Harold,

In your example if adc has 0-9  it will call DoSomething();  but what we 
really need
is to create spot if it get to  9-10 then DoSomething();

thank you very much for your help

Andre




Harold Hallikainen wrote:

>Sure, I think that would work. The else if would be faster, but with a
>small number of comparisons, the improved readability of leaving out the
>elses is probably worthwhile. If the ranges "run into each other", a quick
>assembly language technique is to add negative numbers, less negative to
>more negative, until the result is negative, then branch out of the
>checks. A similar technique here would be to use a series of if elses with
>only one check per test. For example:
>
> if(adc<10)
>    DoSomething();
>  else if (adc<20)
>    DoSomethingElse();
>  else if(adc<30)
>    DoAnotherSomethinElse();
>
>This results in only one compare per if and skips the compares after success.
>
>Harold
>
>
>
>  
>
>>Harold,
>>
>>thanks for your replay.
>>Your brought interesting point on ADC conversion.
>>suppose I am looking for 951  I better test for 949-953
>>
>>if ((adc_x>948)&&(adc_x<954))		// looking for 951
>>
>>do you think above example will work?
>>
>>thanks for your help
>>
>>Andre
>>
>>
>>
>>
>>Harold Hallikainen wrote:
>>
>>    
>>
>>>Without all the elses, the if's after the successful test will continue
>>>to
>>>run. That is, every test will be run every time. With the elses, tests
>>>after the success will be skipped. Another way to do this, which is, I
>>>believe, more readable, is to use the switch-case statement.
>>>
>>>I am surprised that you are testing for 10 specific ADC values. It is
>>>unlikey that successive ADC readings will land on exactly a particular
>>>number. More likely they will be one count higher or lower, perhaps more
>>>variation depending on circuit stability. Do yo want to test the ADC for
>>>a
>>>range of values? If so, the if, or if else if test seem to be he only way
>>>to go (or a very large switch-case statement or a large array where the
>>>ADC indexes into it).
>>>
>>>Harold
>>>
>>>
>>>
>>>
>>>      
>>>
>>>>Hi to all engineers,
>>>>
>>>>I am reading ADC to compare 10 different values  if they are matched
>>>>then each match
>>>>has it's own set value. my question is.
>>>>
>>>>1. what is the different between  if else if  for example
>>>>
>>>>   if (adc_x==1023)        // 5v         1023
>>>>           {
>>>>           xbyte_lsb=0xff ;
>>>>           xbyte_msb=0x01 ;
>>>>           }
>>>>           else if (adc_x==921)   // 4,5v       921
>>>>           {
>>>>           xbyte_lsb=0x9A ;
>>>>           xbyte_msb=0x01 ;
>>>>           }
>>>>
>>>>or  without else if
>>>>
>>>>   if (adc_x==1023)        // 5v         1023
>>>>           {
>>>>           xbyte_lsb=0xff ;
>>>>           xbyte_msb=0x01 ;
>>>>           }
>>>>           if (adc_x==921)   // 4,5v       921
>>>>           {
>>>>           xbyte_lsb=0x9A ;
>>>>           xbyte_msb=0x01 ;
>>>>           }
>>>>
>>>>I do not clearly understand what does "else if"  do?
>>>>
>>>>is there better way of testing ADC ?
>>>>
>>>>Any feedback will appreciate.
>>>>
>>>>Andre
>>>>--
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>>>>
>>>>
>>>>
>>>>        
>>>>
>>>
>>>
>>>      
>>>
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>>
>>    
>>
>
>
>  
>

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