Re: Translating an embedded C algorithm

[Niklas Holsti <niklas.holsti@nospam.please>]

Ludovic Brenta wrote:
> Niklas Holsti writes:
> [...]
> 
> Hi Niklas,
> 
> I think your program is excellent.  You are the first who used a fixed
> point real type and never to return an "invalid" temperature; both
> were the Right Thing to Do, IMHO.

Thanks.

>  Would you like to work in avionics? :)

I used to work on space SW (www.ssf.fi). I quit partly (but not mainly) 
because the customers started to specify C as the implementation 
language "for reasons of business strategy" or some such phrase.

>>The function to convert ADC counts to temperatures then seems suitable
>>for a child of package ADC.
> 
> 
> It does not need to be a child of ADC; it could be another top-level
> package.

True. Firstly, I wanted to demonstrate child packages; secondly, the 
conversion is very dependent on the type ADC.Count_T (its nature and 
range), so a child package feels natural to me.

>  Better yet, reverse the relationship to hide the ADC in a
> private child package:
> 
> package Thermometer is
>    function Temperature return Temperatures.Reading_T;
>    function Temperature return Temperatures.Celsius_T;
>    Out_Of_Range : exception;
> end Thermometer;

I agree "in the large" that those SW parts that need to know the 
temperature should be able to get it from a top-level package like that, 
without knowing that the temperature (in this version of the 
application) is acquired through the ADC. My code focuses on the issues 
of "programming in the small".

> private package Thermometer.Some_Particular_Kind_Of_Sensor is
>    type Count_T is range 0 .. 1024;
>    ...
> end Thermometer.Some_Particular_Kind_Of_Sensor;

I assumed that the ADC would be used to read various voltages, not just 
thermometer voltages. All these ADC channels share the same type Count_T 
(defined by the nature of the ADC itself), so its definition should not 
depend on the Sensor that is being read, which is why I defined Count_T 
in the package ADC.

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
       .      @       .