Class Name



Opens an SPI interface as master

Serial Peripheral Interface (SPI) is a serial bus, commonly used to communicate with sensors and memory devices. It uses four pins: MOSI (Master Out Slave In), MISO (Master In Slave Out), and SCLK (clock signal) - those three are shared among all devices on the bus - as well as one or more SS (Slave Select) pins, that are used for the master to signal to the slave device that it is the desired respondent for the transmission.

The "master" device initiates a transfer by pulling the SS pin of the "slave" low, and begins outputting a clock signal. In SPI, both the "master" as well as the "slave" device output data at the same time. It is hence not possible to read data without writing some (even if it means outputting zeros or other dummy data).

There are multiple possible configuration settings for SPI, see settings() for details.

This library supports multiple SPI objects making use of the same SPI interface.


  • import*;
    SPI adc;
    void setup() {
      adc = new SPI(SPI.list()[0]);
      adc.settings(500000, SPI.MSBFIRST, SPI.MODE0);
    void draw() {
      // read in values over SPI from an analog-to-digital
      // converter
      // dummy write, actual values don't matter
      byte[] out = { 0, 0 };
      byte[] in = adc.transfer(out);
      // some input bit shifting according to the datasheet
      int val = ((in[0] & 0x1f) << 5) | ((in[1] & 0xf8) >> 3);
      // val is between 0 and 1023


  • SPI(dev)


  • devdevice name