Serial Port Configuration
Serial Port Overview
The BB-400 includes a fully configurable serial port capable of RS-232, RS-422 full duplex, and RS-485 half duplex communication. The protocol is software-selectable through the web interface or configuration file, but hardware jumpers must be set appropriately for termination and biasing.
The serial port is accessible in Linux as /dev/ttySC0.
Hardware Jumper Configuration
Four configuration jumpers inside the enclosure control termination and biasing:
- FT: Full Duplex Termination
- HT: Half Duplex Termination
- B+: Positive Biasing
- B-: Negative Biasing
Park Mode (Default - RS-232)
By default, all jumpers are in the park position for RS-232 operation. RS-422 and RS-485 can operate with jumpers in park mode for short cable runs at lower data rates, but termination becomes mandatory as data rates and cable lengths increase.
Full Duplex Mode (RS-422/RS-485 FD)
For RS-422 or RS-485 full duplex operation with termination, configure the FT jumper and biasing jumpers as required by your network topology.
Half Duplex Mode (RS-485 HD)
For RS-485 half duplex (two-wire) operation, configure the HT jumper and biasing jumpers. Termination resistors match cable impedance to prevent signal reflections, while biasing resistors maintain a known idle state on the bus.
Software Configuration
Serial port parameters are configured via the web interface under Serial settings, or through the BB CLI configuration file. Available settings include:
| Parameter | Options |
|---|---|
| Protocol | RS-232, RS-422, RS-485 Full Duplex, RS-485 Half Duplex |
| Baud Rate | 300 to 921,600 (custom rates supported) |
| Data Bits | 5, 6, 7, 8 |
| Stop Bits | 1, 1.5, 2 |
| Parity | None, Odd, Even |
| Flow Control | None, RTS/CTS, XON/XOFF |