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Asked: 2026-06-17T09:37:12+00:00

I have a function which prepares a data buffer and then sends it via

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I have a function which prepares a data buffer and then sends it via an externally provided API function which looks like:

send(uint8_t* data_buf, uint32_t length)

In my particular case, my code is always sending exactly 8 bytes and the first 7 bytes are always the same (I can’t change this fact; it’s some sort of message header).

Because I am in an limited, embedded environment, I would like to optimize the size and performance of my code, or at least choose the best tradeoff of the two.

Currently, I see two options:

  1. Create a global array. Initialize the first 7 bytes one time and then
    just overwrite the last byte before sending the array.
  2. Create a local array, write all 8 bytes and then send it.

Are there any better solutions than the two mentioned above?

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1 Answer

  1. Editorial Team

    Even on an embedded system, you can count on having more than 8 bytes of cache. Hence performance really doesn’t matter. databuf[8] will be fully in cache in both cases. The code size for the first case might be smaller by 2-3 instructions.

    (There’s often another issue: code/flash size and RAM size are distinct constraints, when you can XIP).

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