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Seems there are plenty of questions relating going in the opposite direction, but I couldn't find anything that really told me if I could do this..

I have one of these https://uk.rs-online.com/web/p/serial-converters-extenders/6877806/ for connecting to RS232 devices and I have a need to connect to a device using a USB-TTL adaptor (one of these https://www.dimensionengineering.com/products/sabertooth2x60)

It seems that the Sabertooth only uses RX, TX and GND (pins 2,3, and 5) and I don't need any of the other wires. I'm not 100% sure on what voltage sits on pins 2 and 3 of an RS232 connector - I assume if it were more than 5v then that wouldn't be ideal for TTL!

Can anyone give me a pointer as to whether this will work or not? I don't have a reason to not buy a specific TTL adaptor, apart from I'd rather not do it if I don't have to!

Thanks in advance

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    \$\begingroup\$ You would need to buy or build an inverting RS232<>logic level translator. Today it's much easier to source a USB<>TTL UART device than such an translator on its own, so unless you happen to have an MAX232 type part in your bin, there's really no reason to go with a clunky translator solution and not simply use the right tool for the job. \$\endgroup\$
    – Chris Stratton
    Commented Nov 9, 2020 at 17:11
  • \$\begingroup\$ You should've put this as an answer ;) Thanks for the explanation \$\endgroup\$
    – BoYeo
    Commented Nov 17, 2020 at 13:43

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The RS232 cable you show will produce RS232 signal levels (+/-3V minimum) and may potentially damage the input to your motor driver board. Choose a USB to serial TTL cable such as this to provide the right signal levels. enter image description here

There are many USB-Serial TTL cable available as it's a very common need. The only issue you need to consider is that RS232 is designed to provide viable signal levels at typically 15 meters (depending on the baud rate) whereas TTL signals (depending on the TTL driver used) may only be viable for 1-2 meters.

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  • \$\begingroup\$ Thanks Jack, that's very helpful and made me realise there was a bit more that I needed to understand about TTL. \$\endgroup\$
    – BoYeo
    Commented Nov 17, 2020 at 13:44
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No, the RS-232 serial cable is not compatible with the TTL level serial port of the device.

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