USB Rx from GPIO

Question

I'm trying to get Rx from USB via GPIO for reverse engineering. I'll use it for such as keyboard, mouse, USB fax modem etc... I want to get data from USB device and sending data to my another computer. If it's impossible at least give me an idea or alternative way for doing this.

I tried to get keyboard's key presses but I failed at it.

Edit: in Python I already know how to key press or normal input set up but I think i'm lookin for digital input

I need a code block for doing this in Python for ex.

import RPi.GPIO as GPIO
GPIO.setmode(GPIO.BCM)
GPIO.setup(18, GPIO.IN)
while True:
    print(GPIO.input(18))

I connected a keyboard to USB Female and its always returning 1

SMFBE

Answer 1

All apologies for my (deleted) answer about USB using 5V logic. I had assumed this was the case, but when I went to check that I found this, which says high is <=3.6V and low is >=0.3V. I think this should be okay.

However, it also reads:

A USB device pulls one of the data lines high with a 1.5kO resistor. This overpowers one of the pull-down resistors in the host and leaves the data lines in an idle state called "J". The choice of data line indicates a device's speed support; full-speed devices pull D+ high, while low-speed devices pull D- high. In fact the data is transmitted by toggling the data lines between the J state and the opposite K state.

Source: http://www.eeherald.com/section/design-guide/esmod14.html

I am sure USB is a more complicated protocol than your code implements. Some initialization must take place. The keyboard is not simply a dumb serial device, but you have presumed plugging it in that way and hitting a key will cause the levels to shift. You will need to go through the specification to determine what is actually going to happen.

I would guess if the proper initialization does not occur, the device may simply leave the line high and not transmit keystrokes, etc. Notice if you plug a keyboard into a computer, it immediately recognizes it as a keyboard before you hit any keys. How does that happen? How does it know it is not a data stick or camera, etc? It's via the USB protocol, and you have not implemented it.

Answer 2

Um, you need more than what you have got, to connect directly to a USB device as you have tried.

For starters, USB data is carried differentially over a pair of data leads (D+ and D-) and whilst most of the time one is the inverse of the other the voltage levels (Wikipedia link) are 0.0-0.3V (low) and 2.8-3.6 (high) for low- (1.5Mbs) and full-speed (12Mbs) rates - and those are relative to each other - not to ground; high-speed uses ±0.10V (low) 0.36-0.44V (high) but again that is relative to each other NOT to ground so it is quite possible for the individual voltages to be over the 3.3 Volt_max for the GPIO pins!

You have also only connected the Data+ line and not the Data- one but this is largely academic as your current circuit cannot IMHO work.

Don't give up hope yet, though: for your stated aim - to send/share USB with another computer - you may want to look for the usbip package and/or packages containing the phrase "usbredir"...

Answer 3

Above all, there's no such thing as "USB RX". USB is a strictly "Request-Response" protocol, you will never receive a reply without sending a request first. It's also quite complex: each device expects to be configured before it can be used. Even if you managed to generate correct D- and D+ signals, you'd have to implement a USB host controller driver for your approach to work.