نشست ۱۴۵ شیرازلاگ با ارائه امین خزاعی

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IoT Hardware

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Architectures
●
MIPS
– 1981
– HDTV, wireless networks, VoIP
●
Power Architecture
– Networking and telecommunications-related embedded
applications
●
x86
●
ARM
– Sony PlayStation Portable (PSP), Apple iPhone

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Operating Systems

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Embedded Linux
●
Why linux?
– 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

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Busybox
The Swiss Army Knife of Embedded Linux
●
Tiny versions of many common UNIX utilities
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Small and efficient single executable file
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Can use as init process
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Useful for cross compile
●
Multi call Binary‐call Binary

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uCLinux
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Microcontroller Linux
●
No MMU (Memory Management Unit)
●
No virtual memories
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Architecture supported:
– ARM Cortex-M
– ARC
– MicroBlaze
– Blackfin
– Nios

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Real Time Linux
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Real-Time kernel patch – by Ingo Molnar
– PREEMPT_NONE
– PREEMPT_VOLUNTARY
– PREEMPT_DESKTOP
– PREEMPT_RT

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Storage Options
●
NOR flash (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

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Storage Options...
●
Managed flash
– MMC: Multi Media Card
– SD: Secure Digital
– eMMC
– UFS (Universal Flash Storage)

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Bootloaders
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Initialize the system to a basic level
●
Loads the operating system kernel

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Bootloaders...

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Bootloaders...
Name Main architectures 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

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UEFI
●
Universal Extensible Firmware 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

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Initramfs
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Ramfs is a very simple filesystem that exports
Linux's disk caching mechanisms
●
A dynamically resizable RAM-based filesystem
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gzipped "cpio" format archive
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Linked into the linux kernel image

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Device Tree
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ARM does not come with any hardware
information
●
A flexible way to define the hardware
components
●
Loaded by the bootloader and passed to the
kernel

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Device Tree...

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Device Tree Example
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";
};

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Pinmux
●
Different embedded projects 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

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Toolchains
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Set of tools 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

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Toolchains...
●
Native: toolchain runs 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

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Application Binary Interface (ABI)
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Guarantees that the libraries exist on all compliant
machines
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Ensures the integrity of the interface

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Application Program Interface (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

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Application Program Interface (API)

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API & ABI

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Static & Dynamic Compiling

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Yocto
●
Tools and methods 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)

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Other Programming Languages
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C++/Qt
●
Python
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Golang
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Node.js
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Lua
●
Scratch
●
Java ...

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Refrences