Compatibility checks
| Driver/Windows support | Use a traceable chipset and vendor driver compatible with the target OS. |
|---|---|
| COM numbering | Old software may accept only COM1–COM4 or store a fixed number. |
| Latency/buffering | USB packet scheduling can affect time-gap protocols or tight polling. |
| Handshake lines | Verify RTS/CTS, DTR/DSR and any nonstandard use. |
| Electrical layer | Confirm real RS232 levels; a USB TTL UART is not equivalent. |
Test the workflow
- Record native-port settings, traffic and timing from a working system.
- Assign a stable low COM number if the application requires it.
- Compare control lines and bidirectional captures under identical operations.
- Test disconnect/reconnect, reboot and sustained transfers.
- Avoid attributing protocol errors to chipset brand without measured evidence.
When native UART hardware is safer
Prefer an industrial/native serial interface when deterministic latency, unusual baud rates, custom control-line use, isolation or safety-critical equipment makes USB behavior unacceptable.
Resolve cable type with null-modem versus straight wiring, establish evidence through traffic capture, and use software development if COM selection/timing must be changed. See the pillar.
Provide adapter hardware IDs, driver version, COM settings, original interface and timing-sensitive symptoms.