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Damage the Pi Zero, having a usb pad soldered and connect computer?

Posted: Thu Jul 27, 2017 12:53 pm
by zippiz
Hi!

So Im doing a project and got a question, I have a Pi Zero with a USB-controller soldered on the tabs... so what if I connect the micro USB-port to a computer, what would happen?

EDIT: With no power connected to the Zero, just the USB...

1) Damage the computer
2) Damage the Pi
3) Damage the Controller
4) No damage, but you could not use the pad to controll the computer
5) No damage, and controller would work

6) Just dont do this, you could destroy everything, including planet earth!
7) Other

Re: Damage the Pi Zero, having a usb pad soldered and connect computer?

Posted: Thu Jul 27, 2017 1:08 pm
by BMS Doug
I'm speculating:

Pi will not work correctly while connected to both USB controller and computer, The USB can only communicate with one device (such as the USB controller, which is then capable of communicating with more devices) and connecting two at once will mean that neither will work.
adding a switch to the power line for the USB controller might work, turn off the controller before connecting to the PC.

Re: Damage the Pi Zero, having a usb pad soldered and connect computer?

Posted: Thu Jul 27, 2017 1:38 pm
by fruitoftheloom
zippiz wrote:
Thu Jul 27, 2017 12:53 pm
Hi!

So Im doing a project and got a question, I have a Pi Zero with a USB-controller soldered on the tabs... so what if I connect the micro USB-port to a computer, what would happen?

1) Damage the computer
2) Damage the Pi
3) Damage the Controller
4) No damage, but you could not use the pad to controll the computer
5) No damage, and controller would work

6) Just dont do this, you could destroy everything, including planet earth!
7) Other
8) stupid idea - do not do it !

The BCM2835 SoC has a single USB Bus and even with the controller connected further connecting to a PC will not achieve anything, except feasibly damaging either the Zero or PC USB.....

By default the single USB is in Host Mode, whilst your PC is also by default in Host Mode, USB works on Host /Slave.

If you put the Zero in Gadget Mode (similar to OTG) it will become a USB Slave and then the USB Controller which is a USB Slave will not function but your PC will recognise a Slave Device has been plugged in, but will feasibly get confused as 2 Slaves present on the single USB Bus.

Re: Damage the Pi Zero, having a usb pad soldered and connect computer?

Posted: Thu Jul 27, 2017 3:06 pm
by zippiz
fruitoftheloom wrote:
Thu Jul 27, 2017 1:38 pm
zippiz wrote:
Thu Jul 27, 2017 12:53 pm
Hi!

So Im doing a project and got a question, I have a Pi Zero with a USB-controller soldered on the tabs... so what if I connect the micro USB-port to a computer, what would happen?

1) Damage the computer
2) Damage the Pi
3) Damage the Controller
4) No damage, but you could not use the pad to controll the computer
5) No damage, and controller would work

6) Just dont do this, you could destroy everything, including planet earth!
7) Other
8) stupid idea - do not do it !

The BCM2835 SoC has a single USB Bus and even with the controller connected further connecting to a PC will not achieve anything, except feasibly damaging either the Zero or PC USB.....

By default the single USB is in Host Mode, whilst your PC is also by default in Host Mode, USB works on Host /Slave.

BMS Doug wrote:
Thu Jul 27, 2017 1:08 pm
I'm speculating:

Pi will not work correctly while connected to both USB controller and computer, The USB can only communicate with one device (such as the USB controller, which is then capable of communicating with more devices) and connecting two at once will mean that neither will work.
adding a switch to the power line for the USB controller might work, turn off the controller before connecting to the PC.
If you put the Zero in Gadget Mode (similar to OTG) it will become a USB Slave and then the USB Controller which is a USB Slave will not function but your PC will recognise a Slave Device has been plugged in, but will feasibly get confused as 2 Slaves present on the single USB Bus.

My misstake, I was not clear enough. There would be no power to the Pi, just connected using the micro-USB and a computer.

Then what would happen?

Re: Damage the Pi Zero, having a usb pad soldered and connect computer?

Posted: Thu Jul 27, 2017 3:18 pm
by BMS Doug
The PC will output 5V to the Pi's USB circuitry. As the Pi0 doesn't have a complicated power circuit this will power up the pi, with the potential problems listed previously.

Re: Damage the Pi Zero, having a usb pad soldered and connect computer?

Posted: Thu Jul 27, 2017 4:09 pm
by zippiz
BMS Doug wrote:
Thu Jul 27, 2017 3:18 pm
The PC will output 5V to the Pi's USB circuitry. As the Pi0 doesn't have a complicated power circuit this will power up the pi, with the potential problems listed previously.
Ok, I see... thanks to you all for the great input, good to know! =)