RF1-Wire vs. I2C: Interface Protocol Differences Explained
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This article delves into the distinctions between 1-wire and 2-wire (specifically, I2C) interface protocols. We’ll explore the key differences between these communication methods, outlining their strengths and weaknesses to help you choose the right protocol for your application.
The following table summarizes the key differences:
| Specifications | 1 Wire Interface Protocol | 2 Wire Interface Protocol (I2C) |
|---|---|---|
| Number of lines | Uses a single data line and no clock, requiring at least two wires (data and GND). | Uses a clock line and data line, requiring four wires (MISO, MOSI, SCLK, SS). |
| Clock signal | Not required, as each of the slave devices is clocked using an internal oscillator. The oscillator is synchronized to the falling edge of the master. | Requires a separate SCL line. It is low at the START of communication and high at the END of communication. This is referred to as the START and STOP condition. |
| Type of communication | Half-duplex | Full-duplex |
| Hardware complexity | Less | More |
| Software complexity | More | Less |
| Cost | Cheaper (i.e., economical) | Costlier |
| Supply | Parasitic supply (i.e., draws power from the data line) | External supply is needed for its operation. |
| Supply voltage range | Usually from 2.8V (min.) to 5.25V (max.) | +5V or +3.3V or lower |
| Device addressing | 64-bit | Uses 7-bit, 8-bit, or 9-bit device addressing. |
| Modes | Strictly master-slave; multiple slaves are supported in multi-drop mode. | Multi-master is supported. |
| Data rate/speed | 16.3 Kbps (standard mode), 163 Kbps (overdrive mode) | Slower, about 400 Kbps (much faster with faster I2C implementations) |
| Voltage for logic 0 and 1 | Uses CMOS/TTL levels. Logic 0 is represented by 0.8V (max.) and logic 1 is represented by 2.2V (min.). Often represented by variations in pulse width (logic 0 wider, logic 1 narrower), similar to PWM. | Voltage levels are not fixed due to various technologies (NMOS, CMOS, Bipolar). VIL is usually represented by 0.3VDD and VIH is represented by 0.7VDD. |
| Power consumption | Lower | Higher |
| Distance | Longer | Shorter |
| References |
Key Takeaways and Further Exploration
In essence, 1-wire offers simplicity with its minimal wiring, making it suitable for applications where cost is a major constraint and lower data rates are acceptable. However, this simplicity comes at the cost of increased software complexity.
I2C, on the other hand, provides higher speed and multi-master support but demands more wiring and potentially higher power consumption.
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