RFI2C vs RS485: A Detailed Comparison of Two Communication Protocols
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This article compares I2C and RS485, highlighting their distinct characteristics and applications. It also provides links for further reading on each interface protocol.
I2C Protocol
I2C (Inter-Integrated Circuit) is a communication protocol that enables one or more master devices to communicate with multiple slave devices on integrated circuits. Similar to SPI, it’s primarily used for short-distance communication within a single device. It requires only two signal lines for data exchange.
RS485 Protocol
RS485 is a predecessor to the RS422 interface. It’s a multi-drop and balanced interface that supports both half-duplex and full-duplex communication modes. In an RS485 network, a single device can control up to 32 other devices.
Binary data is represented as follows:
- Logic 1: B > A by 1.5V (max.)
- Logic 0: A > B by 1.5V (max.)
Here, A and B represent the two wires used in RS485 for transmitting and receiving data.
I2C vs RS485: Detailed Comparison
| Specifications | I2C | RS485 |
|---|---|---|
| Distance | Short distance protocol. | Long distance protocol. Covers 50 feet (@10 Mbps) to 4000 feet (@100 Kbps). |
| Clock | Sends and receives data with respect to a clock signal. | Sends and receives data without a clock signal. |
| Speed | Slower compared to RS485. | Faster compared to I2C. |
| Addressing | Automatically increments the address for data storage. | Manually assigns the address for data storage every time. |
| Multi-master communication | Supported. | Not natively supported. RS485 typically operates in a single transmitter to multiple receiver mode. |
| Pin Designations | Uses SDA (Serial Data) and SCL (Serial Clock) lines. | Uses two transmit (TxD+, TxD-) and two receive (RxD+ and RxD-) lines. |
| Data rate | I2C supports 100 kbps, 400 kbps, 3.4 Mbps. Some variants also support 10 Kbps and 1 Mbps. | 100 Kbps to 10 Mbps |
| Type of communication | Synchronous | Asynchronous |
