How to find the right Serial Cables AI guide
Written by an AI model from its trained knowledge.
What the AI looks for in Serial Cables
- Straight-through versus null-modem
- Use a straight-through cable from a computer to a modem or other DCE device. Use a null-modem cable from computer to computer or to many DTE-style devices. Wrong wiring means transmit and receive never meet, so no data passes.
- Gender and connector
- Check whether each end is DB9 or DB25 and male or female. Cisco-style consoles use an RJ45 rollover cable. Gender changers add bulk and are a frequent source of mistakes.
- USB adapter chipset
- Prefer USB-to-serial adapters that state a genuine FTDI chipset, or a current Prolific chipset with supported drivers. Counterfeit Prolific chips are rejected by current drivers.
- Voltage levels
- RS-232 uses roughly plus and minus 12 V. Microcontroller boards use 3.3 V or 5 V TTL serial. Connecting RS-232 to TTL pins can damage the board. Use a TTL adapter for those boards.
Brands that matter
- FTDI: Reference USB-to-serial chipsets and its own TTL cables.
- StarTech: Null-modem, straight-through and USB serial adapters.
- Tripp Lite: Keyspan USB serial adapters and serial cables.
- Cable Matters: Affordable DB9 cables.
What to avoid
- USB-to-serial adapters that do not name their chipset.
- Connecting an RS-232 port directly to TTL microcontroller pins.
Questions
How do I know if I need a null-modem cable?
If two computers, or two devices of the same type, must talk directly, use null-modem. For a computer connecting to a modem or most lab instruments, use straight-through, unless the device manual says otherwise.