USB exploration: USB sound, keyboard, mice, storage together

What hardware have you tested to connect and power through the PPM? Have you noticed any interesting side effects?

The PPM worked OK with:

  • a simple USB sound card, that could both record and play audio through the connected headset,
  • three non-powered hubs daisy-chained (the final one of which is ancient, pre-USB 2.0),
  • multiple storage media connected via USB stick and card reader,
  • multiple mice (all control the same pointer as the airmote),
  • and a physical keyboard.

Some slight issues with the above that could be improved:

  • I can’t find how to switch to Nordic/Swedish keyboard layout for the physical USB keyboard.
  • When I open the file manager app I am presented with a choice between Internal (the PPM:s internal flash), SD (the PPM:s own micro-SD slot) and USB (storage connected via USB). However, when selecting USB with multiple storage media connected there, the next dialog asks me to select one of them based on its volume serial number, not the volume label.

These did not work for me:

  • I tested a basic SSD in a USB 3 enclosure (on its own, as well as attached to the USB 2.0 hub). It lit up its blue LED, and the PPM:s hidden menu showed it was recognized as storage. However, it had status “safely ejected”.
  • A Canon LiDE 210 USB-powered scanner showed no signs of life. I did not test finding Android drivers for it yet though :).


The first picture is hardcore! Seems it will be fun once I get mine.

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There’s a Dutch mobile phone provider that has as slogan: “Not because it has to, but because it can”
That’s what the first image invoked in me.


Just out of curiosity: why would you want to connect a scanner to the PPX?

If I am a teacher in a school for younger children, some of them might bring presentation diagrams on paper rather than in a powerpoint file on a USB stick. Some of the work could also be in other non-paper (but still flat) form.

  • I could connect the scanner to my own laptop, scan it, move the file to a USB stick, unplug it and move it to the projector.
  • I could take a photo with my cell phone, and cast it to the projector.
  • Or, if I could connect the scanner to the projector, they could scan it and bring it up on-screen right away (if I find an app that supports this).

Note, I am not sure whether this would be a viable workflow. The two earlier workflows have more steps, but they would be better suited for pipelining, to let one student prepare their upcoming presentation while an earlier student is showing theirs. Pipelining might cause distractions within the classroom though, stealing the attention of either me or some student(s). I want to test what is possible, before I decide if it is useful.

This is similar to the reason I wanted to test what happens when you plug in multiple mice. USB cables can be up to 5 meters, or you could use wireless mice (non-bluetooth, with their own USB-dongle). If you have multiple groups collaborating on the thing you are projecting, you would not need to pass the mouse around. I don’t know yet whether it is helpful for anything, but now that I know it is possible, I can see if it becomes relevant.