SPI Communication with Arduino

Introduction
In a previous video, we explored the I2C protocol, which allows a master device to communicate with multiple slave devices. Today, we're going to discuss the SPI protocol and how it can be used with an Arduino board.

The DS3234 IC
We'll be using the DS3234 IC, a real-time clock that automatically keeps track of seconds, minutes, hours, days, dates, months, and years. It also offers two programmable alarms with square wave signal outputs.

Connecting the Arduino to the DS3234 IC
The block diagram of the Arduino's microcontroller shows that it features SPI functionality at pins PB4, 3, 5, and 2. These correspond to digital pins 13, 12, 11, and 10 on the Arduino board.

Understanding the SPI Protocol
The SPI protocol requires a master device to communicate with one or more slave devices. The master device controls the communication process, and the slave devices respond accordingly.

Configuring the SPI Communication
The spark fun sketch configures the SPI communication by setting the chip select pin low, sending an address to the slave device, and then sending data to be written to the addressed register.

Writing Data to the DS3234 IC
The write function sends an address to the slave device, followed by the data to be written. In this case, we're writing to the addressed register to set the current time and date.

Reading Data from the DS3234 IC
To read data from the DS3234 IC, we send an address to the slave device, followed by a dummy byte (in this case, 0x00). The incoming SPI data is then saved in an integer.

Advantages of SPI over I2C
While the I2C protocol allows for multiple slave devices to be connected to a single master device, the SPI protocol offers faster transmission speeds (up to 4 MHz in this case) and is better suited for applications that require high-speed data transfer.

Category Description
Introduction SPI (Serial Peripheral Interface) protocol is a synchronous serial communication interface used for short-distance communication between microcontrollers and peripheral devices.
Background The SPI protocol was introduced by Motorola in the late 1970s as a master-slave communication protocol. It has since become a widely adopted standard for serial communication between microcontrollers and peripheral devices.
Key Features
  • Synchronous serial communication
  • Full-duplex communication (both master and slave can transmit and receive data simultaneously)
  • Single-master, multi-slave architecture
  • Data transfer rates up to several Mbps
Components
  • Master device (usually a microcontroller)
  • Slave devices (peripheral devices such as sensors, displays, and memory chips)
  • MOSI (Master Out Slave In) line for data transmission from master to slave
  • MISO (Master In Slave Out) line for data transmission from slave to master
  • SCK (Serial Clock) line for synchronizing data transmission
Communication Process
  1. The master device initiates communication by sending a clock signal on the SCK line.
  2. The slave devices synchronize their internal clocks with the master clock signal.
  3. Data transmission occurs on the MOSI and MISO lines, with the master transmitting data to the slave(s) on the MOSI line and the slave(s) transmitting data back to the master on the MISO line.

SPI Communication with Arduino
Introduction SPI (Serial Peripheral Interface) is a synchronous serial communication protocol used for short-distance communication between microcontrollers and peripheral devices. In this article, we will explore the basics of SPI communication with Arduino and how to use it in your projects.
What is SPI? SPI is a master-slave protocol, meaning one device acts as the master and controls the data transfer, while the other devices act as slaves and respond to the master. The master device generates the clock signal and initiates the data transfer.
Arduino SPI Pins The Arduino boards have a built-in SPI interface, which is available on the following pins:
  • MISO (Master In Slave Out) - Pin 12
  • MOSI (Master Out Slave In) - Pin 11
  • SCK (Serial Clock) - Pin 13
  • SS (Slave Select) - Pin 10
SPI Modes There are four SPI modes, which determine the clock polarity and phase:
  1. Mode 0: CPOL=0, CPHA=0 (default)
  2. Mode 1: CPOL=0, CPHA=1
  3. Mode 2: CPOL=1, CPHA=0
  4. Mode 3: CPOL=1, CPHA=1
SPI Configuration To configure the SPI interface on Arduino, you need to set the following parameters:
  • Mode: Set the SPI mode using the `SPI_MODE` parameter.
  • Data Order: Set the data order using the `MSBFIRST` or `LSBFIRST` parameter.
  • Bit Order: Set the bit order using the `SPI_BITORDER_MSBFIRST` or `SPI_BITORDER_LSBFIRST` parameter.
SPI Communication To initiate an SPI communication, you need to follow these steps:
  1. Configure the SPI interface using the `SPI.begin()` function.
  2. Set the slave select pin using the `digitalWrite()` function.
  3. Transfer data using the `SPI.transfer()` function.
  4. Release the slave select pin using the `digitalWrite()` function.
Example Code ```cpp const int slaveSelectPin = 10; void setup() { SPI.begin(); pinMode(slaveSelectPin, OUTPUT); } void loop() { digitalWrite(slaveSelectPin, LOW); byte dataToSend = 0x12; byte receivedData = SPI.transfer(dataToSend); digitalWrite(slaveSelectPin, HIGH); delay(1000); } ```

