Tag: arm

Why and how to enable ARM Thumb-2 instruction set in Yocto

by Sami Pietikäinen, posted in Linux, Software

The ARM Thumb-2 instruction set is not a new thing. In fact it was announced already in 2003. Yet, the standard ARM instruction set is often still used because it is the default option, while Thumb-2 could be a better alternative. This post explains why the Thumb-2 can be a better option for many applications and also how to configure it in Yocto build system for Linux kernel, system libraries, utilities and user binaries. Continue reading “Why and how to enable ARM Thumb-2 instruction set in Yocto” →

Access hardware from userspace with mmap – Atmel SAMA5D3x programming mode case study

by Sami Pietikäinen, posted in Linux, Software

I was working with a device that used Atmel SAMA5D3x MCU. Sometimes the devices needed to be re-flashed which required putting the MCU to programming mode. However, the device enclosure needed to be opened and also a jumper wire was needed to do this. Then I realized that it would be possible to enter the programming mode directly from Linux by manipulating boot sequence controller registers in the MCU. Writing a dedicated device driver for this seemed like an overkill so I wrote a simple utility application with mmap instead.

Continue reading “Access hardware from userspace with mmap – Atmel SAMA5D3x programming mode case study” →