RS232 Serial Sniffer/Monitoring Circuit

I’m having trouble debugging the AVR-to-GSM modem serial communication.

Fortunately, my colleague has made me a circuit to view the communication. Unfortunately, it takes two serial ports just to debug the serial communication while my laptop doesn’t have any serial ports (I use USB-serial converter). So, I was thinking to buy another USB-serial converter, before I was struck by this idea.

Here’s the simplest circuit to debug the RS232 serial communication between two devices:

Using GNU screen to debug your serial port

I’m using Linux, and tools like Window’s Hyperterminal to debug your serial port is rare, difficult to use, unpractical, and I have to live with it =) So, after moving here and there, I finally choose my favorite serial debugger in Linux: GNU Screen.

Here’s some tips to use it for your debugging: