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Serial FAQ
- What’s the difference between UART, RS-232, RS-485, and TTL?
- UART is a serial protocol; RS-232/RS-485 are physical standards; TTL is low‑level logic. PCs use RS‑232 or USB‑UART; embedded boards often use TTL-UART.
- How do I pick baud rate, data bits, parity, stop bits?
- Match the device. Common baud: 9600/115200. Data bits 8, parity none/even/odd, stop bits 1/2. Mismatch causes garbled data or no link.
- Why can’t my PC see the COM port?
- Check cable/power, drivers, and OS device list. Try another USB cable/port. Ensure the adapter is recognized (CH340, CP2102, FT232).
- USB‑to‑serial chips/drivers to know?
- Popular: CH340, CP2102, FT232. Windows/macOS/Linux often auto‑install; otherwise install vendor drivers.
- How do I wire TTL vs. RS‑232/RS‑485?
- TTL uses TX/RX/GND (3.3V/5V). RS‑232 uses TXD/RXD/GND (± levels). RS‑485 uses A/B differential. Wrong levels can damage hardware.
- HEX vs ASCII, and CR/LF/CRLF line endings?
- ASCII is readable text; HEX is raw bytes. Many frames include control chars. Devices vary: CRLF is common, some use CR or LF only.
- Tips for Modbus or custom protocol debugging?
- Know the frame (start/function/length/check/stop). Build HEX frames, capture bytes, verify checksum and timing when issues arise.
- How to troubleshoot unstable serial links?
- Check grounding, shielding, cable quality/length, baud tolerance, termination, flow control (RTS/CTS), and power/EMI noise.