Jane1:
I can easily use Arduino UNO's pin3( TXD) and pin 4( RXD) to be able communicate with another device using UART on that device.
Is it possible to use Arduino Uno so that it can communicate with the device using RS232?
Or must I use voltage level convertor?
Thanks
If what you are trying to interface with indeed uses true RS-232 using bipolar signal voltages, then you will need a TTL to RS232 converter circuit or module. This not only converts the voltage levels correctly but also inverts the logic signals which is also required.
Keep in mind that I have seen devices claiming to have a RS-232 interface but when looking deep into there instruction manual and or datasheet, they are actually using TTL level serial data link. So study carefully what you have and what it actually requires to be able to wire to the arduino serial data pins.
Lefty