Embedded Hardware Interfaces
Embedded hardware interfaces are the wiring-level protocols, such as GPIO, UART, I2C, SPI, and CAN, that a microcontroller uses to talk to sensors, displays, and other chips on the same circuit board.
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Intro
Embedded Hardware Interfaces
What they are
Embedded hardware interfaces are the wired protocols a microcontroller or system-on-chip uses to talk to the other chips sitting on the same board: a temperature sensor, a display, a memory chip, a motor driver. Each interface defines the physical wiring, the electrical signaling, and the rules for exchanging bits over those wires. Six interfaces cover almost everything you'll encounter: GPIO, UART, I2C, SPI, PWM, and the analog-to-digital converter (ADC). A seventh, CAN, shows up specifically when many nodes share one bus, as in a car or an industrial machine.
These are short-distance, board-level connections, typically centimeters of trace or a short cable, not the wireless or networked links that carry data off the board entirely.
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Sources
- https://www.nxp.com/docs/en/user-guide/UM10204.pdf
Supports
- SDA/SCL two-wire bus, open-drain signaling requiring pull-up resistors
- 7-bit and 10-bit device addressing
- Standard-mode (100 kbit/s), Fast-mode (400 kbit/s), Fast-mode Plus (1 Mbit/s), High-speed mode (3.4 Mbit/s), and unidirectional Ultra Fast-mode (5 Mbit/s)
- Quiz answers on pull-up purpose and speed-mode ordering
- https://docs.kernel.org/driver-api/spi.html
Supports
- SPI as a synchronous four-wire link (SCK, MOSI, MISO, chip-select) with no formal standards body
- Host/target (master/slave) roles and full-duplex operation
- Absence of device addressing; one chip-select line required per device
- CPOL/CPHA clock polarity and phase defining SPI's four clock modes
- Typical SPI use cases: sensors, memory, displays, ADC/DAC, SD/MMC cards, BIOS flash
- Typical SPI clock speed (~10 MHz) cited in the cheatsheet
- Quiz answers on SPI wiring cost and clock-mode mismatch
- https://docs.arduino.cc/learn/communication/uart/
Supports
- UART as asynchronous, point-to-point serial communication over TX/RX with no shared clock line
- Byte framing: start bit, data bits, optional parity bit, stop bit(s)
- Requirement that both ends agree on baud rate in advance
- Typical UART use cases: debugging, logging, connecting peripheral modules
- Quiz answer on why baud rate must be pre-agreed
- https://docs.kernel.org/driver-api/gpio/intro.html
Supports
- Definition of GPIO as a flexible, software-controlled digital signal
- GPIO use cases: driving indicators, reading switches, bit-banging serial protocols
- Open-drain/open-source signaling concept and its role in shared-bus protocols like I2C
- Quiz answers on GPIO's basic function and the bit-banging technique
- https://docs.kernel.org/userspace-api/gpio/chardev.html
Supports
- GPIO character device model (/dev/gpiochipN, line offsets)
- Line request/read/write operations underlying gpiodetect, gpioinfo, gpioget, gpioset
- Practice-reference GPIO command usage
- https://docs.kernel.org/i2c/dev-interface.html
Supports
- I2C userspace device file naming (/dev/i2c-N)
- i2c-tools utilities (i2cdetect, i2cget, i2cset, i2cdump) and their purposes
- I2C_SLAVE ioctl addressing (7-bit vs. 10-bit)
- Practice-reference I2C command usage
- https://docs.kernel.org/driver-api/pwm.html
Supports
- PWM defined by period and duty cycle
- Typical PWM use cases: LED dimming, fan speed control, haptic feedback
- Quiz answer on what duty cycle controls
- https://docs.espressif.com/projects/arduino-esp32/en/latest/api/adc.html
Supports
- ADC definition and purpose (converting analog voltage to digital form)
- Resolution in bits and corresponding output value ranges (e.g., 12-bit default, 0-4095)
- Attenuation settings extending measurable input voltage range
- Distinction between raw and calibrated (millivolt) readings
- Quiz answer on ADC resolution vs. measurable range
- https://docs.arduino.cc/language-reference/en/functions/analog-io/analogRead/
Supports
- analogRead() returning a value proportional to input voltage
- Classic AVR-based Arduino ADC resolution (10-bit, 0-1023 range)
- Quiz answer on ADC resolution vs. measurable range
- https://www.tekeye.uk/downloads/can2spec.pdf
Supports
- CAN differential signaling (CAN_H/CAN_L)
- Multi-master bus architecture
- Non-destructive arbitration by dominant/recessive bits, lowest identifier wins
- Standard (11-bit) vs. extended (29-bit) frame identifiers (CAN 2.0A/2.0B)
- Classic CAN maximum bit rate of 1 Mbit/s, cited in the cheatsheet
- Quiz answers on CAN arbitration and identifier priority
- https://www.raspberrypi.com/documentation/computers/raspberry-pi.html
Supports
- 40-pin GPIO header present on standard Raspberry Pi boards
- 3.3V GPIO I/O level
- I2C, SPI, and UART listed among the board's hardware communication interfaces