Linux

Raspberry Pi Linux User Mode GPIO in C++ - Part 3

Wednesday, 30 Sep 2015 - 12:33 +0100 by Ralph McArdell Raspberry Pi, Linux, code, C++, GPIO

The previous instalments[1][2] have described creating the rpi-peripherals[3] library to access general purpose input output (GPIO) on a Raspberry Pi running Raspbian Linux in C++ from user space. They covered creating the phymem_ptr class template that utilises RAII (resource acquisition is initialisation[4]) to manage mapped areas of physical memory, setting up the library project and the implementation of support for basic general purpose input and output of single bit Boolean values, clocks and pulse with modulation (PWM).

Raspberry Pi Linux User Mode GPIO in C++ - Part 2

Wednesday, 29 Jul 2015 - 18:04 +0100 by Ralph McArdell Raspberry Pi, Linux, code, C++, GPIO

Previously[1] I described the initial stage of developing a library called rpi-peripherals[2] to access general purpose input output (GPIO) on a Raspberry Pi running Raspbian Linux in C++ from user land – that is there are no kernel mode parts to the library. The library was built on memory mapping the physical memory locations of the Raspberry Pi’s BCM2835 processor’s peripherals’ control registers using the dev/mem device accessed via a RAII (resource acquisition is initialisation[3]) resource managing class template called phymem_ptr.

Raspberry Pi Linux User Mode GPIO in C++ - Part 1

Thursday, 26 Mar 2015 - 15:22 +0100 by Ralph McArdell Raspberry Pi, Linux, code, C++, GPIO, mmap

I started experimenting with Raspberry Pi GPIO using Python[1][2]. Then the original Gertboard[3] kit was released so I ordered and built one which enabled me to play with BCM2835 peripheral IO beyond basic GPIO. At the time the Gertboard had test and example C code available[4] that, as with the Python case, I felt could be expressed more cleanly. I thought it would be interesting to see what advantages C++, hopefully C++11, features and idioms might provide.

Parallella Problems – Initial Investigations

Monday, 14 Jul 2014 - 11:03 +0100 by Ralph McArdell Parallella, hardware, Linux, code, C

In my last two posts Building a Parallella Mini-Cluster[1] and Bringing Up a Parallella Mini-Cluster – Trials and Tribulations[2] I described constructing a small cluster of 4 Parallella boards[3] into a case with power and cooling and initial steps at getting the cluster up and running. I finished at the point where I knew of the following problems: One board has serious problems when using the Epiphany III chip[4] tending to lock up the whole system or at least the network (as I am connecting over ssh locking up or crashing the network looked the same as locking up the whole system).

Bringing Up a Parallella Mini-Cluster – Trials and Tribulations

Saturday, 12 Jul 2014 - 16:35 +0100 by Ralph McArdell Parallella, hardware, Linux

My previous post Building a Parallella Mini-Cluster[1] dealt with physically building the cluster and ended at the point it could be switched on and off. The next stage is bringing the cluster up to a stable and usable state, and I am sorry to report that it has not been a trouble free ride and tracking down the problems is ongoing as of mid-July 2014. One thing I should mention is that before turning on the power for the first time I installed the provided heat sinks on the Zynq FPGA chips.

Raspberry Pi Linux User Mode GPIO in Python

Saturday, 18 May 2013 - 14:28 +0100 by Ralph McArdell Raspberry Pi, Linux, code, Python, GPIO, sys filesystem

In this article I am going to discuss an alternative approach to using GPIO on a Raspberry Pi in Python to that taken by an early version the RPi.GPIO package[1]. The approach occurred to me in 2012 while making a start at hardware interfacing and programming using a Raspberry Pi with some LEDs, switches and the like that had been collecting dust for 20 to 30 years. To read and write data to the GPIO lines I thought I would start with Python and the RPi.