Simple asyncronous node.js SPI library for Raspberry Pi (and likely other embedded Linux platforms that provide /dev/spidevN.N).
npm install pi-spi
var SPI = require('pi-spi');
var spi = SPI.initialize("/dev/spidev0.0"),
test = Buffer.from("Hello, World!");
// reads and writes simultaneously
// e.g. jumper MOSI [BCM 10, physical pin 19] to MISO [BCM 9, physical pin 21]
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.
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.
Sets (or gets, if no argument provided) the clock speed in Hz. Defaults to 4e6, i.e. 4MHz. The Pi only supports powers of 2 speeds and faster speeds might get derated a bit.
Sets (or gets, if no argument provided) the "data mode" (clock phase and polarity) to e.g. SPI.mode.CPHA | SPI.mode.CPOL. Default is no flags.
Sets (or gets, if no argument provided) the bit ordering. Default is SPI.order.MSB_FIRST or you can set SPI.order.LSB_FIRST.
Note that this is bit ordering, not bytes — byte ordering is up to your application.
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 (which defaults to outbuffer.length if not provided).
Collects incount bytes while writing as many \0 out.
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.
Frees up the underlying device descriptor if you are no longer using this instance. You will need to SPI.initialize a new instance if you wish to resume communication later.
Copyright © 2013–2019, Nathan Vander Wilt. All rights reserved.
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