What makes SPI faster than I2C protocol [closed]

Question

I know the basic of I2C and SPI communication. As both are synchronous protocol. I wanted to know that what makes SPI faster than I2C. If I am not wrong using I2C we can go used 400kbps while in SPI we can achieve 10mbps also. Does it because of hardware change? This question was asked to me in one of the interview.. Please make me correct if I am wrong.

Depressor

This question appears to be off-topic because it is about hardware, not programming. – Baptlsta

speeds depend on what type of board you are using and how your hardware logic is implemented. There are certain advantages and disadvantages in using one over the other. Selection on what bus type to use depends on what type of communication you need between different peripherals which you want to connect using them. quick2wire.com/articles/i2c-and-spi – Granth

Have a look at this explanation in stackexchange: electronics.stackexchange.com/questions/29037/… E. – Geotectonic

Actually, it's mostly about protocols - granted, low level ones with which hardware people have the most familiarity, but the same issues turn up in network stacks, etc. – Albatross

Still, embedded systems questions that are and the border between hardware and software will get a much better reception at electronics.stackexchange.com. Pure software questions are always on-topic there as well, as long as they are related to embedded systems and low-level programming. – Gabo

Answer 1

I2C is quite involved, supporting multiple masters on the bus. Which causes significant overhead in the bus protocol, an ACK for every byte and intentional delays to arbitrate access to the bus. Also a set maximum bus rate, 100 kHz in the original spec, 400 kHz is common today, additional 10 kHz low-speed and 3.4 Mhz high-speed modes, the 2012 spec defines a 5 Mhz ultra-fast mode.

SPI is much simpler, a single master with no bus protocol beyond a chip select and no set maximum bus rate. If the distances are short then you can go as fast as you dare. Quite fast on an interconnect between chips that are less than an inch apart.

Grogshop

Answer 2

There is an important hardware difference which limits the speed on I2C.

SPI: all lines are driven by the transmitter both high and low. This minimizes the time required for the wire to change states.

I2C: all lines are open-collector which means that the transmitter only drives the line low. When the transmitter releases the line, a resistor connected to Vcc (supply voltage) pulls the light high. However, due to capacitance of the wire and the components, the wire goes to high voltage relatively slowly. Because of this, the clock speed must be reduced to allow time for the lines to "drift" high.

Fernferna

This is correct (and also why it is not a programming question). – Dibucaine

If you don't know the answer it's perfectly alright to assume the difference is in the protocol, while actually the hardware is the main limiting factor. Hence the question is about programming, and the answer is not ;) – Nobility