SPI data transfer sequence in Embedded C - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does SPI stand for and what is its main purpose?

SPI stands for Serial Peripheral Interface. It is used to transfer data between microcontrollers and peripheral devices quickly and efficiently.

beginner

List the four main signals used in SPI communication.

The four main signals are:<br>1. SCLK (Serial Clock)<br>2. MOSI (Master Out Slave In)<br>3. MISO (Master In Slave Out)<br>4. SS (Slave Select)

beginner

Describe the sequence of steps in an SPI data transfer.

1. Master pulls SS low to select the slave.<br>2. Master generates clock pulses on SCLK.<br>3. Data is sent bit-by-bit from master to slave on MOSI.<br>4. Data is simultaneously received from slave to master on MISO.<br>5. After all bits are transferred, master releases SS high to end communication.

intermediate

Why is SPI considered full-duplex communication?

Because data is sent and received at the same time on separate lines (MOSI and MISO), allowing simultaneous two-way communication.

beginner

In SPI, what role does the Slave Select (SS) line play during data transfer?

The SS line tells the slave device when it should listen and respond. Pulling SS low activates the slave, and releasing it high ends the communication.

Which SPI signal carries data from the master to the slave?

A MOSI

B MISO

C SCLK

D SS

MOSI stands for Master Out Slave In, so it carries data from the master to the slave.

What happens when the master pulls the SS line low?

A It sends data to the master

B It stops the clock signal

C It resets the SPI bus

D It selects the slave device to start communication

Pulling SS low tells the slave device to listen and prepare for data transfer.

SPI communication is considered full-duplex because:

A It uses only one wire for data

B Data can be sent and received simultaneously

C It only sends data one way

D It uses a clock signal

Full-duplex means data flows both ways at the same time, which SPI supports using MOSI and MISO lines.

Which signal provides the timing for data transfer in SPI?

A MOSI

B MISO

C SCLK

D SS

SCLK is the serial clock generated by the master to synchronize data transfer.

During SPI transfer, when is the data considered fully sent?

A After all bits are shifted out

B When the clock stops toggling

C When the master pulls SS high

D When MOSI goes low

Data is fully sent after all bits have been shifted out on MOSI and received on MISO.

Explain the step-by-step sequence of an SPI data transfer from start to finish.

Think about how the master controls the communication and how data flows both ways.

Describe why SPI is called full-duplex and how its signals support this.

Consider how data moves on MOSI and MISO at the same time.