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Thread: Using the Teensy to talk to many hosts devices.

  1. #1

    Using the Teensy to talk to many hosts devices.

    Ok, it's my first time posting here, and I'm stuck at an impasse and I'm not sure how to solve it.

    What I'm try to do is use my Teensy 3.2 as a keyboard to send key commands to multiple different phones which are acting as hosts over usb.
    The reason I'm doing this is that we refurbish phones and when we flash the software on the phones our techs have to go through a lengthy startup process to get to the home screen.
    I've already figured out that you can use a keyboard at this process (I think because the phone acts as a host, and the usb keyboard as a slave) to skip this process.
    I programmed up my Teensy with the list of commands to send and it works if it is only connected to one phone.
    My next step is to hook up the Teensy to a hub or splitter and send those commands to multiple different phones all at the same time.

    This might not be a question specifically about the Teensy but more about USB architecture. Essentially what I'm trying to do is to send multiple keyboard commands (as a single slave device) to multiple different host devices.

  2. #2
    Senior Member PaulStoffregen's Avatar
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    You're going to need 1 Teensy per phone. You could use ordinary serial, perhaps with RS485 transceivers if the wires are long, to broadcast a message or instruction to every Teensy. I2C (the SDA & SCL) pins might works too, where each Teensy talking to a phone listens in I2C slave mode.

    For the USB part, the way USB works requires a separate USB device for each USB host. It doesn't work like much simpler protocols where you can use muxes or buffers to transmit from 1 device to many hosts. To make this project work, you're going to need 1 Teensy to talk to each USB host.

  3. #3
    Thanks for your insight!

    That was what I was dreading, that I would need one Teensy per phone, we already had the hubs and I was trying to find a way to save us some hardware purchasing since we already had hubs here.
    The good news is that my solution is more of a plug it in and forget about it till it does the things it needs to do.

    Thanks!

  4. #4
    Senior Member oddson's Avatar
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    Yeah but you can buy quite a few Teensy LC for what a few hours of salary cost.

    What about a MUX based thing that switches data lines to different physical USB A connectors. If when not active the powers is cut (and maybe the inputs put into a high-impedance state); would (could?) the device not connect itself when the power is restored?

    Then the device could (slowly) cycle between them with sufficient time to find the device before it sends the magic keyboard sequence?

  5. #5
    I was hoping to use the one Teensy for several phones at once, instead of one at a time. We get a large volume of phones in (about 1000 or so each day), and being able to do several at once would be good.

    It seems it is more likely we are going to get several Teensy boards per station.

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