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A homebrew Teletype current loop to RS-232 interface in action
A quick video of a homebrew opto-isolated RS-232 to 20 mA current loop adapter in operation.
The serial protocol analyzer sends a string of U*, waits a few ms, sends CRLF, then waits a few ms, and repeats. This is because U and *, with 7-bit even parity, represent binary 01010101 and 10101010, so every bit is inverted with every character. This tends to show "sticky" bits.
The lighting is terrible because I'm in my garage, at night, with the top for my Jeep between me and the light. Sorry.
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By A quick video of a homebrew opto-isolated RS-232 to 20 mA current loop adapter in operation.
The serial protocol analyzer sends a string of U*, waits a few ms, sends CRLF, then waits a few ms, and repeats. This is because U and *, with 7-bit even parity, represent binary 01010101 and 10101010, so every bit is inverted with every character. This tends to show "sticky" bits.
The lighting is terrible because I'm in my garage, at night, with the top for my Jeep between me and the light. Sorry.