Koenraad Lelong wrote:
Hi,
I'm porting a driver, originally written in C, for an LCD to be used
with an embedded arm-processor (STM32).
The original driver uses SPI, my driver will use a USART in synchronous
mode because the STM32 has no SPI for 9-bit. Unfortunately, the
bit-order is reversed between SPI and USART transmission.
Does anyone knows an efficient way to reverse bit-order of a byte for
the arm-processor ? I'm going to look into the assembly language of the
arm-processor, but maybe someone knows this immediately.
For old processors like 8085 or Z80 I know how to do this, but
arm-assembler is new to me.
I think I'd use a lookup table (making sure it's cacheable),
particularly since what you're doing is going to be called frequently
and you're likely to have much more than 64K memory.
--
Mark Morgan Lloyd
markMLl .AT. telemetry.co .DOT. uk
[Opinions above are the author's, not those of his employers or colleagues]
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