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sgjava

User Space IO is Python 3 and Java 8 bindings for user space GPIO, SPI, I2C, PWM and Serial interfaces

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https://github.com/sgjava/userspaceio

 

After a lot of work and testing I have produced the User Space IO project! It provides Python 3 and Java 8 bindings for Linux user space GPIO, SPI, I2C, PWM and Serial interfaces. This allows cross SBC and cross language development using a common API. I took two best of breed C APIs for Linux user space libgpiod and c-periphery and produced CFFI bindings for Python and JNA bindings for Java. Since all the bindings closely match the C API it's easy to move from language to language. The side effect of using the Java library is that it should work with many different JVM based languages. How about creating your programs in Kotlin or Scala for instance?

 

GPIO access uses the new gpiod interface and not the deprecated sysfs interface using libgpiod v1.1 (head from git repo). GPIO, SPI, I2C and serial interfaces expose all the low level functionality. I have added some helper methods for handling repetitive functions like building I2C messages, reading words from two registers, etc. You can of course go as low level as you need to. Please use Github to post any issues, pull requests, etc. I have tested Nano Pi Duo for 32 bit and NanoPi Neo +2 for 64 bit compatibility. I'll test more SBCs as I have time. Also, I have deleted https://github.com/sgjava/libgpiod-extra since User Space IO supersedes it.

 

Based of some of the questions I had in the past please note the following:

  • gpiod_ctxless_event_loop_multiple can handle GPIO interrupts
  • Miscellaneous GPIO request flags GPIOD_LINE_REQUEST_FLAG_OPEN_DRAIN, GPIOD_LINE_REQUEST_FLAG_OPEN_SOURCE, GPIOD_LINE_REQUEST_FLAG_ACTIVE_LOW
  • Non-root access using rc.local.

Demo program using hardware PWM to flash LED:

 

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Sorry to jump in on this only now (because I only started some weeks ago in trying to bring some gpio-spi stuff to work.

This general SBC library approach looks very interesting to me, and I wonder how experienced GPIO/HW/SW technicians see it? Would it deserve more attention? Or had it some drawbacks because it can't be so low level and direct as device tree, libmraa ecc... ?

 

I saw the request to post issues on the github repo, but I believe this is not an issue but more a request for better understanding.

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The main thing for me is I wanted something more portable than RPi.GPIO, so that I can run  the same code on multiple SBCs without coding to a Pi specific API. Plus I wanted to cover the JVM in addition to Python 3 and C. Now I can pick what language makes sense in the context of the project instead of the API driving that (i.e. RPi.GPIO == Python only). Secondly, by using libgpiod for GPIO I'm insulating myself from all the low level coding and making GPIO portable.

 

To me it depends on the project. If I'm doing something from scratch (which I usually am) then I will gravitate to my library since I can port it to a different language or SBC easily. If something I'm working on has a RPi.GPIO or WiringPi dependency then I'll probably use those to save the effort and not reinvent the wheel. If I use luma.oled for instance then It's going to be a Python project. I can use Userspace IO's Python API for GPIO in addition to driving a OLED display with luma.oled.

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