RS232 Serial Communication Protocol
An overview of RS232 serial communication protocols, including voltage levels and standard PC interface compatibility.
RS232 is a standard for serial communication transmission of data. It formally defines the signals connecting between a DTE (Data Terminal Equipment) and a DCE (Data Circuit-terminating Equipment).
Technical Specifications
RS232 utilizes bipolar signaling, which distinguishes it from TTL-level serial communication (such as UART).
- Voltage Levels: Uses +12V to -12V signaling.
- Logic High (Mark): -3V to -15V.
- Logic Low (Space): +3V to +15V.
Warning
RS232 voltage levels are incompatible with standard microcontroller UART pins (typically 0V to 3.3V or 5V). Connecting RS232 signals directly to a microcontroller will cause permanent hardware damage. A level shifter (e.g., MAX232) is required for conversion.
Common Applications
RS232 is historically common on PC serial ports (DB9 connectors) and is frequently used in automotive diagnostic interfaces and legacy ECU tuning hardware.
Signal Characteristics
| State | Voltage Range | Logic Level |
|---|---|---|
| Mark | -3V to -15V | 1 |
| Space | +3V to +15V | 0 |
Tip
When troubleshooting communication issues, verify the ground reference between the PC and the target device. RS232 requires a common ground to maintain signal integrity.