Q1: What is SPI communication? SPI (Serial Peripheral Interface) is a synchronous serial communication protocol used for short-distance communication between microcontrollers and peripheral devices.
Q2: How does SPI communication work with Arduino? The Arduino board acts as the master device, generating a clock signal to synchronize data transmission with the slave device. Data is transmitted in full-duplex mode.
Q3: What are the SPI pins on an Arduino board? The SPI pins on an Arduino board are MOSI (Master Out Slave In), MISO (Master In Slave Out), SCK (Clock), and SS (Slave Select).
Q4: What is the difference between SPI modes? SPI has four modes, determined by the clock polarity (CPOL) and clock phase (CPHA). The modes are: Mode 0 (CPOL=0, CPHA=0), Mode 1 (CPOL=0, CPHA=1), Mode 2 (CPOL=1, CPHA=0), and Mode 3 (CPOL=1, CPHA=1).
Q5: How do I initialize the SPI library on Arduino? The SPI library is initialized using the `SPI.begin()` function. This sets the SCK pin as an output and initializes the SPI module.
Q6: What is the role of the Slave Select (SS) pin in SPI communication? The SS pin is used to select the slave device. When the SS pin is low, the slave device is selected and data transmission begins.
Q7: Can I use multiple SPI devices with Arduino? Yes, you can use multiple SPI devices with Arduino by connecting each device to a separate SS pin. The `SPI.setBitOrder()` and `SPI.setDataMode()` functions are used to configure the SPI interface for each device.
Q8: What is the maximum clock speed for SPI communication with Arduino? The maximum clock speed for SPI communication with Arduino depends on the specific board and the connected devices. Typically, it ranges from a few MHz to tens of MHz.
Q9: Can I use SPI for both input and output operations? Yes, SPI is a full-duplex communication protocol, allowing simultaneous data transmission in both directions (input and output).
Q10: What are some common applications of SPI communication with Arduino? SPI communication with Arduino is commonly used for connecting SD cards, LCD displays, sensors, and other peripheral devices that support the SPI protocol.


Rank Pioneers/Companies Contributions
1 Nick Gammon Developed the first SPI library for Arduino, enabling communication with SPI devices.
2 Paul Stoffregen (PJRC) Created the popular SdFat library for Arduino, which includes SPI support for SD cards.
3 Adafruit Industries Developed a range of SPI-based products and libraries for Arduino, including the Adafruit ILI9341 TFT display library.
4 MikroElektonica (MIKROBUS) Created the MIKROBUS shield, which provides a standardized interface for SPI communication with various sensors and modules.
5 SparkFun Electronics Developed a range of SPI-based products and libraries for Arduino, including the SparkFun Qwiic system.
6 Seeed Technology Created the Grove shield, which provides a standardized interface for SPI communication with various sensors and modules.
7 Digilent Inc. Developed a range of SPI-based products and libraries for Arduino, including the Digilent Pmod system.
8 Espressif Systems (ESP32/ESP8266) Created the popular ESP32 and ESP8266 microcontrollers, which include SPI interfaces and Arduino compatibility.
9 STMicroelectronics (STM32) Developed a range of STM32 microcontrollers with SPI interfaces and Arduino compatibility.
10 NXP Semiconductors (LPC1768/LPC1343) Created the popular LPC1768 and LPC1343 microcontrollers, which include SPI interfaces and Arduino compatibility.


Section Description
SPI Overview The Serial Peripheral Interface (SPI) is a synchronous serial communication interface specification used for short-distance communication, primarily in embedded systems. SPI devices communicate in master/slave mode where the master device initiates the data transfer.
SPI Protocol The SPI protocol uses a master-slave architecture with a single master device and one or more slave devices. The master device generates the clock signal (SCK), while the slave devices receive it. Data is transmitted most significant bit first.
SPI Arduino Pins Arduino boards have a built-in SPI interface, which uses the following pins:
  • MISO (Master In Slave Out) - Pin 12 on most Arduino boards
  • MOSI (Master Out Slave In) - Pin 11 on most Arduino boards
  • SCK (Clock) - Pin 13 on most Arduino boards
  • SS (Slave Select) - Pin 10 on most Arduino boards
SPI Mode The SPI interface can operate in four different modes, defined by the clock polarity (CPOL) and clock phase (CPHA). The modes are:
  • Mode 0: CPOL=0, CPHA=0 - Clock is low when idle, data is captured on rising edge
  • Mode 1: CPOL=0, CPHA=1 - Clock is low when idle, data is captured on falling edge
  • Mode 2: CPOL=1, CPHA=0 - Clock is high when idle, data is captured on falling edge
  • Mode 3: CPOL=1, CPHA=1 - Clock is high when idle, data is captured on rising edge
SPI Arduino Library The SPI library in Arduino provides functions to initialize the SPI interface, transfer data between master and slave devices, and configure the SPI mode. The main functions are:
  • SPISettings(clock, bitOrder, dataMode) - Initializes the SPI interface with specified settings
  • transfer(uint8_t data) - Transfers a single byte of data between master and slave devices
  • beginTransaction(SPISettings settings) - Begins an SPI transaction with specified settings
SPI Arduino Example 
// Master device code
#include 

const int slaveSelectPin = 10;

void setup() {
  pinMode(slaveSelectPin, OUTPUT);
  SPI.begin();
}

void loop() {
  digitalWrite(slaveSelectPin, LOW);
  uint8_t dataToSend = 0x12;
  uint8_t receivedData = SPI.transfer(dataToSend);
  digitalWrite(slaveSelectPin, HIGH);
  delay(1000);
}