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Tag Archives: arm-gcc
Side effects and sequence points; why volatile matters
Director at Feabhas Limited
Co-Founder and Director of Feabhas since 1995.
Niall has been designing and programming embedded systems for over 30 years. He has worked in different sectors, including aerospace, telecomms, government and banking.
His current interest lie in IoT Security and Agile for Embedded Systems.
Niall has been designing and programming embedded systems for over 30 years. He has worked in different sectors, including aerospace, telecomms, government and banking.
His current interest lie in IoT Security and Agile for Embedded Systems.
Latest posts by Niall Cooling (see all)
- Navigating Memory in C++: A Guide to Using std::uintptr_t for Address Handling - February 22, 2024
- Embedded Expertise: Beyond Fixed-Size Integers; Exploring Fast and Least Types - January 15, 2024
- Disassembling a Cortex-M raw binary file with Ghidra - December 20, 2022
Introduction
Most embedded programmers, and indeed anyone who has attended a Feabhas programming course, is familiar with using the volatile directive when accessing registers. But it is not always obvious the ‘whys and wherefores’ of the use of volatile.
In this article, we explore why using volatile works, but more importantly, why it is needed in the first place.
Peripheral register access
If we start with a simple, fictitious, example. Suppose we have a peripheral with the following register layout:
register
width
offset
control
byte
0x00
configuration
byte
0x01
data
byte
0x02
status
byte
0x03
with a base address of […]
Posted in ARM, C/C++ Programming, CMSIS, Cortex
Tagged ARM, arm-gcc, sequence point, side effect, volatile
2 Comments
Peripheral register access using C Struct’s – part 1
Director at Feabhas Limited
Co-Founder and Director of Feabhas since 1995.
Niall has been designing and programming embedded systems for over 30 years. He has worked in different sectors, including aerospace, telecomms, government and banking.
His current interest lie in IoT Security and Agile for Embedded Systems.
Niall has been designing and programming embedded systems for over 30 years. He has worked in different sectors, including aerospace, telecomms, government and banking.
His current interest lie in IoT Security and Agile for Embedded Systems.
Latest posts by Niall Cooling (see all)
- Navigating Memory in C++: A Guide to Using std::uintptr_t for Address Handling - February 22, 2024
- Embedded Expertise: Beyond Fixed-Size Integers; Exploring Fast and Least Types - January 15, 2024
- Disassembling a Cortex-M raw binary file with Ghidra - December 20, 2022
When working with peripherals, we need to be able to read and write to the device’s internal registers. How we achieve this in C depends on whether we’re working with memory-mapped IO or port-mapped IO. Port-mapped IO typically requires compiler/language extensions, whereas memory-mapped IO can be accommodated with the standard C syntax.
Embedded “Hello, World!”
We all know the embedded equivalent of the “Hello, world!” program is flashing the LED, so true to form I’m going to use that as an example.
The […]