Chapter 4

1. (c) – The start bit. It starts a UART frame and is not configurable while setting up a UART connection. See more here: https://www.analog.com/en/analog-dialogue/articles/uart-a-hardware-communication-protocol.html.
2. (d) – UART has two different lines for transmitting and receiving, while others use a single line for data. This is not true. SPI also has two different lines for sending and receiving data packets. See https://www.analog.com/en/analog-dialogue/articles/introduction-to-spi-interface.html.
3. (b) – They need the same number of pin connections. This is not true. I2S has a word select (WS) line, which doesn't exist in I2C communication. See more here: https://www.allaboutcircuits.com/technical-articles/introduction-to-the-i2s-interface/.
4. (a) – Modem sleep and light sleep. In these modes of operation, ESP32 preserves its RAM state. See more here: https://lastminuteengineers.com/esp32-sleep-modes-power-consumption/.
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