I want to use a CH340G USB UART to connect to the console of my raspberry pis - something like this: http://www.ebay.com.au/itm/To-TTL-USB2-06Pin-CH340G-Converter-for-STC-Arduino-PRO-Instead-of-CP2102-PL2303-/191149156465 (sorry for the ebay link, but I could not find anything more permanent. Please comment if you have such a link).

Hooking up TxD, RxD and GND are easy. I want to be able to use the DTR signal to reset the RPi. If I turn on DTR, I want that to go to a pin that will cause the Pi to reset. This makes this little USB UART useful as a low-level device access mechanism, accessing the serial console (and with u-boot, it can hook into the boot process), and a reset line if things go bad.

I do not want a user- or kernel-level mechanism to detect this and do the reset. I'd like it to be at the hardware level so I can reset at any time regardless of the state of the software.

I also do not want to use a watchdog. I would like a crashed Pi to keep its last error message on the console and allow me to reset manually.

How can I hook up the DTR line to do this?

Edit: I have RPi Model B rev 2.0 and RPi2 boards.

  • Also, what's a cool thing I can hook up CTS to for the Pi to signal back to the controller host?
    – camh
    Jul 22, 2015 at 7:09

1 Answer 1


You can use the P6 pins in the Raspberry. Take a look at http://raspi.tv/2012/making-a-reset-switch-for-your-rev-2-raspberry-pi for details.

  • Thanks, but how would I hook up the DTR signal to do that? That page describes a switch. I don't want a physical switch, but a remote reset via raising DTR.
    – camh
    Jul 22, 2015 at 8:39
  • So, Pin1 is ~3V, Pin2 is ground. If I hook up the DTR line to pin 2, it should reset the Pi when I assert DTR... I think. Also, the Pi2 has a similar header called "Run" at the opposite end to the USB connectors.
    – camh
    Jul 22, 2015 at 9:00

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.