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Thread: Teensy 3.2 board and SBUS Receiver

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    Teensy 3.2 board and SBUS Receiver

    Hi,
    I want to build a USB dongle that I can use as a receiver for my RC radio.
    I found the Teensy 3.2 board, but I have a problem: the Teensy only supplies 3.3V and 10mA. My SBUS receiver needs 5V and 30mA.
    Can I get the 5V directly from the USB port?

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    Assuming you are powering the Teensy via USB, you can get the 5v from the VIN or VUSB pins. Normally VIN and VUSB are connected, but there is a solder mask underneath the Teensy that if cut, it no longer connects VUSB to VIN, and you will need to power the Teensy with external power to VIN.

    How much power you can draw depends on your power source. There is a 500 mA fuse between VIN and VUSB that puts a cap on the amount of power. But getting 5v and 30mA should not be a problem from a normal USB connection.

    One suggestion is to put a switch on the Teensy that prevents it from doing the USB stuff. That way, you can more easily re-program the Teensy. I recall running a Teensy sketch that sent out mouse movements over USB, and it was hard to get it re-programmed without having to manually hit the program button.

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    First of all: I don't have the Teensy 3.2 until now, because I want to make sure that it works with my SBUS receiver.
    I want to power it from the USB port. On the back side I see VUSB, but not VIN.

    What kind of switch are you thinking about and where can I order it?
    What do you mean with "doing the USB stuff"?

    BTW: what kind of USB plug is used on the Teensy 3.2? I assume that I need a USB cable between my PC and the Teensy.
    Sorry, I am a complete newbee to Arduino.

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    Senior Member+ MichaelMeissner's Avatar
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    Quote Originally Posted by Papa Echo View Post
    First of all: I don't have the Teensy 3.2 until now, because I want to make sure that it works with my SBUS receiver.
    I want to power it from the USB port. On the back side I see VUSB, but not VIN.

    What kind of switch are you thinking about and where can I order it?
    What do you mean with "doing the USB stuff"?

    BTW: what kind of USB plug is used on the Teensy 3.2? I assume that I need a USB cable between my PC and the Teensy.
    Sorry, I am a complete newbee to Arduino.
    VIN is on the front side. Basically, the 28 outer pins are shown on the front side of the pinout card. The inner pins and solder pads (5 pins at the back of the Teensy, 4 internal through hole solder pins, and the solder pads) are documented on the back side of the pinout card. So if you look at the pinout card, with the USB port facing left, the VIN pin is the top left pin on the outside row, and the VUSB pin is the first inside pin, next to the AGND pin.

    The Teensy 3.2 uses a micro USB-b cable to connect to the host. Make sure you have a data cable that can pass information, and not a power only cable.

    For the simplest case, you would not cut the VIN <-> VUSB connection. Then you can use the VIN pin to get the 5v for your device. There are cases where you might want to cut the direct connection. For example, if you want to power your Teensy with a 3.7 volt lipo battery, you might want to cut the connection, and hook up the battery to VIN, and hook up VUSB to the charger. If you wanted an on/off switch on the Teensy, you could also cut the connection, and then use any on/off switch between VUSB and VIN. It is unfortunate that the VUSB pin is not directly next to the VIN so that you could use a simple 0.1" switch.

    Adafruit has an on/off cable (https://www.adafruit.com/product/1092) that can be used, but they are out of stock right now (and mostly closed down except for essential virus orders). The main secondary distributor that is still open (digikey.com) does not carry this. You could perhaps get a different switch and bend the pins, or use wires to connect to the switch.

    By 'doing the USB stuff' I just meant automatically being powered on when you attach the cable.

    An easier way is to get a USB cable with a switch in it or a USB switch box with an on/off button to turn the Teensy on/off, or just plug the cable and unplug the cable.

    But all of this is secondary to just getting the thing running.

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    Thank you for the comprehensive reply.
    I found a much easier way for the switch. The receiver comes with a cable and a plug. I would just solder cables with a plug to the Teensy board and unplug the receiver, if necessary.
    I just pried around on the pjrc website and found out that the Teensy 4.0 is very similar, but much faster. And the price is almost the same. Is it compatible to the 3.2?

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    Quote Originally Posted by Papa Echo View Post
    Thank you for the comprehensive reply.
    I found a much easier way for the switch. The receiver comes with a cable and a plug. I would just solder cables with a plug to the Teensy board and unplug the receiver, if necessary.
    I just pried around on the pjrc website and found out that the Teensy 4.0 is very similar, but much faster. And the price is almost the same. Is it compatible to the 3.2?
    It depends what you mean by compatible. Many things are the same, but there are a lot of differences. I put together a list where the Teensys are the same across models here:


    Note, in terms of your questions, since you are talking about powering the SBUS with 5 volts, note that you can damage the Teensy 4.0 if any pin gets more than 3.3 volts (other than VIN/VUSB).

    If you have the audio shield, you must use revisions A-C of the audio shield on the Teensy 3.x processors, and revision D of the audio shield on the Teensy 4.0 processor.

    The Teensy 4.0 does have a convenient power off button, where if you use a momentary switch and ground the button for about 15 seconds, the Teensy will turn itself off, until you release the switch, and then press it again for a few seconds.

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    An SBUS receiver usually has 3 wires: ground, +5V and signal. I don't know the power level of the signal, but I think it is below 3V.

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    After more than half a year I want to reopen this thread. Meanwhile I bought the Teensy 4.0 and the SBUS receiver. The SBUS signal wire has an output of 5V and I used two resistors as a voltage divider to get 3.3V. The SBUS signal output is soldered to the input 0. I have loaded the .hex file from the Teensy 3.2 board onto the Teensy 4.0 and I didn't get an error message. In Windows 10, under Settings -> Bluetooth and other devices I can see an "SE Blank RT Family".
    Unfortunately my dongle is not working. What could be wrong?

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