How connect the Arduino UNO with serial cable to computer?

Using Arduino Installation & Troubleshooting
#1

Hello all,
I have an new Arduino UNO and he works on USB fine. The ASCII-example sketch also works fine on USB with serial monitor tool.
Now I want the Arduino UNO connected with serial cable to the computer. This serial cable works fine with other devices.
The Arduino UNO has TX,RX and GND (pins) only. I disconnected USB cable and connected TX, RX and GND to the serial cable (TX-RX, RX-TX, GND-GND). I tested with the serial monitor tool, the baud rate and the serial port was right.
Now the ASCII-example sketch do not work.

Question: How is the Arduino UNO connected with/to serial cable to computer that the ASCII-example sketch works fine ?

Thanks for answers.
Dietmar

#2

be aware that the voltage levels of Arduino serial are TTL (0..5V) while a standard serial port of a PC are up to 12V.

You need a level convertor to solve this voltage difference, not using one will damage your duino.

#3

Not only is the voltage too high it also goes to negative 12V.
Plus the fact that the signal level is inverted means you need a converter.
Something like a MAX202 chip or similar.

#4

Thanks, I will use MAX202 …

#5