I'm trying to get a MCU with a db9 female serial out port (using RS422 protocol) to communicate with a CY8CKIT-050 PSoC® 5LP Development Kit (running a microcontroller).

The development board comes with a db9 female RS232 port and already has the necessary circuitry to process the serial signal (MAX3232CDR level shifter, software configurable UART).

The development kit also has a general SCB UART (also configurable) where I can simply specify pins on the microprocessor as the Rx, Tx, etc. However, I would need to measure the differential signals of the RS422 from the MCU, level shift to TTL voltage levels, etc.

Because the board already has RS232 functionality implemented, I thought it would be easier to use a RS422 (from the MCU) to RS232 (to the PSoC board) converter. However, almost all the converters I could find are RS232 to RS422. Are these reversible?

For instance, the CON-422-PIE datasheet specifies the male db9 end as the "RS232 end" and the female db9 end as the "RS422 end".

If not, does anyone know of good RS422 to RS232 converters?

edit: I want the male end to be RS422 and the female end to be RS232.

  • 13
    \$\begingroup\$ Do you know, serial comm has Tx and Rx, right? One side is both receiving and transmitting, and the other side is receiving and transmitting. So... Can it be non-reversible? \$\endgroup\$
    – Eugene Sh.
    Jul 21, 2016 at 13:35
  • \$\begingroup\$ linear.com/parametric/Multiprotocol_Transceivers \$\endgroup\$ Jul 21, 2016 at 13:36
  • \$\begingroup\$ @eugene Yes, however RS422 uses a Rx+/Rx-, Tx+/Tx- wiring and the converter I mentioned has specific pinouts on the male/female sides. Though, I guess I could use a serial gender changer, but even then, the pinouts may not match with the devices. This is why I wanted to make sure. And thanks for the link peter, I will look into it. \$\endgroup\$
    – Patrick
    Jul 21, 2016 at 14:10
  • \$\begingroup\$ @Patrick The pinouts are not guaranteed by any (global) standard. \$\endgroup\$
    – Eugene Sh.
    Jul 21, 2016 at 14:13
  • 2
    \$\begingroup\$ Again. What is "reversible" for you? I guess at this point you understand, that the "RS232-to-RS422" converter is in the same time a "RS422-to-RS232" converter. But no, you can't connect the RS-232 endo to the RS-422 connector. Unless the converter has some special jumper settings to reconfigure internal connections. \$\endgroup\$
    – Eugene Sh.
    Jul 21, 2016 at 14:26

2 Answers 2


Yes, they are reversible.

1). 232Rx <= 422Tx.

2). 232Tx => 422Rx.

This is what, generally, the converter pinouts say. The first line converts 422 to 232 and vice versa for the second.


Should be, but you may need to procure null modem/crossover cables to ensure the tx and rx pins are properly connected.


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