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| UART single direction long cable |
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| Doctorandus_P:
@ajb, Bit fuzzy in my head, :=\ didn't do the math, tnx for setting it straight. Optocouplers are just as much overkill as RS-485 drivers, but they are also cheap. (But with cheap optocouplers the 115k2 baud may become problematic). With MIDI an output switches a current / voltage, which goes through an optocoupler at the "other" end of the cable. Because the diode in the optocoupler needs a fair bit of current to turn on this also provides for signal integrity over the cable. It becomes a current loop. By using resistors on both end of the cable you improve robustness against ESD events and accidentally applied external voltages. As a cricuit you can use something similar to: |
| technix:
If you are paranoid with interference, use a stretch of TOSLINK. That is optical transmission, which is immune to EM interference and allow you to break the ground since it is inherently isolated. TOSLINK are those cheap plastic optical fibers used in audiovisual equipment. They are usually specified at 16Mbps or higher, so you can run 115200 bps over that (or even 2Mbps if you dare to) |
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