SPI

Class: SPI

SPI (Serial Peripheral Interface) is a communication protocol which defines a way to communicate between devices.

• On Tizen, the bus number is defined in this documentation.
• On NuttX, you have to know the number of pins that is defined on the target board module. For more information, please see the list below.
  • STM32F4-discovery

SPI.MODE

The clock polarity and the clock phase can be specified as 0 or 1 to form four unique modes to provide flexibility in communication between devices. The SPI.MODE will specify which one to use (the combinations of the polarity and phase).

• 0 Clock Polarity(0), Clock Phase(0), Clock Edge(1)
• 1 Clock Polarity(0), Clock Phase(1), Clock Edge(0)
• 2 Clock Polarity(1), Clock Phase(0), Clock Edge(1)
• 3 Clock Polarity(1), Clock Phase(1), Clock Edge(0)

SPI.CHIPSELECT

• NONE
• HIGH

The chip select is an access-enable switch. When the chip select pin is in the HIGH state, the device responds to changes on its input pins.

SPI.BITORDER

• MSB The most significant bit.
• LSB The least significant bit.

Sets the order of the bits shifted out of and into the SPI bus, either MSB (most-significant bit first) or LSB (least-significant bit first).

spi.open(configuration, callback)

• configuration {Object}
  • device {string} The specified path for spidev. (only on Linux)
  • bus {number} The specified bus number. (Tizen, TizenRT and NuttX only)
  • mode {SPI.MODE} The combinations of the polarity and phase. Default: SPI.MODE[0].
  • chipSelect {SPI.CHIPSELECT} Chip select state. Default: SPI.CHIPSELECT.NONE.
  • maxSpeed {number} Maximum transfer speed. Default: 500000.
  • bitsPerWord {number} Bits per word to send (should be 8 or 9). Default: 8.
  • bitOrder {SPI.BITORDER} Order of the bits shifted out of and into the SPI bus. Default: SPI.BITORDER.MSB.
  • loopback {boolean} Using loopback. Default: false.
• callback {Function}.
  • err {Error|null}.
  • spibus {Object} An instance of SPIBus.
• Returns: {Object} An instance of SPIBus.

Opens an SPI device with the specified configuration.

Example

var spi = require('spi');
var spi0 = spi.open({
  device: '/dev/spidev0.0'
  }, function(err) {
    if (err) {
      throw err;
    }
});

spi.openSync(configuration)

• configuration {Object}
  • device {string} The specified path for spidev. (only on Linux)
  • bus {number} The specified bus number. (Tizen, TizenRT and NuttX only)
  • mode {SPI.MODE} The combinations of the polarity and phase. Default: SPI.MODE[0].
  • chipSelect {SPI.CHIPSELECT} Chip select state. Default: SPI.CHIPSELECT.NONE.
  • maxSpeed {number} Maximum transfer speed. Default: 500000.
  • bitsPerWord {number} Bits per word to send (should be 8 or 9). Default: 8.
  • bitOrder {SPI.BITORDER} Order of the bits shifted out of and into the SPI bus. Default: SPI.BITORDER.MSB.
  • loopback {boolean} Using loopback. Default: false.
• Returns: {Object} An instance of SPIBus.

Opens an SPI device with the specified configuration.

Example

var spi = require('spi');
var spi0 = spi.openSync({
  device: '/dev/spidev0.0'
});

Class: SPIBus

The SPIBus is commonly used for communication.

spibus.transfer(txBuffer, [, callback])

• txBuffer {Array|Buffer}.
• callback {Function}.
  • err {Error|null}.
  • rxBuffer {Array}.

Writes and reads data from the SPI device asynchronously. The txBuffer and rxBuffer length is equal.

Example

var tx = new Buffer('Hello IoTjs');
var rx = new Buffer(tx.length);
spi0.transfer(tx, function(err, rx) {
  if (err) {
    throw err;
  }
  var value = '';
  for (var i = 0; i < tx.length; i++) {
    value += String.fromCharCode(rx[i]);
  }
  console.log(value);
});

spibus.transferSync(txBuffer)

• txBuffer {Array|Buffer}.
• Returns: rxBuffer {Array}.

Writes and reads data from the SPI device synchronously. The txBuffer and rxBuffer length is equal.

Example

var tx = new Buffer('Hello IoTjs');
var rx = spi0.transferSync(tx);
var value = '';
for (var i = 0; i < tx.length; i++) {
  value += String.fromCharCode(rx[i]);
}
console.log(value);

spibus.close([callback])

• callback {Function}.
  • err {Error|null}.

Closes the SPI device asynchronously.

The callback function will be called after the SPI device is closed.

Example

spi0.close(function(err) {
  if (err) {
    throw err;
  }
  console.log('spi bus is closed');
});

spibus.closeSync()

Closes the SPI device synchronously.

Example

spi.closeSync();
console.log('spi bus is closed');