In daily bidding projects, it is common to encounter inconsistencies between the technical specifications required by the bidding party and the technical support materials provided by the bidders. At such times, caution is necessary; if the unit issues are not clearly explained, it could lead to disqualification of the bid. What should be done in this case? We can include a clarification in the bidding documents. For example, in a recent bidding requirement from a certain organization, the communication rate for I2C was specified as 100kbit/s, but most manufacturers specify their I2C metrics as 100kbps. What is the relationship between these two? Let us discuss the rate units in I2C communication: kbps, kbit/s, and KHz.
1.I2C Communication Overview
I2C (Inter-Integrated Circuit) bus consists of two lines: the data line SDA and the clock line SCL , used for synchronous communication between devices. The master device controls the SCL clock signal and transmits data to the slave device via the SDA line. It is widely used in electronic devices, such as sensors, displays, and memory devices, which often communicate using the I2C bus.
2.Baud Rate (kbps)
Baud rate is a measure of the data transmission rate in serial communication, with the unit being baud (Baud). One baud means one symbol is transmitted per second (symbols per second). In binary communication scenarios, since one symbol represents one bit of information, the baud rate numerically equals the bit rate, commonly expressed in kbps (kilobits per second). For example, in the standard mode of I2C communication, the baud rate can reach up to 100kbps , which means a maximum of 100,000 symbols can be transmitted per second, indicating that a maximum of 100,000 bits of data can be transmitted per second. However, in complex cases like multi-level modulation, one symbol can carry multiple bits of information, leading to a situation where the bit rate = baud rate × bits per symbol, causing the baud rate and bit rate values to differ.
3.Communication Rate (kbit/s)
Communication rate refers to the number of bits transmitted per second, with the unit being bit/s, commonly expressed in kbit/s (kilobits per second) or Mbit/s (megabits per second). In I2C communication, the communication rate directly reflects the speed of data transmission. For instance, in fast mode, the communication rate of I2C can reach 400kbit/s , indicating that 400,000 bits of data can be transmitted per second. The communication rate of I2C is determined by the frequency of the clock signal and the number of bits transmitted each time, closely related to the baud rate. In the binary communication environment of I2C , the baud rate numerically equals the communication rate (bit rate). For example, when the baud rate is set to 100kbps , the communication rate is also 100kbit/s .
4.Bus Rate (KHz)
In I2C communication, the bus rate generally refers to the frequency of the clock signal on the clock line SCL , measured in Hz, commonly expressed in KHz (kilohertz) or MHz (megahertz). The clock signal is used to synchronize data transmission, with the master device sending clock pulses through the SCL line, and data being transmitted on the SDA line according to the rhythm of the clock pulses. For example, in standard mode, the I2C bus rate can reach 100KHz , indicating that the SCL line generates 100,000 clock pulses per second. Since in I2C communication, one clock pulse typically transmits one bit of data, the bus rate (clock frequency) numerically equals the communication rate (bit rate). For instance, when the SCL clock frequency is 100KHz , it means that 100,000 bits of data can be transmitted per second, which corresponds to a communication rate of 100kbit/s .
5.Summary of the Relationships
In I2C communication, baud rate (kbps), communication rate (kbit/s), and bus rate (KHz) have different units but are closely related in essence. In the binary communication system of I2C , the baud rate numerically equals the communication rate because each symbol carries only one bit of information. The bus rate (clock frequency) determines the rhythm of data transmission, and since one clock pulse transmits one bit of data, its value also equals the communication rate. For example, in standard mode, the I2C bus rate is 100KHz , baud rate is 100kbps , and the communication rate is 100kbit/s ; in fast mode, the bus rate is 400KHz , baud rate is 400kbps , and the communication rate is 400kbit/s . This consistency means that in describing the rates of I2C communication, despite the different units, the conveyed meaning of transmission speed is unified.