Ok, but when I have an integer, I can not compute the digit=B4s after =
the
comma, because these digits are zero in an integer,or not?=20

-----Urspr=FCngliche Nachricht-----
Von: Mike Harrison [mailto:mike@WHITEWING.CO.UK]
Gesendet: Donnerstag, 8. Mai 2003 17:27
An: PICLIST@MITVMA.MIT.EDU
Betreff: Re: AW: AW: AW: [PIC]:Floating point


This is a VERY inefficient way of doing things.
Most microcontroller apps deal with values from ADCs and the like which =
have
nowhere near enough
dynamic  range to justify the huge code and RAM penalty of using =
floating
point.=20

Just becase there's a decimal point in the display does not mean you =
need to
use FP.=20
You need FIXED point, so all the maths can be done as simple integer
operations.=20

If you need precision, a 32 bit long, suitably scaled,  will generally =
have
more accuracy, and use a
lot less code than a float.

so instead of representing, say 4.15V, you store 415, and write your =
display
routine to simply
insert the decimal in the appropriate position.=20


On Thu, 8 May 2003 17:17:21 +0200, you wrote:

>I need a 'float' because I have to display a voltage for example of =
41.5V.
>
>The following part of my program show=B4s the A/D- conversion and the
>mathematic operations that I need (a voltage range  of 0-5V form the =
A/D-
>result is conform to voltage range of 0-50V)
>
>
>void ermittleDigitalenWert()
>{
>        digitalwert =3D 0;=20
>        digitaleAnzeige =3D 0;
>        spannungsZehner =3D 0;
>        spannungsEiner =3D 0;
>        spannungsKomma =3D 0;
>        stromZehner =3D 0;
>        stromEiner =3D 0;
>        stromKomma =3D 0;
>        anzeigeSpannung =3D 0;
>        anzeigeStrom =3D 0;
>=09
>        digitalwert =3D ADRESH;
>        digitalwert |=3D (digitalwert << 8);
>        digitalwert |=3D ADRESL;
>        digitaleAnzeige =3D (float)(digitalwert * 5 / 1023.0);  =09
>        ADRESH =3D 0;
>        ADRESL =3D 0;
>}
>
>
>void main(void)
>{
>        init();
>        InitLCD();
>=09
>        while(1)
>        {
>                if(anzeigeAD =3D=3D TRUE)
>                {
>                        /************************A/D- Wandlung auf =
Kanal
>0********************/
>                        /*********************Spannung der ersten
>Halbbruecke*****************/
>                        ADCON0 =3D 0b10000001;
>                        ADGO =3D 1;
>                        while(ADGO =3D=3D 1);
>                        ermittleDigitalenWert();
>
>                        spannung_HB1 =3D (digitaleAnzeige * 60.94) / =
6.04;
>                        DelayS(1);
>                =09
>                        /************************A/D- Wandlung auf =
Kanal
>1********************/
>                        /********************Spannung der zweiten
>Halbbruecke*****************/
>                        ADCON0 =3D 0b10001001;
>                        ADGO =3D 1;
>                        while(ADGO =3D=3D 1);
>                        ermittleDigitalenWert();
>                        spannung_HB2 =3D (digitaleAnzeige * 60.94) / =
6.04;
>                =09
>                        if(spannung_HB2 > spannung_HB1)
>                        {
>                                anzeigeSpannung =3D spannung_HB2 -
>spannung_HB1;
>                                spannungPositiv =3D FALSE;
>                        }
>                        else
>                        {=09
>                                anzeigeSpannung =3D spannung_HB1 -
>spannung_HB2;
>                                spannungPositiv =3D TRUE;
>                        }
>                        anzeigeSpannung =3D spannung_HB1;
>                        spannungsZehner =3D (unsigned =
char)(anzeigeSpannung /
>10);
>                        spannungsEiner =3D (unsigned =
char)(anzeigeSpannung -
>(spannungsZehner * 10));
>                        spannungsKomma =3D (unsigned =
char)((anzeigeSpannung -
>(spannungsZehner * 10)
>=09
>- spannungsEiner) * 10);
>        =09
>=09
>/****************************Spannungsanzeige*************************/=

>                        WriteInstrToLCD(Set_DDRAM_Address + 0x42);
>                        WriteCharToLCD(' ');
>                =09
>                        if(spannungPositiv =3D=3D TRUE)
>                        {
>                                WriteCharToLCD('+');
>                        }
>                        else
>                        {
>                                WriteCharToLCD('-');
>                        }
>
>                        WriteCharToLCD(0x30 + spannungsZehner);
>                        WriteCharToLCD(0x30 + spannungsEiner);
>                        WriteCharToLCD('.');
>                        WriteCharToLCD(0x30 + spannungsKomma);
>                        spannung_HB1 =3D 0;
>                        spannung_HB2 =3D 0;
>                        DelayS(1);
>                                        =09
>
>-----Urspr=FCngliche Nachricht-----
>Von: Rick Regan [mailto:rdrdr2k@YAHOO.COM]
>Gesendet: Donnerstag, 8. Mai 2003 17:09
>An: PICLIST@MITVMA.MIT.EDU
>Betreff: Re: AW: AW: [PIC]:Floating point
>
>
>> No, that4s not the problem.....after the A/D-
>> conversion I make a type cast
>> from "integer" to "float". And if I try to show at
>> first the value of the
>> variable "voltage_HB1" on the display and then the
>> value of "voltage_HB2",
>> then I get the right values for both A/D- channels.
>
>Since A/D results are integer, could you explain
>why you need to make them 'float' to compare
>and display them?
>
>
>__________________________________
>Do you Yahoo!?
>The New Yahoo! Search - Faster. Easier. Bingo.
>http://search.yahoo.com
>
>--
>http://www.piclist.com hint: The list server can filter out subtopics
>(like ads or off topics) for you. See http://www.piclist.com/#topics

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics