Serial Port and USB Adapter Issues

Finding Your COM Port

1. Open Device Manager (right-click Start > Device Manager)
2. Expand "Ports (COM & LPT)"
3. Find your serial adapter entry and note the COM port number

USB-to-Serial Adapters

Recommended: FTDI chipset adapters for best compatibility. Prolific and CH340 adapters may have driver issues on Windows 10/11.

Serial Settings

Always use: 9600 baud, 8 data bits, No parity, 1 stop bit, No flow control (9600-8-N-1)

Loopback Test

1. Disconnect serial cable from CallerID device
2. On DB9 connector, jumper pin 2 (RX) to pin 3 (TX)
3. Open terminal (PuTTY) at 9600-8-N-1
4. Type characters — they should echo back
5. If they echo, COM port and cable are working