Peripheral Interfacing and Hardware Abstraction Questions

Basic understanding of common peripherals: ADC (Analog-to-Digital Converter), DAC (Digital-to-Analog Converter), timers, PWM (Pulse-Width Modulation), UART, SPI, I2C, GPIO. Knowledge of how to interface with these peripherals using registers or hardware abstraction layers. Understanding of communication protocols at a basic level.

MediumTechnical

75 practiced

Describe and provide pseudocode in C for configuring an SPI master peripheral to perform a full-duplex DMA transfer of N bytes (simultaneous TX and RX). Explain necessary DMA channel setups for TX and RX, which DMA/channel triggers to start first, how to synchronize completion, how to handle mismatched buffer sizes, and what cache maintenance is required if the MCU has a data cache.

MediumTechnical

91 practiced

Explain safe methods to protect shared data accessed by both ISRs and foreground (main) code in a bare-metal embedded system. Cover disabling/enabling interrupts, using atomic operations if supported, critical sections, using lock-free FIFOs/ring buffers, and considerations around nested interrupts and priority masking (e.g., NVIC/BASEPRI on Cortex-M). Provide short pseudocode for protecting a 32-bit counter updated in both contexts.

HardTechnical

72 practiced

You observe intermittent CRC errors on high-speed SPI transfers between an MCU and an external ADC. Provide a structured debugging approach: what electrical measurements to take (oscilloscope traces, eye diagrams), what firmware checks to perform (verify CPOL/CPHA, CS timing, DMA alignment), what hardware mitigations to try (series termination, drive strength, proper routing/grounding), and how to assess sources like jitter, crosstalk, or clock domain issues. Propose both quick mitigations and long-term fixes.

MediumTechnical

96 practiced

Implement in C an interrupt-safe circular (ring) buffer to receive UART bytes in a bare-metal environment. Requirements: fixed buffer size (no dynamic allocation), O(1) push/pop, safe concurrent access where ISR is producer and main context is consumer (no mutexes), and a reliable way to distinguish empty vs full. Provide the buffer struct and push/pop functions and explain volatile and memory-order considerations.

EasyTechnical

68 practiced

Explain hardware timers and counters in microcontrollers: common timer modes (up, down, up/down), prescalers, auto-reload/period registers, capture/compare channels, overflow/underflow interrupts, and typical uses such as event timing, input capture, PWM, and scheduling. Discuss how prescalers affect resolution and maximum measurable interval.

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