I have an old USB midi keyboard controller that I want to use with my modern iPad.
It has MIDI output over standard DIN connectors, as well as a USB port for connecting to Mac/PC, but it’s not ‘class compliant’ (meaning that to use it with Mac/PC you’d need to have the appropriate drivers installed on your system).
I obviously can’t install any drivers on my iPad, so as a workaround I am powering the keyboard via the USB port and then connecting the DIN port to the iPad via an old MIDI to USB converter cable I had lying around. This isn’t the most elegant solution, however, and I’d really love to get it working with just one USB cable coming out of the back and going into my iPad. I wondered, therefore, whether there was any way I could solder my MIDI to USB converter cable inside the keyboard so that the signals/data it put out through the USB port would be readable by my iPad as standard MIDI whilst also being powered via that same lead?
Should this be as straightforward as simply chopping off the end of the MIDI cable and soldering it to the back of the DIN connector inside my keyboard, and then chopping off the end of the USB cable and soldering that to the pins of the USB connector on the back of the keyboard?
Hacking USB MIDI into an old non class-compliant MIDI piano keyboard?
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- KVRist
- Topic Starter
- 47 posts since 5 Aug, 2008
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- KVRAF
- 1869 posts since 21 Feb, 2004 from somewhere! anywhere!
Hi,
There's a possibility that the combination might draw too much power. When I connect older (btw all class compliant) controllers to my iPad, that's the message I get ("The connected device uses too much power") so I have to use a powered USB hub. I'm using a fairly old iPad, however, so things may have changed in terms of how much power they can supply?
I'd be curious to know which controller you have and whether you've already tried plugging it in to the iPad via USB - if so, what message, if any, does the iPad flash up? Does it actually power up regardless of not being class compliant?
If it doesn't draw too much power then theoretically, your idea could work but probably worth testing before cutting up the converter.
Before removing the plugs at either end, I'd open up the MIDI to USB converter 'box' that houses the circuit board and look to tap the 5 volts off of that. Take an old USB cable and cut off the end that usually plugs into a PC, then solder its power wires to the 5 volts and ground on the converter's circuit board. Connect the controller to iPad via the converter as before and then plug the newly attached USB cable into the controller and confirm it powers up. If it doesn't then it's probably not worth going any further and you can easily restore the converter to it's original state.
However, if the iPad is happy with that, then you could go for your more elegant solution. There may still be some potential issues/conflicts. For example, you may need to disconnect the controller's own data lines so that only it's power lines are connected to the USB socket. That way the data lines are exclusively used by the MIDI converter.
Hope that's helpful...
There's a possibility that the combination might draw too much power. When I connect older (btw all class compliant) controllers to my iPad, that's the message I get ("The connected device uses too much power") so I have to use a powered USB hub. I'm using a fairly old iPad, however, so things may have changed in terms of how much power they can supply?
I'd be curious to know which controller you have and whether you've already tried plugging it in to the iPad via USB - if so, what message, if any, does the iPad flash up? Does it actually power up regardless of not being class compliant?
If it doesn't draw too much power then theoretically, your idea could work but probably worth testing before cutting up the converter.
Before removing the plugs at either end, I'd open up the MIDI to USB converter 'box' that houses the circuit board and look to tap the 5 volts off of that. Take an old USB cable and cut off the end that usually plugs into a PC, then solder its power wires to the 5 volts and ground on the converter's circuit board. Connect the controller to iPad via the converter as before and then plug the newly attached USB cable into the controller and confirm it powers up. If it doesn't then it's probably not worth going any further and you can easily restore the converter to it's original state.
However, if the iPad is happy with that, then you could go for your more elegant solution. There may still be some potential issues/conflicts. For example, you may need to disconnect the controller's own data lines so that only it's power lines are connected to the USB socket. That way the data lines are exclusively used by the MIDI converter.
Hope that's helpful...
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- KVRAF
- 15329 posts since 8 Mar, 2005 from Utrecht, Holland
Chances are the USB socket of the keyboard is mounted directly on the PCB. That will complicate things...
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- KVRist
- Topic Starter
- 47 posts since 5 Aug, 2008
Thanks for the info, guys.
I'm also using a powered USB hub, so after confirming that the keyboard AND iPad AND MIDI <> USB converter worked on the same usb hub power, I ripped open the keyboard (it's an M-Audio Radium 49), soldered the USB power line to the MIDI <> USB adapter board, and then just ran the cables out of a hole I made in the back of the keyboard case and plugged the MIDI into the MIDI out of the keyboard.
It's in no way elegant, but it works! I wanted to wire the keyboard's MIDI DIN out directly to the MIDI input of the converter, but after a few attempts I just couldn't work out the wiring. Ideally like you said @BertKoor I'd like to have disconnected the keyboard's USB data lines and patched it into that port, but I didn't have the necessary tools/knowledge to do that so that can be a job for a future improvement
But right now I have what I wanted - one cable out of the keyboard that both powers the keyboard, and the adapter, and transmits MIDI over USB.
I used to get that error message all the time before I ponied up and spent more money on the OFFICIAL Apple USB adapter to solve this issue. I never see that any more with the official one.
I'm also using a powered USB hub, so after confirming that the keyboard AND iPad AND MIDI <> USB converter worked on the same usb hub power, I ripped open the keyboard (it's an M-Audio Radium 49), soldered the USB power line to the MIDI <> USB adapter board, and then just ran the cables out of a hole I made in the back of the keyboard case and plugged the MIDI into the MIDI out of the keyboard.
It's in no way elegant, but it works! I wanted to wire the keyboard's MIDI DIN out directly to the MIDI input of the converter, but after a few attempts I just couldn't work out the wiring. Ideally like you said @BertKoor I'd like to have disconnected the keyboard's USB data lines and patched it into that port, but I didn't have the necessary tools/knowledge to do that so that can be a job for a future improvement
But right now I have what I wanted - one cable out of the keyboard that both powers the keyboard, and the adapter, and transmits MIDI over USB.-
- KVRAF
- 1869 posts since 21 Feb, 2004 from somewhere! anywhere!
seems you got there...
FWIW, I'm also using the official Apple USB adapter - but, as I said, it's a slightly older iPad and the power issue occurs with older, power hungry controllers.
FWIW, I'm also using the official Apple USB adapter - but, as I said, it's a slightly older iPad and the power issue occurs with older, power hungry controllers.
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- KVRist
- Topic Starter
- 47 posts since 5 Aug, 2008
Yeah I know what you mean; I just got this newer iPad but until then was using an older one (iPad 2!) and that always threw up errors 
