January 2, 2024

Optimizing Code Size and Performance on the nRF52

When developing for constrained embedded systems like the nRF52, it is crucial to optimize code size and performance to ensure efficient resource utilization. In this blog post, we will explore various techniques and examples to achieve just that.

1. Disable Unused Features: The nRF52 comes with a rich set of peripherals and features, but not all of them may be required for your specific application. By disabling unused features, you can significantly reduce code size and improve performance. For instance, if you don’t need Bluetooth functionality, disabling it can save a substantial amount of both flash and RAM.

Here’s an example of disabling unused features:

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// Disable Bluetooth functionality
#define NRF_SDH_BLE_ENABLED 0

2. Optimize Memory Allocation: Careful management of memory allocation can lead to significant improvements in code size and performance. Use smaller data types when appropriate, and avoid unnecessary padding or alignment. Additionally, try to limit dynamic memory allocation and prefer static allocation whenever possible to reduce overhead.

Here’s an example of optimizing memory allocation:

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// Use uint8_t instead of uint32_t if possible
uint8_t myVariable;

// Align structures to minimize padding
#pragma pack(push, 1)
struct MyStruct {
    uint8_t foo;
    uint16_t bar;
};
#pragma pack(pop)

3. Use Inline Functions: Inlining functions can eliminate the overhead of function calls, especially for small and frequently used code snippets. By instructing the compiler to inline specific functions, you can reduce both code size and execution time. However, be mindful not to inline large or infrequently used functions to avoid bloating your code.

Here’s an example of using inline functions:

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// Inline small and frequently used functions
inline uint8_t add(uint8_t a, uint8_t b) {
    return a + b;
}

4. Optimize Loops and Conditionals: Loops and conditionals are prime candidates for optimization. Minimize loop iterations and simplify logical conditions wherever possible. Consider using bit manipulation instead of boolean conditions to improve performance. Additionally, prefer switch statements over multiple if-else conditions, as they can be more efficient in certain situations.

Here’s an example of optimizing loops and conditionals:

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// Use bit manipulation instead of boolean conditions
if (x & 0x01) {
    // Do something
}

// Replace multiple if-else with switch statement
switch (value) {
    case 1:
        // Case 1 logic
        break;
    case 2:
        // Case 2 logic
        break;
    default:
        // Default logic
        break;
}

5. Enable Compiler Optimization: Leveraging compiler optimization flags can help improve both code size and performance. Different optimization levels (e.g., -O1, -O2, -O3) offer varying degrees of optimization, but be aware that higher levels may increase compilation time. Experiment with different optimization levels to find the right balance for your application.

Here’s an example of enabling compiler optimization flags (using GCC):

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gcc -O2 main.c -o main

In conclusion, optimizing code size and performance on the nRF52 involves a combination of strategic decision-making, careful coding practices, and leveraging compiler capabilities. By following the techniques outlined in this blog post, you can maximize resource utilization and enhance the efficiency of your embedded system.

Do you have any other tips or techniques for optimizing code size and performance on the nRF52?

➡️ Set default terminal profile in VS Code

⬅️ Debugging techniques for nRF52 applications

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