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To control the speed of the train, we need to read the voltage on potentiometers. The amount of voltage read will directly equate to how fast the train will go.
Review the datasheets:
Schematic: [click here]
Software: [click here]
Note that in the example programs, there is a "knob test" program that is very handy and will easily test if the knobs are working or not, but it does not affect the OE pin on the TXS0108e, so you'll need to set it manually before running the test program.