Re: Translating an embedded C algorithm

["Talulah" <paul.hills@uk.landisgyr.com>]

Thanks everyone for your very valuable comments. I'm sorry that the C
code I provided had a few problems - I had taken it out of a previous
project of mine and edited it for a stand-alone function, but
overlooked the values of the constants, and the comment in the header
returning INVALID_TEMPERATURE (which was originally FFFF hex), and a
couple of other things.

To answer Jeffrey Carter's assertion that I am not qualified to write
this book, I can only answer that since the majority of embedded RT
projects ARE written in C, then the majority audience for the book will
be interested in seeing examples written in C. That is no reflection on
the "quality" of the language, but is just facing facts. Secondly, the
product that this code came from is a domestic electricity meter for
India, a market of 18 million devices per year. This is not a
safety-critical product at all, but one which in those volumes must be
designed for the lowest cost possible. Hence the use of 4 diodes as a
temperature sensor, and hence (this may get more argument) the use of C
rather than Ada. Crossing an 8k ROM boundary (the current code is just
over 32kbytes) adds 3 pence (UK) to the cost on this microcontroller
(Renesas H8/3827). Multiply that by 18 million and the resulting half
million UK pounds is the reason I program in C. Thirdly, I am
thick-skinned enough to brush off rudeness from newsgroup posters, it
is just a shame that you decided not to post any useful comments.

By asking you kind people for help in reproducing the example in Ada,
it hopefully will allow readers to see the advantages that Ada can give
them, and encourage them to research Ada as a possible language for
future products that would benefit from these advantages, but also to
understand the disadvantage of code size and speed (hard hat firmly in
place after that!).

I understand now that a direct translation of the code into Ada would
not be a good illustration of the Ada language, and that an example
which performed the same calcuation, but added the additional useful
features would better serve. I have been sent an example written by a
member of your newsgroup which does this, introducing better
protection. I will also write a section in the text describing why a
direct translation is a bad idea, and demonstrate how the extra
features have made the code much more reliable.

Finally, I regret adding the section reading the calibration factor
from EEPROM!!! This is irrelevant to what I am trying to do with this
example anyway (which is to see how a simple algorithm is implemented
in different languages), and I will remove it. It is in the original C
code on the electricity meter of course.

Thanks again for all this discussion, it is vey useful for me.
regards,
paul