Using Rock Pi S as MIDI Gadget - slight problem

Hi All,

I’ve just started my Rock Pi S adventure and have a little problem.

Ultimately, I want to connect it to my PC as a multi-port MIDI device translation unit - I’ve got a set of cascaded eMagic amt8/Unitor8 devices which are attached to a Windows PC. Unfortunately, eMagic was bought by Apple quite some years ago, and since this time, no new Windows MIDI drivers for their nonstandard USB implementation have been created - the last one is for Windows XP, 32-bit. My machines, unfortunately, are all 64-bit Windows 10, so … no joy, no MIDI. Replacing my whole studio infrastructure would be no fun, and would come at a high price, so why not add a little intermediary device?

Enter stage from the left: Rock Pi S!
In theory, this little fellow should allow me to set up the OTG port as a set of standard MIDI devices, with 8 input/output ports each. Then connect the amt8/Unitor8 cascade to the host port, implement a little “magic translation program” in the middle, and off we go … at least, I hope that’s how it will work.

First step: let my Windows PC see the Rock Pi S as a set of MIDI devices. To do so, I did the following:

1. Disable ADB

That was easy:

systemctl stop rockchip-adbd
systemctl disable rockchip-adbd

did the trick, as per the documentation at

2. Set up the MIDI devices

Hmmm … not as easy, but doable. Following a modified version of the method I found here, I created a file called /usr/bin/create-midi-gadgets with the following content:


# Load libcomposite
modprobe libcomposite

# Create a gadget called usb-gadgets
cd /sys/kernel/config/usb_gadget/
mkdir -p usb-gadgets
cd usb-gadgets

# Configure our gadget details
echo 0x1d6b > idVendor # Linux Foundation
echo 0x0104 > idProduct # Multifunction Composite Gadget
echo 0x0100 > bcdDevice # v1.0.0
echo 0x0200 > bcdUSB # USB2
mkdir -p strings/0x409
echo "fedcba9876543210" > strings/0x409/serialnumber
echo "Rock Pi S Gadget" > strings/0x409/manufacturer
echo "Rock Pi S Gadget" > strings/0x409/product

mkdir -p configs/c.1/strings/0x409
echo "MIDI Multi" > configs/c.1/strings/0x409/configuration
echo 250 > configs/c.1/MaxPower

# MIDI gadget 1
mkdir -p functions/midi.usb0
# id     - ID string for the USB MIDI adapter
echo "rock-midi-1" > functions/midi.usb0/id
echo "8" > functions/midi.usb0/in_ports
echo "8" > functions/midi.usb0/out_ports
ln -s functions/midi.usb0 configs/c.1/

# MIDI gadget 2
mkdir -p functions/midi.usb1
# id     - ID string for the USB MIDI adapter
echo "rock-midi-2" > functions/midi.usb1/id
echo "8" > functions/midi.usb1/in_ports
echo "8" > functions/midi.usb1/out_ports
ln -s functions/midi.usb1 configs/c.1/

# End functions
ls /sys/class/udc > UDC

(created as root, followed by chmod u+x).
Then I created a service definition for that in /etc/systemd/system/create-midi-gadgets.service :

Description=Create MIDI gadgets



and made sure the Rock Pi S boots with that:

systemctl daemon-reload
systemctl enable create-midi-gadgets

and hey … when I boot the S attached to my PC, up come two MIDI devices! Yay!
… or not so yay.


While I did configure different IDs for the MIDI devices (they should be called “rock-midi-1” and “rock-midi-2”), the IDs are obviously not used by the created gadget. Windows sees them as:

MIDI function
MIDI function

and the enumerated MIDI devices have the names

MIDI function
MIDIIN2 (MIDI function)
MIDIIN3 (MIDI function)
MIDIIN4 (MIDI function)
MIDIIN5 (MIDI function)
MIDIIN6 (MIDI function)
MIDIIN7 (MIDI function)
MIDIIN8 (MIDI function)
MIDI function
MIDIIN10 (MIDI function)
MIDIIN11 (MIDI function)
MIDIIN12 (MIDI function)
MIDIIN13 (MIDI function)
MIDIIN14 (MIDI function)
MIDIIN15 (MIDI function)
MIDIIN16 (MIDI function)

(same “logic” for the output ports).

So, 2 have the same name, which is bad.

Does anybody know what I have to correct in my little script to assure that the IDs are used?

I used rockpis_debian_buster_minimal_arm64_20200809_0853-gpt.img, in case this is relevant.

Thank you very much!

Will check this issue.

Since it’s been over a week now - any news?