The Problem:
A forum member shared their set_gpio() function, which sets a single pin to a specific state (high or low). However, the function had a limitation: it unintentionally cleared all other DIO pins when setting the target pin. This caused issues when the user wanted to turn on an LED while manipulating other outputs, like relays.
The Solution:
Digilent Engineer Arthur responded with a helpful approach: reading the current state of all DIO pins, modifying the desired bit for the target LED, and then writing the entire modified state back out. This ensures only the target pin is affected.
- Read Current State: Before modifying anything, the code reads the current state of all DIO pins. This provides a “snapshot” of the current configuration.
- Modify LED Bit: The specific bit corresponding to the target LED (e.g., READY_LED) is identified. The code then modifies only this bit within the read state data, setting it to the desired value (high or low) for the LED.
- Write Back Modified State: Finally, the entire modified state, including unchanged bits for other pins, is written back to the DIO controller. This ensures only the target LED is affected while preserving the state of other pins.
Benefits:
This method offers several advantages:
- Clarity: It’s a clear and well-understood approach for manipulating individual bits.
- Efficiency: While potentially requiring more code than a single-line write function, it efficiently updates only the necessary bit.
- Flexibility: This approach is adaptable to various scenarios involving multiple digital outputs.
Conclusion:
This forum exchange highlights a common challenge in embedded systems programming and provides a practical solution using the WaveForms Python SDK. The approach of reading, modifying, and writing the entire DIO state ensures precise control over individual pins while maintaining the state of others. By understanding this technique, users can write more flexible and efficient code for their Digilent projects.
For a more detailed discussion and to see the full code examples, visit the thread on the Digilent forum: here. Feel free to ask any follow-up questions you may have in the forum thread, where our community of engineers and users can assist you!
