Link to Chinese Version.
In embedded system development, the host computer refers to the device that interacts with the slave computer, typically acting as the controller.
In this project, the host computer uses a Raspberry Pi 5, and the salve computer is an Arduino Uno, connected via USB.
Code Design
The workflow of the host computer can be simplified as: responding to salve computer requests.
- Reply with connection confirmation when receiving ping command
- Send instructions from the command queue when receiving WaitCommand
- Requeue instructions when receiving execution failure reports
stateDiagram
[*] --> WaitForRequest
WaitForRequest --> HandlePing : Receive ping command
HandlePing --> WaitForRequest : Send connection response
WaitForRequest --> HandleWaitCommand : Receive WaitCommand
HandleWaitCommand --> WaitForRequest : Send next instruction
WaitForRequest --> HandleFailure : Receive failure report
HandleFailure --> WaitForRequest : Requeue instruction
state HandlePing {
Send_connection_response
}
state HandleWaitCommand {
Check_command_queue
Send_next_instruction
}
state HandleFailure {
Log_error
Rollback_command_to_queue
}
Additionally, to package the host computer as an SDK, we configured pyproject.toml for easy distribution as a Python module.
Issues & Solutions
Parameter Parsing Exception
Analysis: salve computer packets only use first 8 bytes as valid data, causing parsing issues in Python’s strong typing system which requires handling all 16 bytes.
Solution: Modify salve computer to write zeros in unused bytes.
Serial Port Not Found
Analysis: Development environment used Linux (Raspberry Pi OS) via VS Code Remote, while debugging used Windows (laptop).
Solution: Add serial port parameter configuration in test code.
Testing
Created test programs in /test directory that:
- Prompt for serial port address
- Create command queue using Python built-in list
- Pass queue and port address to communication function
- Run as separate thread
- Enter main loop accepting servo rotation degree inputs
host and salve computer testing is synchronized. Refer to the salve computer development blog for more details.
Below is a screenshot from testing video:
