C for embedded controllers (was Re: Timed mechanical fuel injection )

[John S Gwynne]

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   In message <199511220503.XAA06506 at net.dris.com> , you write:
 
| going to market it.  It continually is improving, and I agree with Larry,
| use machine language.  Although something like C is easier to program,
| machine code is more direct to the point, requires less memory, and the
| hardware often can be made simpler.  My fuel injection system uses one HC11,

ok, I don't want to start a debate nor a flame war on this, but some of
the advantages of *not* using assembly should also be discussed
(again?).

| C is easier to program

Absolutely. From conception to the final debugged program, assembly
language takes me at least 4 times longer to develope for *small*
programs (YMMV, the ratio is worse for RISC). Once you get used to
using a high level debugger, like gdb, its very hard to revert back
(and unnecessary) to a low level monitor. RTOS, math libraries, and
other software tools are much more available for C (gnu bin-utilities,
gcc, gdb, newlib, glibc, RTEMS,... are examples currently ported to
efi332. Programming efi332 is *no* different than programming under any
unix system. I've often ran the same program on an SGI workstation,
linux PC, and efi332 *without* any modifications.).

| machine code is more direct to the point

I don't understand this comment... do not the two programs (C vs
assembly) do the same thing?

| requires less memory

True, but maybe only by 10-20% with a good optimizing C compiler (gcc
for the 68k is a good example. Optimization is cpu dependent.). With
larger programs it is conceivable the C will be smaller since it
generally promotes better structure. The archive has examples
comparing assembly to C for the 68000 (efi68k).

| hardware often can be made simpler

This is nonsense. Remember, assembly can easily be placed in-line
within any C code. Functionally there can be no difference.  Execution
maybe slightly slower for C in general, but time critical routines can
be written in assembly.


                                   John S Gwynne
                                          Gwynne.1 at osu.edu
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