Teensy 3.5

T

teensy_ino

Well-known member
Hello everyone,

I would like to connect a Teensy 3.5 to an SBC (Radxa Rock 5B) via USB.
The Rock 5B is powered by 12V, the Teensy by 5V via the VIN pin + GND.

The Teensy backside card states: "Cut to separate VIN from USB if using external power / battery."

To be able to use the Teensy on a PC via USB later, I would like to modify only the USB cable.

I read that some people have fried their hardware or destroyed their PC with such modifications...

Hence my question:
  • How do I do it correctly?

  • What needs to be disconnected from the USB cable:
    just +5V or also GND?

  • Are there any ready-made cables for this that don't require any tinkering?

Regards
 
5V needs to be cut. GND has to be connected.

There exist USB cables with a switch which in my experience do not work because the data lines are missing.

I am using a USB hub with power switches for each port to connect Teensy devices with external power and where the trace is not cut. It stays a risk to forget to turn the switch to the off position. I haven't had any problems with this together with powerbanks over all the years. But of course I cannot guarantee that there is a chance to destroy something from the USB part of the motherboard in the PC in the case that the switch is on.

You could also cut the trace on the Teensy and solder connections to the pads for a switch to be able to change it there.

Edit: You may find more useful information here:
 
Hi Tom,

Thanks for your info!

I just looked at the Rock5B USB specifications again:
USB C 5V up to 3A
USB 2.0 5V / 0.5A

According to information from this forum, the Teensy 3.5 needs about 100mA.
Then one of the Rock5B USB ports should easily be enough to power the Teensy.

I'm not a fan of USB power supplies, but I think this has more advantages than disadvantages:
No cutting apart the Teensy's PADs, no homemade USB cable, and of course, no additional 5V power supply...

Thanks for the help with the decision!

Best regards
 
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