In the job search for embedded development, solid foundational knowledge is the key to success.
1. Program Compilation and Execution Process
Four Stages of Generating Executable Programs
Preprocessing → Compilation → Assembly → Linking
- Preprocessing Stage: Handles macro definitions, header file inclusions, conditional compilation, and other pre-compilation directives.
- Compilation Stage: Converts the preprocessed code into assembly code.
- Assembly Stage: Converts assembly code into machine code, generating object files.
- Linking Stage: Links multiple object files and library files into the final executable program.
This process reflects the complete conversion path from high-level language to machine language, and understanding the responsibilities of each stage is crucial for debugging and optimization.
2. In-Depth Analysis of Communication Protocols
SPI Communication Protocol
SPI (Serial Peripheral Interface) is a high-speed, full-duplex synchronous serial communication protocol.
Core Configuration Parameters:
- CPOL (Clock Polarity): Defines the level state of the clock signal when idle.
- CPHA (Clock Phase): Defines the clock edge on which data is sampled.
| CPOL | CPHA | Working Mode Description |
|---|---|---|
| 0 | 0 | Idle state is low, data is sampled on the rising edge. |
| 0 | 1 | Idle state is low, data is sampled on the falling edge. |
| 1 | 0 | Idle state is high, data is sampled on the falling edge. |
| 1 | 1 | Idle state is high, data is sampled on the rising edge. |
Advantages of SPI over I2C:
- Higher Speed: SPI can reach tens of MHz, while I2C is limited to 400 KHz.
- Full-Duplex Communication: Can send and receive data simultaneously, resulting in higher efficiency.
- Flexible Transmission: Data frame length is not limited to 8 bits.
- Simplified Protocol: No start and stop signals, making control logic simpler.
Important Detail: The SPI bus uses a MSB first transmission method, meaning the most significant bit is sent first.
Key Points of the I2C Protocol
The Necessity of Pull-Up Resistors:
- Ensures the bus remains high when idle.
- Completes level conversion with open-drain outputs.
Advantages of Open-Drain Outputs:
- Prevents output level conflicts between different devices that could damage components.
- Achieves a logical