Q: What is the difference between MQTT MQTT-SN and CoAP protocols for IoT? Answer MQTT (MQ Telemetry Transport): TCP-based pub/sub protocol. Excellent for reliable always-connected devices. Overhead ~2 bytes header. Best for: gateways cloud-connected sensors. QoS 0 (at most once)…
Q: How to measure and optimize embedded Linux power consumption? Answer Power measurement: use a precision shunt resistor (1-10 mOhm) + oscilloscope with current probe or a bench power supply with current measurement. Software tools: powertop shows per-process power draw.…
Q: What are the security hardening steps for production embedded Linux devices? Answer Hardening steps: (1) Disable unused services (systemctl disable ). (2) Use AppArmor or SELinux to confine applications. (3) Remove SUID binaries where unnecessary. (4) Enable ASLR: CONFIG_ARCH_HAS_RANDOMIZE_BASE=y.…
Q: How to cross-compile Linux applications and kernel for embedded ARM targets? Answer Use a cross-compiler: for ARM64 (aarch64): aarch64-linux-gnu-gcc; for ARM32 (armv7): arm-linux-gnueabihf-gcc. Set CROSS_COMPILE=… and ARCH=arm64 in make commands. Build kernel: make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- defconfig then make ARCH=arm64…
Q: How to implement persistent storage with overlayroot and UBIFS on NAND flash? Answer For NAND-based systems (IoT gateways industrial controllers): use UBIFS on top of UBI (Unsorted Block Images) for wear-leveling and bad block management. Create: ubiattach /dev/ubi_ctrl -m…
Q: How to use Device Tree (DTS) overlays for configuring hardware on embedded Linux? Answer Device Tree overlays (.dtbo) dynamically modify the base .dtb to enable/configure hardware without rebuilding the kernel. Create overlay: write a .dts with a fragment@0 {…
Q: How to boot embedded Linux over the network (NFS root) for development? Answer Network boot eliminates flash writes during development. Configure U-Boot: setenv ipaddr setenv serverip setenv bootargs root=/dev/nfs nfsroot=:/path/to/rootfs rw ip=dhcp. On the host: install nfs-kernel-server export the…
Q: How to implement real-time constraints on embedded Linux with PREEMPT_RT? Answer The PREEMPT_RT patch makes the Linux kernel fully preemptible reducing worst-case interrupt latency from >100 us to
Q: How to configure and use GPIO interrupts in embedded Linux userspace? Answer Userspace GPIO access via libgpiod (Linux 4.8+): use gpiochip device files in Command-line: gpioset gpiochip0 23=1 to set gpioget gpiochip0 23 to read. For interrupts use…
Q: How to reduce embedded Linux memory footprint from hundreds of MB to OpenRC or runit. (3) Strip binaries with strip –strip-unneeded. (4) Use static linking for simple utilities. (5) Disable glibc locales (locales-all is huge). (6) Compile with -Os…