Serial / Baud Rate Reference
Updated Mar 25, 2026
A complete reference for serial communications. The live calculator decodes any serial parameter combination — select your baud rate, data bits, parity, and stop bits to instantly see the full notation, a frame layout diagram, and computed throughput (characters/sec, bytes/sec, KB/s, and overhead percentage).
Includes a standard baud rate reference table from 110 to 921600, a three-way RS-232 / RS-422 / RS-485 comparison with side-by-side cards and a spec table, a flow control reference covering hardware RTS/CTS vs software XON/XOFF vs none, a collapsible DB-9 pinout with DTE/DCE directions, and a Digi device server configuration callout with a ready-to-copy CLI snippet.
Serial Parameter Calculator
Select your serial parameters to decode the shorthand notation, visualize the frame, and calculate effective throughput.
Serial Notation
baud rate
data bits
parity
stop bits
9600 8N1 — 9600 baud, 8 data bits, parity: None, 1 stop bit. Each frame is 10 bits total (1 start + 8 data + 1 stop).
Frame layout:
Effective Throughput
Bytes/sec assumes 8-bit data. Overhead = non-data bits ÷ total frame bits.
Standard Baud Rate Reference
Common baud rates, their typical use cases, and notes. When in doubt, start with 9600.
| Baud Rate | Common Use Case | Notes |
|---|---|---|
| 110 | Legacy teletypes | Historic only |
| 300 | Early modems | Historic only |
| 1,200 | Legacy modems, low-speed sensors | |
| 2,400 | Legacy modems, utility meters | |
| 4,800 | GPS NMEA (older), some meters | |
| 9,600 | Industrial equipment, serial consoles, GPS | Most common default |
| 19,200 | Industrial equipment, PLCs | |
| 38,400 | Cisco console (some platforms) | |
| 57,600 | Moderate-speed serial devices | |
| 115,200 | Serial consoles, Digi devices, Arduino, RPi | Most common high-speed |
| 230,400 | High-speed serial, embedded systems | |
| 460,800 | High-speed, cable-length sensitive | |
| 921,600 | Near-limit for most UART hardware | Very short cables only |
RS-232 / RS-422 / RS-485 Comparison
The three most common serial electrical standards — each suited for different distance, speed, and topology needs.
RS-232
- Signaling
- Single-ended
- Topology
- Point-to-point
- Max Nodes
- 1 driver / 1 receiver
- Max Distance
- ~15m at low speeds
- Max Speed
- ~1 Mbps (short cables)
- Duplex
- Full duplex
- Connectors
- DB-9, DB-25
PC serial ports, console cables, modems, industrial HMIs.
RS-422
- Signaling
- Differential (balanced)
- Topology
- Point-to-multipoint
- Max Nodes
- 1 driver / 10 receivers
- Max Distance
- 1200m (4000 ft)
- Max Speed
- 10 Mbps
- Duplex
- Full duplex
- Connectors
- Terminal block, DB-9
Industrial automation, long-distance serial, some AV equipment.
RS-485
- Signaling
- Differential (balanced)
- Topology
- Multidrop bus
- Max Nodes
- Up to 32 unit loads
- Max Distance
- 1200m (4000 ft)
- Max Speed
- 10 Mbps
- Duplex
- Half (2-wire) or Full (4-wire)
- Connectors
- Terminal block, DB-9
Modbus RTU, DMX512, BACnet, HVAC, Digi serial device servers.
| Property | RS-232 | RS-422 | RS-485 |
|---|---|---|---|
| Topology | Point-to-point | Point-to-multipoint | Multidrop bus |
| Max Nodes | 1 / 1 | 1 driver / 10 recv | 32 unit loads |
| Max Distance | ~15m | 1200m | 1200m |
| Max Speed | ~1 Mbps | 10 Mbps | 10 Mbps |
| Duplex | Full | Full | Half or Full |
| Noise Immunity | Low | High | High |
| Connectors | DB-9 / DB-25 | Terminal / DB-9 | Terminal / DB-9 |
Flow Control Reference
Flow control prevents the receiver from being overwhelmed when the transmitter sends faster than it can process.
Hardware — RTS/CTS
Recommended- Uses dedicated RTS/CTS signal lines — no in-band characters
- Receiver drives CTS low to pause the transmitter
- Reliable and works with binary data
- Requires RTS/CTS wires in cable — check your cable pinout
- Null modem note: RTS and CTS must be crossed between devices
Software — XON/XOFF
Text only- Uses in-band ASCII characters:
XON 0x11(resume) andXOFF 0x13(pause) - No extra wires needed — works on a minimal 3-wire cable
- Do NOT use with binary data — 0x11/0x13 may appear in the data stream
- Suitable for plain text terminals and printers only
None
Use with caution- No flow control — transmitter sends without checking receiver state
- Acceptable when both ends process data fast enough to keep up
- Works fine at low baud rates or when data is infrequent
- Risk of buffer overrun at high speeds or with slow receivers
- Most Digi device servers default to no flow control
Digi Device Server — Serial Configuration Notes
- Default settings: 9600 baud, 8 data bits, no parity, 1 stop bit, no flow control (9600 8N1).
- Golden rule: both ends must use identical serial parameters — mismatched baud rate produces garbled or no data.
- Digi ConnectPort / PortServer CLI example to set a serial port to 115200 8N1:
set serial port=1 baud=115200 databits=8 parity=none stopbits=1 flow=none