Can an SPI slave initiate a communication?

A slave can’t initiate communication and specifically the slave can’t change the RW flag in any way. Both SPI and I2C only allow the master to initial communication.

Why would we want to use I2C over SPI for a peripheral that can communicate using both?

I2C supports multiple devices on the same bus without any additional select lines (work on the basis of device address). SPI requires additional signal (slave select lines) lines to manage multiple devices on the same bus. I2C is better for long-distance. SPI is better for a short distance.

Can slave send data to master in I2C?

Both master and slave can transfer data over the I2C bus, but that transfer is always controlled by the master.

How does SPI communication work?

SPI is a full-duplex interface; both master and slave can send data at the same time via the MOSI and MISO lines respectively. During SPI communication, the data is simultaneously transmitted (shifted out serially onto the MOSI/SDO bus) and received (the data on the bus (MISO/SDI) is sampled or read in).

Why is I2C less susceptible to noise than SPI?

One advantage not yet mentioned of SPI over I2C is that all SPI wires are unidirectional and are always driven high or low. This allows much faster communication than is possible with I2C, reduces susceptibility to noise, and allows simple gates to be used as repeaters.

How could a slave send the data to the master in I2C while the master is communicating with another slave?

Addressing : The address frame is the first frame after the start bit. The address of the slave with which the master wants to communicate is sent by the master to every slave connected with it. The slave then compares its own address with this address and sends ACK.

Can SPI have multiple masters?

Both single-master and multi-master protocols are possible in SPI. But the multi-master bus is rarely used and look awkward, and are usually limited to a single slave. The SPI Bus is usually used only on the PCB. There are many facts, which prevent us from using it outside the PCB area.

How many slaves can be connected in SPI?

This means the number of pins required on the master will increase as the number of connected slaves increases. It is typical for a SPI master to control two to three slaves and not more.