Q: What is the best way to manage read-only root filesystems on embedded Linux? Answer Read-only rootfs is essential for embedded systems reliability and security. Implement overlayfs on top of a read-only squashfs root: mount overlayfs with upperdir on tmpfs/ramfs…
Q: How to implement secure OTA firmware updates on embedded Linux devices? Answer Secure OTA on embedded Linux: (1) Use A/B partition scheme – write to inactive partition verify then switch boot. (2) Authenticate with asymmetric signature: sign firmware with…
Q: How to configure and debug the Linux network stack for real-time Ethernet applications? Answer For real-time Ethernet (IEEE 1588 PTP TSN): configure the network stack with proper socket buffers (net.core.rmem_max) and interrupt coalescing (ethtool -C). Use XDP (eXpress Data…
Q: How to write a Linux kernel device driver for custom hardware (I2C/SPI/GPIO)? Answer For I2C/SPI kernel drivers: use the Linux kernel subsystem APIs. I2C: implement struct i2c_device_id table and probe()/remove() functions using i2c_master_send()/i2c_master_recv(). SPI: use struct spi_device with spi_write_then_read()…
Q: What are the key differences between Buildroot Yocto and OpenWrt for embedded Linux? Answer Buildroot: builds from scratch simple Makefile-based fast to set up produces minimal images. Best for: single-product devices quick prototype limited team. Cons: no package management…
Q: How to reduce Linux kernel boot time from seconds to milliseconds? Answer Standard Linux boot on embedded systems takes 3-30 seconds. Optimizations: (1) Remove unnecessary kernel drivers. (2) Use U-Boot Falcon Mode to boot directly to the application without…
Q: How to design PCB for IPC-A-610 Class 3 high-reliability electronics? Answer IPC-A-610 Class 3 (High Performance Electronic Products) requires tighter tolerances than Class 2: (1) Minimum annular ring: 0.05 mm vs 0.025 mm for Class 2. (2) Solder joint…
Q: What is the correct approach for PCB schematic capture and symbol/footprint libraries? Answer Schematic best practices: hierarchical design with modular blocks. Each sheet should have a clear title block with version number and date. Use net labels instead of…
Q: How to route USB 2.0 differential pairs on PCB with proper impedance control? Answer USB 2.0 (480 Mbps): route D+ and D- as a differential pair with 90 Ohm +-15% differential impedance. Keep intra-pair length match 3 mm. Route…
Q: What are the manufacturing design rules (DFM) that every PCB designer must follow? Answer Essential DFM rules: (1) Minimum trace width/spacing: 0.1 mm (4 mil) standard; 0.15 mm (6 mil) recommended for yield. (2) Minimum drill: 0.2 mm (8…