I'm interested in knowing which is faster, Serial communication or I2C.

So far I have the following two snippets of information that I have found while doing a bit of research.

Serial communication

Bit rates commonly supported include 75, 110, 300, 1200, 2400, 4800, 9600, 19200, 38400, 57600 and 115200 bit/s (https://en.wikipedia.org/wiki/Serial_port#Speed)

I2C communication

The speed grades (standard mode: 100 kbit/s, full speed: 400 kbit/s, fast mode: 1 mbit/s, high speed: 3,2 Mbit/s) are maximum ratings. (http://www.i2c-bus.org/speed/)

So based on this information I've concluded that the fastest common bit rate used for the serial communication is 115200 bits/s. This seems to be significantly lesser than the bit rates for I2C, which appear to start at 100 kbit/s which equates to 100000 bits/s.

I'm hoping someone can just confirm that these are in fact correct. Is I2C significantly faster than serial communication?

1 Answer 1


There is no real comparison, these are designed for different purposes.

Serial communication is designed for long distance communication. I have used it over 1000km. There are often speed/distance tradeoffs depending on the communication medium. Getting 56kbps is a challenge over copper phone lines, but it can be used at rates over 1Mbps, although generally you would not use asynchronous serial for these purposes.

I²C is an inter chip protocol, typically used to communicate between devices on the same PC board, or at least adjacent boards. Due to the open drain lines the speed is limited by capacitance. Initially speeds of 100kbps were used, later 400kbps. The standards have higher speeds, but you wouldn't get these on a Pi, and these speeds are designed for very short distance inter-chip communication.

  • Over 1000 km?! Is that really possible?
    – 10robinho
    Aug 25, 2015 at 13:46
  • @10robinho Yes. We had a number of computer terminals in Sydney, connected at 1200 baud via a multiplexor to a 9600 baud modem to computer centre in Melbourne. It had errors, so I replaced with a statistical multiplexor.
    – Milliways
    Aug 26, 2015 at 0:52

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