Serial Communication Methods

Study Notes

Serial Communication

Asynchronous serial transmission: sender does not share a clock signal with the receiver, and both agree on timing parameters in advance.
Synchronous serial transmission: sender and receiver share a common clock signal, ensuring more efficient transmission.

Serial-to-Parallel and Parallel-to-Serial Conversion

Serial communication involves transmitting data over a single wire, converting parallel data to serial format.
Clock signal is sent with serial data in synchronous communication systems.

ASCII Encoding

ASCII (American Standard Code for Information Interchange) encodes 128 characters, including 95 printable characters and 33 non-printing control characters.
ASCII characters can be represented by 7 bits, commonly stored as one byte for storage convenience.

UTF-8 Encoding

UTF-8 (UCS Transformation Format—8-bit) is a variable-width encoding scheme derived from ASCII.
UTF-8 avoids endianness and byte order marks, making it widely used for the World Wide Web.

MBED UART API

The mbed API provides functions to access the UART peripheral, including:
- Creating a Serial port with specified transmit and receive pins.
- Setting the baud rate and transmission format.
- Determining if a character is available to read or write.
- Attaching a function to call whenever a serial interrupt is generated.

Simple Example: send periodic message to PC

Uses the mbed UART API to send a periodic message to the PC via UART.

Mbed UART Sample Program

Defines two serial connections: pc for printing debug messages and uart for UART communication.
示例代码使用putc()和getc()函数来send和receive数据。

UART Example 2

Communicates with two separate devices having different UART baud rates.
Uses two Serial objects for UART communication and sets the baud rate accordingly.

Serial Peripheral Interface (SPI) Bus

SPI is a synchronous communication protocol requiring a clock wire.
SPI bus has four wires: SCLK, MOSI, MISO, and CS (chip select).
Devices communicate in master/slave mode, with the master initiating data transfers.

SPI Overview

SPI bus features:
- Synchronous communication.
- Four-wire serial bus.
- Devices communicate in master/slave mode.
- Multiple slaves are enabled individually by the select lines.

SPI Master and Slave

Master: initiates data transfers and asserts the CS line of the target peripheral.
Slave: responds to the master's data transfer requests.

SPI Port on STM32F411RET6

The SPI pins on the STM32F411RET6 are:
- SPI1: MOSI (PA7), MISO (PA6), SCK (PA5), and NSS/CS (PA4).
- SPI2: MOSI (PB15), MISO (PB14), SCK (PB13), and NSS/CS (PB12).
- SPI3: MOSI (PC12), MISO (PC11), SCK (PC10), and NSS/CS (PA15 or PA4).

SPI Modes: Clock Polarity and Clock Phase

SPI provides four communication modes based on Clock Polarity (CPOL) and Clock Phase (CPHA).
CPOL and CPHA can be specified as '0' or '1' to form four unique modes.

MBED SPI API

The mbed API provides functions to access the SPI peripheral, including:
- Creating a SPI master connected to the specified pins.
- Configuring the data transmission format.
- Setting the SPI bus clock frequency.
- Writing data to the SPI slave and returning the response.

Description

Test your understanding of serial communication methods, including asynchronous and synchronous serial transmission, and serial-to-parallel conversion. Learn about the advantages and disadvantages of each method and how they are used in data transmission.