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Thread: Does the Teensy 3.6 support multiple USB ports and/or software RS232?

  1. #1

    Does the Teensy 3.6 support multiple USB ports and/or software RS232?

    According to the specifications, the Teensy 3.6 has 2x USB. There is already one Micro-USB socket on the board but could I add a second socket?

    I'd like to connect the Teensy 3.6 to two different PCs and emulate USB HID keyboards on each of them. Is this possible?

    Also, is it possible to "bit bang" RS232 using the I/O ports on the Teensy or do I need a separate TTL-to-RS232 circuit?

  2. #2
    Senior Member+ Frank B's Avatar
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    USB: No this is not possible at the moment.
    Serial: How many do you need ? The 3.6 already has some in hardware. But SoftwareSerial works, too.
    Last edited by Frank B; 02-21-2017 at 07:15 PM.

  3. #3
    Senior Member+ Theremingenieur's Avatar
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    There are two sources of information: 1) The search function of this forum which would have pointed you to the information that the support for the 2nd USB port of the Teensy 3.6 is currently still under development and will in a first step give mainly USB host functionality, and perhaps later only, device functiononality.
    2) The data sheet of the MK66 processor (or a quick look into the Teensyduino Core code) would have told you that the Teensy 3.6 has 5 hardware UARTs integrated, so that slow bit banging is never needed. As soon as you code for example Serial2.begin(baudrate), the Teensy core will automatically "take away" the classic I/O functionality from the 2 corresponding pins and switch these into UART mode.

  4. #4
    Senior Member+ defragster's Avatar
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    The latest kickStarter update addressed T_3.6 2nd USB port :: https://www.kickstarter.com/projects.../posts/1811465

    T_3.6 has 6 hardware serial if you can get to the bottom pads. In any case RS-232 needs a converter as the voltage levels are not Teensy TTL compatible.

  5. #5
    Senior Member PaulStoffregen's Avatar
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    This is one of those questions that depends on the meaning of the word "possible".

    Recently I've made quite a lot of progress on the USB host software for the 2nd port. The hardware does also support device mode, according to Freescale's documentation, so in theory this should be "possible".

    In practice, programming for the powerful by complex EHCI controller is very hard. I had a tough time getting it to work (a few months of solid work so far), and I have many years of experience with USB, including previously developing multiple USB device stacks from scratch.

    On RS-232 signals, do not connect them directly to Teensy. RS-232 typically uses signal between +12V to -12V, and the spec allows even higher (though more than 12V is rare in practical use). Anything above 3.3V or below 0V can damage your Teensy 3.6.

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