Can I (mis-)use my USB-to-parallel (printer) cable as UART cable in some way (e.g. sticking some cables in the female parallel output and use them as UART connectors)?


closed as off-topic by Marcus Müller, Bruce Abbott, Dmitry Grigoryev, Michael Karas, Voltage Spike Jan 4 '17 at 17:00

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  • 2
    \$\begingroup\$ No. Have you read the Wikipedia article on UART? \$\endgroup\$ – Marcus Müller Jan 4 '17 at 9:13
  • \$\begingroup\$ yes, but did not understand enough :-) When reading it the question came up, because of RS323, wich I thought might work with my adapter. Shouldn't the conversion be similar? (As question what your "no" would exactly mean) \$\endgroup\$ – Jaleks Jan 4 '17 at 9:15
  • \$\begingroup\$ The UART interface send data serially. It has a TX (transmit) and a RX (receive) pin, and a few optional control lines. On the other hand, parallel interface has 8 data bits and a few additional (different from UART) control lines. Not the same beast at all. So, no. It's like asking whether you can plug an ethernet cable in a USB port. No. It doesn't work. \$\endgroup\$ – dim Jan 4 '17 at 9:21
  • \$\begingroup\$ No, it should not be similar. Rs232 is a serial port, and you have a parallel port adapter. IEEE 1284 (your parallel port, see the Wikipedia article on parallel port) is synchronous, UART has "asynchronous" in its name. \$\endgroup\$ – Marcus Müller Jan 4 '17 at 9:23
  • \$\begingroup\$ So the thing that both have in common are that they are based on electrical signaling. \$\endgroup\$ – Marcus Müller Jan 4 '17 at 9:23

The parallel port connector has pins designated like this: -

enter image description here

And, here's an example of where D2 is used for driving a BJT: -

enter image description here

This basically informs us that the data lines can generally be used as IO lines providing the host has the software to support this. This can lend itself to a form of serial comms (similar to UART) but it will be totally reliant on dedicated software loops reading the data pins. In other words, it doesn't have the specific hardware chips to inform the host that a new byte has arrived and that byte has no detectable errors and all the other bells and whistles you get with those specific UART chips.


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