Package Exports

pi-spi

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Readme

pi-spi

Simple asyncronous node.js SPI library for Raspberry Pi (and likely other embedded Linux platforms that provide /dev/spidevN.N).

Example

npm install pi-pi

var SPI = require('pi-spi');

var spi = SPI.initialize("/dev/spidev0.0"),
    test = Buffer("Hello, World!");

// reads and writes simultaneously
spi.transfer(test, test.length, function (e,d) {
    if (e) console.error(e);
    else console.log("Got \""+d.toString()+"\" back.");
    
    if (test.toString() === d.toString()) {
        console.log(msg);
    } else {
        // NOTE: this will likely happen unless MISO is jumpered to MOSI
        console.warn(msg);
        process.exit(-2);
    }
});

Probably requires running node under sudo for SPI permissions, unless you've used Wiring Pi's gpio utility or otherwise adjusted device permissions.

API

spi = SPI.initialize(device)

device will usually be "/dev/spidev0.0" or "/dev/spidev0.0". You will first need to enable the spi-bcm2708 kernel module e.g. these instructions or similar for your platform. As mentioned above, by default this device requires root permissions and so you'll either need to change this or run your script with according privilege.

spi.clockSpeed([speed])

Sets (or gets, if no argument provided) the clock speed in Hz. The Pi only supports powers of 2 speeds and faster speeds might get derated a bit.

TBD: constants for supported speeds

spi.dataMode([mode])

Sets (or gets, if no argument provided) the data mode which is mumble mumble.

TBD: clarify and add OR-able flag constants

spi.bitOrder([order])

Sets (or gets, if no argument provided) the bit (not byte!) ordering. (I think any non-zero integer will flip it to least-significant-bit first but don't quote me on that.)

TBD: clarify and add constants

spi.transfer(outbuffer, incount, cb)

Transfers data for the longer of outbuffer.length or incount bytes. If successfully, the second parameter to your callback will be a buffer of length incount.

spi.read(incount, cb)

Collects incount bytes while writing as many \0 out.

spi.write(outbuffer, cb)

Writes outbuffer, ignoring response bytes.

Note that if there was an error opening the device, the transfer/read/write calls will fail each time called. I may revise the initialize method so to allow you to handle the error better.

Compatibility Note

This library is subject to change as it is intended for compatibility with $somethingElse.

TBD: more details when public

License

TBD: insert BSD-2-Clause text here