Example_USB

Example with TW39 Compact USB Interface

TODO...

Hardware

This is the first approach with a USB to TTL adapter (middle), a DC/DC converter (bottom) and a self-made-board (top) for current regulator, reading and controlling the loop.

Schematics

This can be used with a Windows-PC, Linux-PC, Mac (not tested) and Raspberry Pi.

RTS/CTS Hack for TW39

To decode the TW39 protocol correctly it is necessary to detect a permanent low and high on the RDX pin. The chip (CH340) and drivers can not handle that. The Hack is to use an other input pin (CTS) to detect the states of the line.

Therefore the pin RXD has to be connected to pin CTS of the CH340 chip.

Most PCBs with the CH340 chip do not route the CTS pin to a connector. Use a thin wire to connect the pins 3 and 9 directly on the chip.

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Software

For Installation see SW_Install

This electronic is handles by the software module CH340TTY.

Start the program with arguments -W TTY on Linux:

python3 telex.py -W /dev/ttyUSB0

or on Windows:

python3 telex.py -W COM3

Adapt the com/tty port name to your PC/RPi setup.

???

TODO