spi

SPI

This gem aims to provide a Unified method of talking to SPI devices on a variety of hardware. This is mainly aimed at a range of Small Board Computers (SBCs) such as the Raspberry Pi and C.H.I.P. computers.

Currently only the Linux spidev kernel interface is implimented however the code is designed to make adding other drivers a simple process. It should then be possible to choose the correct driver for the hardware without having to re-write code.

Installation

Add this line to your application's Gemfile:

gem 'spi'

And then execute:

$ bundle

Or install it yourself as:

$ gem install spi

Usage

You may need to enable the SPI device on your hardware and/or load the kernel module. On the Raspberry Pi SPI can be enabled through raspi-cofig On the C.H.I.P. SPI can be loaded by importing the SPI DTB

After doing this you should find one or more devices in /dev

user@device:~ $ ls /dev/spi*
/dev/spidev32766.0

To use the default (SPIdev) driver you can specify

require "bundler/setup"
require "spi"
s=SPI.new(device: '/dev/spidev32766.0')
s.speed=500000
s.xfer(txdata: [0x10,0x00])

Currently SPIdev is the only driver.

Simple Testing of just the SPIdev Driver with an RFM69

require "bundler/setup"
require "spi"
require 'spi/driver/spidev'
s=SPI::Driver::SPIdev.new(device: '/dev/spidev32766.0')
s.speed=500000
s.xfer(txdata: [0x10,0x00])

This should result in a 2 byte array with the 2nd value reporting 36 (0x24)

Enabling SPI

C.H.I.P.

https://bbs.nextthing.co/t/using-spi-on-chip-without-kernel-hack/15395

In simple terms (assuming a more recent (december 2016 or later 4.4 image)

sudo mkdir -p /sys/kernel/config/device-tree/overlays/spi
sudo cp /lib/firmware/nextthingco/chip/sample-spi.dtbo /sys/kernel/config/device-tree/overlays/spi/dtbo

Raspberry Pi

Development

After checking out the repo, run bin/setup to install dependencies. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/m1ari/ruby-spi.