Part 03 Accessing physical memory with C++ on a Raspberry Pi.md

Part 03: Accessing physical memory with C++ on a Raspberry Pi

For getting a first idea about how to access the Raspberry Pi hardware from C++ Low Level Programming of the Raspberry Pi in C was a very helpful resource.

The different components of the Rapsberry Pi are accessed through fixed physical memory addresses which are documented in the Peripheral specification. Note that depending on which model of the Rapsberry Pi you use, the base address of the peripheries is different. See Peripheral Addresses for details.

For accessing physical memory locations from user space on linux operating systems you have to access /dev/mem. Access to this file requires root privileges which means you have to run your C++ application with sudo.

Because /dev/mem acts as a file, you would have to use file seek, read and write operations to change the content of a physical memory location. To make things easier, just memory map portions of that file into the address space of your own programm. Afterwards you can simply read and write memory locations through pointers and the operating system will redirect those actions to the physical memory location.

For source code look in the directory user-space/raspberrypi for the following files:

• CPhysicalMemory.hpp / CPhysicalMemory.cpp
• CMemoryMapper.hpp / CMemoryMapper.cpp
• CRaspberryPi.hpp / CRaspberryPi.cpp