Termux (Android) LibUSB-1.0 Python 3 adapter (?)

See USB infos in termux wiki;

List connected USB devices and get ID:

termux-usb -l

Run script (test) with selected device:

termux-usb -r -e ./usbtest_rw1.py.sh /dev/bus/usb/001/002

Setup

Working with Python 3.8.

Theoretically only needs PyUSB. Enganced with IPython, PyFtdi (two formatting functions). Style check and formatting with Flake8 and Black.

Create environment:

python3 -m venv venv
source venv/bin/activate
pip install -r requirements.txt

Android restricts device access, see comments on libusb
Termux only provides a file descriptor (probably queried from Android)
device handles etc. have to be retrieved from a single file descriptor
my module usblib.py provides a function device_from_fd(fd) that extends the PyUSB 1.0 library to provide a Device object from a file descriptor number that can be used as usual

own implementation, guided by:
- pySerial, Timeout object, inspiration for read_until etc., only CP2110 handling (with another backend library hid)
- UsbSerial, command codes & logic flow, adopted from java implementation; flow control untested (how?)
only tested with cp2102 usb-ttl board v4.2 device
- throughput, performance unknown, (seems to work for me)
- flow control (RTS/CTS, DTR/DSR, Xon/Xoff) untested
- does transmission have to be in chunks, with size reported in endpoint info or does the libusb1 library handles this? - works fine with chunks, but may drop in performance for heavy use?
- sync writing?, can a chunk be transmitted in part only (read/write)?
- no interrupting of transmissions
test scripts supplied for various simple situations; tests currently only with connected device
example usage script for DSO138mini data dumps

Hopefully my fix can be adopted in the original PyUSB library. Else, free for all. :-)

See the file "LICENSE" for information on the history of this software, terms & conditions for usage, and a DISCLAIMER OF ALL WARRANTIES.

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