Serial Communication

The purpose of serial communication is to transfer information between devices while using fewer wires than parallel communication.

Light(AM and FM)
Ti Calculators
USB Serial Protocol
UART
I2C
Can Bus

Terms

Synchronous - Uses a clock signal to
- Asynchronous - Doesn’t have a clock signal and relies on a predetermined time for each bit(baud rate). -
- precise timing and eliminating the need for start/stop bits. This allows for faster and more efficient data transfer compared to asynchronous communication. It’s commonly used in
Synchronous(Uses clock) vs Asynchronous
Half duplex - Only one device can send/receive data at a time.
Differential
- Instead of using 0v and +V which can get corrupted with noise, you use -V and +V usually wrapped around each other, thus canceling any noise.
  - The difference between -V and +V is a 1 or 0.
CRC and error correction
- Cyclic Redundancy Check
Here are some common variables used to understand serial communication protocols:

Synchronous vs. Asynchronous – Synchronous uses a clock signal; asynchronous does not. Half-Duplex vs. Full-Duplex – Half-duplex allows one device to send/receive at a time, while full-duplex allows both simultaneously. Differential Signaling – Uses -V and +V instead of 0V and +V to reduce noise interference. Baud Rate – The speed of data transmission, measured in bits per second (bps). CRC and Error Correction – Cyclic Redundancy Check and other methods ensure data integrity.

You said: Are there more? ChatGPT said: Yes, here are additional key variables in serial communication protocols:

Bit Order (Endianness) – Determines whether the most significant bit (MSB) or least significant bit (LSB) is sent first. Parity Bit – Used for basic error detection (Even, Odd, None). Stop Bits – Define the end of a data packet (e.g., 1, 1.5, or 2 bits). Flow Control – Manages data flow to prevent buffer overflows (e.g., XON/XOFF for software, RTS/CTS for hardware). Framing – Defines how data is structured, including start bits, data length, parity, and stop bits. Voltage Levels – Specifies signal levels, such as RS-232 (±12V) vs. TTL (0V/5V). Protocol-Specific Features – Some protocols (e.g., SPI, I²C, CAN) include unique properties like multi-master support or address-based communication.

Other common ports

ADC - Analog to digital converter
DAC - Digital to analog converter
PWM - Pulse width modulation
Power
- AVDD - Analog Voltage Drain.

UART - Universal Asynchronous Receiver/Transmitter

Transmit at a baud rate/symbols per second(usually bits per second)
USART adds a clock line to allow for synchronous communication.
Ports
- TX - Transmit
- RX - Receive
- GND - Ground
- RTS(Optional) - Request to send. Transmitting device requests to send data.
- DTR(Optional) - Data Terminal Ready. Transmitting device tells receiving device that it’s powered and ready to communicate.
- CTS(Optional) - Clear to send. Receiving device says to the transmitting device that it’s clear to send data.

SPI - Serial Peripheral Interface

Ports
- CS - Chip select
- SCK - Serial clock signal
- MOSI - Master out slave in. Master pin is TX.
- MISO - Master in slave out. Master pin is RX.
QSPI - Quad SPI. 2 MOSI and MISO.

I2C - Inter Integrated Circuit

Ports
- SCL - Serial clock line
- SDA - Serial data line
- GND - Ground

CAN - Controller area network

Multiple devices connected together
- All devices can send and receive data
- Each device connects to the H and L lines.
  - Send ID then message
  - Only the device with the ID reads the message
Half duplex - Only one device can send/receive data at a time.
Asynchronous
Ports
- CANH - CAN High
- CANL - CAN Low
- Uses a CN transceiver(like TJA1040) to convert between TD/RD to CANH and CANL
  - TD - Transmit data.
  - RD - Receive data.
Data package
- Start bit
- ID bits/Arbitration field
- Control bit
- Data
- CRC bits
- End frame bits