What Is I2c Clock Stretching? (Solution found)

Clock stretching is one of the most powerful features of the I2C protocol. Clock stretching means that holding the clock to 0 or ground level. The moment clock is kept low, then the whole I2C interface pauses until the clock is given up to its normal operating level.


  • Clock stretching allows an I2C slave device to force the master device into a wait state. A slave device may perform clock stretching when it needs more time to manage data, such as store received data, or prepare to transmit another byte of data. This typically occurs after the slave device has received and acknowledged a byte of data.

What is clock signal in I2C?

I2C is a serial communication protocol, so data is transferred bit by bit along a single wire (the SDA line). Like SPI, I2C is synchronous, so the output of bits is synchronized to the sampling of bits by a clock signal shared between the master and the slave. The clock signal is always controlled by the master.

What is clock arbitration I2C?

During the transfer, the masters constantly monitor SDA and SCL. If one of them detects that SDA is low when it should actually be high, it assumes that another master is active and immediately stops its transfer. This process is called arbitration.

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What is I2C clock speed?

The standard clock (SCL) speed for I2C up to 100KHz. Philips do define faster speeds: Fast mode, which is up to 400KHz and High Speed mode which is up to 3.4MHz. All of our modules are designed to work at up to 100KHz.

What is clock synchronization in I2C?

Clock synchronization is performed using the wired-AND connection of I2C interfaces to the SCL line. In this way, a synchronized SCL clock is generated with its LOW period determined by the device with the longest clock LOW period, and its HIGH period determined by the one with the shortest clock HIGH period.

How do I stop my clock from stretching?

Generally, the effective way to avoid clock stretching is enhancing the system clock of the MCU to reduce the time the ISR takes to execute, but this method is limited by the maximum speed of the MCU.

What is a clock signal in electronics?

In electronics and especially synchronous digital circuits, a clock signal (historically also known as logic beat) oscillates between a high and a low state and is used like a metronome to coordinate actions of digital circuits. A clock signal is produced by a clock generator.

How does I2C multimaster work?

There are I2C environments where multiple masters are driving the bus. If two devices start to communicate at the same time the one writing more zeros to the bus (or the slower device) wins the arbitration and the other device immediately discontinues any operation on the bus.

What is difference between I2C and SPI?

What is the difference between I2C vs SPI? I2C is half-duplex communication and SPI is full-duplex communication. I2C supports multi-master and multi slave and SPI supports single master. I2C is a two-wire protocol and SPI is a four-wire protocol.

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How does I2C arbitration work?

In this method of arbitration, both controllers are transmitting data at the same time. The controller that matches the wired-AND result for SDA is the controller that wins arbitration. The controller that is disrupted by the wired-AND result for SDA stops transmission and releases the I2C bus.

Why is I2C slow?

This is because I2C uses an address system and a shared bus = many different devices can be connected using the same wires and all data are transmitted on a single wire and have a low pin count. However, the tradeoff for this simplified wiring is that it is slower than SPI.

How Slow Can I2C go?

Common I2C bus speeds are the 100 kbit/s standard mode and the 400 kbit/s fast mode. There is also a 10 kbit/s low-speed mode, but arbitrarily low clock frequencies are also allowed.

What is meant by clock synchronization?

Clock synchronization is a topic in computer science and engineering that aims to coordinate otherwise independent clocks. Even when initially set accurately, real clocks will differ after some amount of time due to clock drift, caused by clocks counting time at slightly different rates.

Who generates clock in I2C?

2 Answers. According to me 1) In I2C protocol CLOCK ( on SCL pin) will always generated by MASTER device. SLAVE will work according to it either it receive the DATA ( on SDA pin ) or it send the DATA. SLAVE can’t generate the CLOCK.

What is wired and logic in I2C?

Advanced Member level 5. wired AND is a connection method in which the output of two AND gates is connected together directly and this connection acts like a AND gate. for details see morris mano – digital design

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