Because of this, pin 10 needs to be configured as an OUTPUT, to avoid conflicts in the operation of the library. The SPI library only supports the Arduino as a master device. SPI.begin() // initialize the SPI libraryĭigitalWrite(10, LOW) // set the SS pin to LOWįor(byte wiper_value = 0 wiper_value at the beginning of the sketch. PinMode(10, OUTPUT) // set the SS pin as an output Once the circuit is connected, upload this code to your Arduino: #include This is a standard library that comes packaged with the Arduino IDE software. To utilize the Arduino Uno’s SPI interface, we need to use the SPI library. You’ll learn basic to advanced Arduino programming and circuit building techniques that will prepare you to build any project. If you want to learn more about the Arduino, check out our Ultimate Guide to the Arduino video course. The SS/CS, MOSI, MISO, and SCLK pins are shown in the diagram below: The Arduino Uno has built-in hardware support for SPI communication. We’ll watch changes in the MCP4131’s output resistance on the serial monitor after we send a command via SPI. We’re going to use an Arduino Uno to control an MCP4131 digital potentiometer with SPI. Now let’s demonstrate how to use SPI on an Arduino by building a simple example project. How to Use an Arduino to Control an MCP4131 Digital Potentiometer With SPI If a response from a slave device is expected, the master device will continue to send clock pulses until all of the response data is received at its MISO pin.įor further reading about SPI communication, check out our other article on Basics of the SPI Communication Protocol. The master needs to send enough clock pulses for the data to reach the last slave device in the chain. Similar to the other SPI network configurations, the SS/CS pins are kept LOW for the duration of data transmission. The data sent from the master then flows from one slave to the next in the chain. At the same time, it generates clock pulses at the SCLK pin. The master device then sends data over its MOSI pin to the first slave device in the chain. This will signal all of the slave devices to prepare to receive data at their MOSI pins. In the daisy chain configuration, the master device first pulls the SS/CS pin LOW to initiate communication. Sending Data in a Daisy Chain Configuration The SS/CS pin should be set to LOW to inform the slave that the master will send or request data. Slave Select/Chip Select (SS/CS) – the connection used by the master device to inform the slave device that it will send or request data.Serial Clock (SCLK) – the line that carries the clock pulse generated by the master device.Master In Slave Out (MISO) – the connection for the slave device to send data back to the master device.Master Out Slave In (MOSI) – the connection for the master device to send data to the slave device.Each master and slave device has the following pins: The SPI bus refers to the wires that connect the master device to the slave devices. There can be one or more slave devices in an SPI network. The slave device receives commands from the master device, and sends data back to the master device. There is only one master device in an SPI network. The master device sends data to, and receives data from slave devices. Parts of an SPI NetworkĪn SPI network consists of a master device and one or more slave devices connected on a bus. It should only be used for communication between devices that are less than 10 meters apart. SPI communication isn’t good for transmitting data over long distances. SPI is a type of synchronous serial communication, which means that data transfer is timed with clock pulses. SPI is an acronym for Serial Parallel Interface.
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