spi-node

Communicate with devices using SPI directly from your Node.js app. Data transfers are executed asynchronously in their own thread. Supports mock data transfers on machines without SPI support for easy local development. Uses Node's now-stable N-API for native addon support. Written in Typescript.

Installation

To install:

npm install --save spi-node

When installing, the native binaries will be rebuilt and added to your project's /build directory. If installing on a machine without SPI support, you'll see this warning from the compiler:

warning: "SPI not supported on this machine" [-W#warnings]

Not a problem, you can programatically opt-in to using mock data transfers by overriding the underlying transfer function.

Usage

[TODO: Add MCP3008 example]

API

The spi-node package exports the following:

import {
  Flags,
  Mode,
  Order,
  SPI,
  Settings,         // TS type
  SpiAddon          // TS type
  TransferCallback, // TS type
  TransferConfig,   // TS type
  TransferFunction, // TS type
} from 'spi-node';

Flags Enum

Flags is an enum of the underlying flags used to set an SPI channel's mode. You (probably) won't need to use Flags directly as they're built into the values of Mode.

enum Flags {
  CPHA = 0x01,
  CPOL = 0x02
}

• Flags.CPOL: If set, sets clock polarity such that the leading edge of the clock cycle is a falling edge.
• Flags.CPHA: If set, data is read on the leading edge of the clock cycle.

Mode Enum

Mode is an enum of the four possible SPI modes, which are just permutations of the Flags.

enum Mode {
  M0 =	0 | 0,
  M1 =	0 | Flags.CPHA,
  M2 =	Flags.CPOL | 0,
  M3 =	Flags.CPOL | Flags.CPHA,
}

The default mode of an SPI instance is Mode.M0.

Order Enum

Order is an enum whose values set the bit order of data transferred over an SPI connection.

enum Order {
  MSB_FIRST = 0,
  LSB_FIRST = 1,
}

The default order of an SPI instance is Order.MSB_FIRST.

SPI Class

[TODO: Add descriptions]

Static properties & constructors

Property SPI.spiSupported: boolean

...

Constructor SPI.fromDevicePath(path: string)

...

Constructor SPI.fromFileDescriptor(fd: number)

...

Properties

mode: Mode

...

order: Order

...

speed: number

...

transferOverride: TransferFunction | null

...

Methods

write(dataIn: Buffer): Promise<Buffer>

...

read(readcount: number): Promise<Buffer>

...

transfer(dataIn: Buffer, readcount: number): Promise<Buffer>

...

close(): void

...

Chainable setter methods

All of the properties of an SPI instance can be set using chainable setter methods, allowing you to instantiate and configure an SPI connection in one go:

const spi = SPI.fromDevicePath('/dev/spidev0.0')
  .setMode(Mode.M0)
  .setOrder(Order.MSB_FIRST)
  .setSpeed(1e7)
  .setTransferOverride(dataIn => Promise.resolve(dataIn)); // jumper MISO/MOSI