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: