed through serial that communication is possible through the ADK interface.
BUT. It only works when I power the arduino with an USB cable. if I connect an external power supply to RAW on the arduino, the phone is not detected, and the app is not started on the phone, the phone is not charged either.
The external power supply is a bench lab power supply with which I supply 5V to raw.
When I use my multimeter I do see 4.97V on the VBUS pin of the USB A connector of the shield, and I see 3.315V on the VCC pins of the arduino when I use the external power supply.
I don't get it. Both usb uvcc from the microB usb connector and the RAW go to the same voltage regulator on the arduino. Why the different behaviour? And how can I get the thing working with a external power supply?
TL;DR; When using a mini usb host shield with a max3421E chip, and an arduino pro micro, I can get ADK functionality working on my Android phone. But only if I feed power to the arduino through the MicroB usb port. If I connect the arduino RAW to an external power supply the ADK functionality does not work on the Android phone.