Download as PDF, PPTX
Embedded Linux
- 1.
- 2.
- 3. 28.05.18 3 Architectures ● MIPS – 1981 –HDTV, wireless networks, VoIP ● Power Architecture – Networking and telecommunications-related embedded applications ● x86 ● ARM – Sony PlayStation Portable (PSP), Apple iPhone
- 4.
- 5. 28.05.18 5 Embedded Linux ● Whylinux? – Supports a vast variety of hardware devices – Supports a huge variety of applications and networking protocols – Linux is scalable – Linux can be deployed without the royalties – Linux has attracted a huge number of active developers – An increasing number of hardware and software vendors – Supports many programming languages
- 6. 28.05.18 6 Busybox The SwissArmy Knife of Embedded Linux ● Tiny versions of many common UNIX utilities ● Small and efficient single executable file ● Can use as init process ● Useful for cross compile ● Multi call Binary‐call Binary
- 7. 28.05.18 7 uCLinux ● Microcontroller Linux ● NoMMU (Memory Management Unit) ● No virtual memories ● Architecture supported: – ARM Cortex-M – ARC – MicroBlaze – Blackfin – Nios
- 8. 28.05.18 8 Real TimeLinux ● Real-Time kernel patch – by Ingo Molnar – PREEMPT_NONE – PREEMPT_VOLUNTARY – PREEMPT_DESKTOP – PREEMPT_RT
- 9. 28.05.18 9 Storage Options ● NORflash (few MB to a GB) – Expensive – Mapped into the CPU address space – Useful for bootloader ● NAND flash (tens of MB to tens of GB) – Much cheaper than NOR – Higher capacities – Needs a lot of hardware and software support
- 10. 28.05.18 10 Storage Options... ● Managedflash – MMC: Multi Media Card – SD: Secure Digital – eMMC – UFS (Universal Flash Storage)
- 11. 28.05.18 11 Bootloaders ● Initialize thesystem to a basic level ● Loads the operating system kernel
- 12.
- 13. 28.05.18 13 Bootloaders... Name Mainarchitectures supported Das U-Boot ARC, ARM, Blackfin, Microblaze, MIPS, Nios2, OpenRiec, PowerPC, SH Barebox ARM, Blackfin, MIPS, Nios2, PowerPC GRUB 2 X86, X86_64 Little Kernel ARM RedBoot ARM, MIPS, PowerPC, SH CFE Broadcom MIPS YAMON MIPS
- 14. 28.05.18 14 UEFI ● Universal ExtensibleFirmware Interface ● The processor loads the platform initialization firmware ● load an EFI boot manager from the EFI System Partition (ESP) ● UEFI boot manager – systemd-boot – Tummiboot
- 15. 28.05.18 15 Initramfs ● Ramfs isa very simple filesystem that exports Linux's disk caching mechanisms ● A dynamically resizable RAM-based filesystem ● gzipped "cpio" format archive ● Linked into the linux kernel image
- 16. 28.05.18 16 Device Tree ● ARMdoes not come with any hardware information ● A flexible way to define the hardware components ● Loaded by the bootloader and passed to the kernel
- 17.
- 18. 28.05.18 18 Device TreeExample serial@4806c000 { compatible = "ti,dra742-uart", "ti,omap4-uart"; reg = <0x4806c000 0x100>; interrupts = <0x0 0x44 0x4>; ti,hwmods = "uart2"; clock-frequency = <0x2dc6c00>; status = "disabled"; dmas = <0xb3 0x33 0xb3 0x34>; dma-names = "tx", "rx"; };
- 19. 28.05.18 19 Pinmux ● Different embeddedprojects deal with different components ● We cannot attach an I2C device to a pin that follows the protocol of the SPI bus ● We cannot attach an analog sensor to the GPIO pin ● It is not possible to have that many CPU pins ● share the functionalities of available pins
- 20. 28.05.18 20 Toolchains ● Set oftools that compiles source code into executables – Compiler – Linker – Run-time libraries ● Standard GNU toolchain components: – Binutils: A set of binary utilities including the assembler and the linker – GNU Compiler Collection (GCC): compilers for C, C++, Objective-C, Java, Fortran, Ada, Go – C library: A standardized application program interface (API) based on the POSIX specification
- 21. 28.05.18 21 Toolchains... ● Native: toolchainruns on the same type of system ● Cross: toolchain runs on a different type of system than the target Linaro, ( h t t p s ://w w w . l i n a r o . o r g / ) crosstool-NG
- 22. 28.05.18 22 Application BinaryInterface (ABI) ● Guarantees that the libraries exist on all compliant machines ● Ensures the integrity of the interface
- 23. 28.05.18 23 Application ProgramInterface (API) ● glibc: it is the most complete implementation of the POSIX API ● musl libc: a small and standards-compliant alternative to GNU libc ● uClibc-ng: developed to work with uClinux
- 24. 28.05.18 24 Application ProgramInterface (API)
- 25.
- 26. 28.05.18 26 Static &Dynamic Compiling
- 27. 28.05.18 27 Yocto ● Tools andmethods to help you create custom Linux- based systems ● The Yocto Project is more than a distribution ● Main Components: – glibc – BusyBox – matchbox (for the windowing system)
- 28. 28.05.18 28 Other ProgrammingLanguages ● C++/Qt ● Python ● Golang ● Node.js ● Lua ● Scratch ● Java ...
- 29.