Driving an external serial device through arduino uno

Using Arduino Microcontrollers
1

Hi,

I'm having trouble to control a commercial device through serial link using an arduino uno. When I used usb-ttl-converter I can control the device on computer. I noticed that TTL converter transmits +-5V amplitude signal and gets +-9V amplitude response from the device. As it is clear these are harmful values for arduino. Thus I thought to use another max232 to change these high amplitude values; however, TTL converter automatically turned disabled when I started the sample/simple serial transmitter/receiver script. So does anyone has any idea about how to change the serial signal amplitude coming from external device? or how can I control (transmit/receive data) such a device using arduino?

thanks in advance ... :slight_smile:

2

Max232 is the right part to use to convert from rs232 levels to 5v levels

The 5v ttl serial is 0v/5v not +-5v

Its not clear from your post what issue you had with it

3

macellan:
I noticed that TTL converter transmits +-5V amplitude signal and gets +-9V amplitude response from the device.

All Serial Ports works on same voltage level i.e. 5V. If your external device is supporting Serial Port then those pins can easily be interfaced with Arduino.

The thing you need to find is that whether these pins works on Serial Logic or TTL Logic. If it works on TTL Logic then there's no need to use MAX232 but if works on Serial Logic then you need to place single MAX232 between Microcontroller and your Serial Port from external device.