> > And for the buffer: %*phN is difficult to read IMO. What about %*ph? Or
> > %*phD at least?
> 
> My problem with that is that it increases the length of the output by 50% and
> there's a hard limit on how much output we may produce.

Is it PAGE_SIZE? How is this handled when the buffer is so big that the
limit will be reached anyhow? Note that it is really uncommon to
transfer kilobytes in one go via i2c. Usually, big transfers are split
up into smaller fragments, say 128-256 byte. So, for readability, I'd
still favour %*ph.