Learn vocabulary for embedded communication protocols: SPI, I2C, UART, CAN bus, peripheral addressing, and bus collision detection.
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In SPI communication, what are MOSI and MISO?
SPI uses four lines: SCLK (clock), MOSI (master-to-peripheral data), MISO (peripheral-to-master data), and CS/SS (chip select). The full-duplex nature means data flows in both directions simultaneously, making SPI faster than I2C but requiring more pins.
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What is the role of the SDA and SCL lines in I2C?
I2C uses just two wires: SDA for data and SCL for clock. Both are open-drain (open-collector), meaning any device on the bus can pull the line low. Pull-up resistors hold the lines high when idle. Multiple devices share the same two wires, addressed by unique 7-bit or 10-bit addresses.
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What is 'baud rate' in UART communication?
Baud rate defines the speed of the UART link — common values are 9600, 115200, and 921600 baud. Unlike SPI and I2C, UART is asynchronous (no shared clock), so both ends must independently configure the same baud rate, data bits, parity, and stop bits.
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What does 'the peripheral is not responding on I2C' typically indicate?
In I2C, every transaction begins with the master sending the peripheral's address. If no device ACKs, a logic analyser will show the address byte followed by a NACK (non-acknowledge). Systematic diagnosis: verify address (check datasheet for address pins), test pull-ups, confirm VCC to the peripheral, and check wiring continuity.
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What is a 'bus collision' in embedded communication protocols?
On shared-bus protocols like I2C and CAN, collision/arbitration is built into the protocol. In CAN, nodes monitor the bus while transmitting — if a node detects its dominant bit has been overridden, it loses arbitration and backs off. I2C multi-master configurations similarly detect lost arbitration and retry. Detection and handling vocabulary is important in multi-master embedded designs.