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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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 Posted: Sat Nov 11, 2006 12:16 am |
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Use the sprintf() function to convert a number to an ASCII string
and put it in an array. Example:
The following program displays:
| Code: |
#include <16F877.H>
#fuses XT, NOWDT, NOPROTECT, BROWNOUT, PUT, NOLVP
#use delay(clock=4000000)
#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)
//============================
void main()
{
float value = 4.940000;
char array[20];
sprintf(array, "%3.2f", value);
printf(array);
while(1);
} |
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Ttelmah
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| Posted: Sat Nov 11, 2006 4:56 am |
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As a few other comments:
You are reading the ADC twice. Why?.
value=read_adc();
Performs a start, waits for the conversion, and then reads it. The next pair of lines, basically do the same again....
Your printf format is faulty, which is probably why it does not work. In printf, the first number, is the _total field width_ (not the digits in front of the DP). Then the number after the DP, is how many trailing digits are required. Most C's, are smart enough, that if the first number is smaller than the second, they increase the first. CCS does not. You need to make the field big enough to hold the whole result.
Also, remember that on the ADC, the 'full' voltage on the Vref, is actually one count _above_ the maximum value read. So you wuld need to use /0x400, not 0x3FF, to get correct scaling.
Then, consider not using a float. Floating point arithmetic, is slow. You don't actually need a float to do what you want. If you only want 2DP, depending on the accuracy you really 'need', you might consider:
| Code: |
int32 value;
value=read_adc();
value*=247L;
value/=512;
printf("%4.2w",value);
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This generates in integer arithmetic, adc*247/512, which is then displayed as x.xx. In int32, this can be made really accurate, and is a lot quicker than float (especially if the division is a binary value, which is then done by simple rotation).
Best Wishes |
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new2ccs
Joined: 29 Oct 2006
Posts: 10
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| printf to an array |
| Posted: Sun Nov 12, 2006 10:57 am |
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Hello PCM PROGRAMMER and Ttelmah,
thank you for your responses, but i used both of your code and it did not work for me. Some how generating a value and assign it to an array does not work. It only works when i assign it directly ex: char array[] ={'12','a'};. something like this.
Ttelmah, I used your int32 stuff to replace the float and it gave me the wrong result of the voltage conversion.
so i guess i have to figure out a way to format it myself instead of using the built in function then.
thank you very much guys. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Sun Nov 12, 2006 3:54 pm |
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| Quote: |
I am using PCH 3.163 and MPLAB 7.31 to debug(ICD2)
I used both of your code and it did not work for me.
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I tested the program that I posted above with PCM vs. 3.163.
I used an ICD2 to program it into an 16F877 on a PicDem2-Plus board.
It worked OK. It displayed this in the terminal window:
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new2ccs
Joined: 29 Oct 2006
Posts: 10
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| Posted: Mon Nov 13, 2006 10:12 am |
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| sorry, it is my display function that has problems, but i don't know why. I can display everything else ok, but when i used my display_volts function then my lcd won't work. With the code that you showed me, it worked i know now cuz when debugging if i hit the run button then i couldn't see anything, but when i stop it, then i sometimes see my NUMBERS. |
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Ttelmah
Guest
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| Posted: Mon Nov 13, 2006 10:22 am |
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You did read the bit about using sprintf, not printf?. Printf, outputs to the currently selected output device. It does not return anything, so the contents of 'answer', will always be garbage.
I think 3.193, may be too old for the %w format to work properly. However you can simulate this by just sprintf ing the value to a string, and adding the decimal point yourself.
Best Wishes |
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new2ccs
Joined: 29 Oct 2006
Posts: 10
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| Posted: Mon Nov 13, 2006 11:14 am |
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with the code that PCM PROGRAMMER showed me. it works ok.(sprintf). all i need to do now is to figure out why when using display_volts function with the array size of less than 16 characters , it messes up my lcd display(won't work).
| Code: | char text1[]= {' ',' ','B','u','z','z','e','r',
' ','=',' ','S','3',' ',' ',' '}; |
this function is to display data to LCD.
| Code: | void display(char arr[])
{
int i;
for(i = 0; i < 16; i++)
{
if( arr[i] == '\0') // for different arr sizes (check for NULL
i = 16;
else
lcd_write_data(1,arr[i]);
}
} |
so in my MAIN function i do this
display_volts(value). this function then calls the display function
above to display my voltage array that is created my the sprintf(arr,"%3.2f, value); |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Mon Nov 13, 2006 11:59 am |
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Here's a demo program for the PicDem2-Plus that works.
Use the "Flex_lcd.c" driver that you can get from here. It's already
configured to work with a PicDem2-Plus.
http://www.ccsinfo.com/forum/viewtopic.php?t=24661
This program reads the value of the trimpot, converts it to volts,
and displays it on the LCD on the PicDem2-Plus board. I tested
this with PCM vs. 3.249 and it works OK.
I also installed your version, 3.163, and it works with that one too.
For your version, the "AN0" constant doesn't exist. Use the RA0_ANALOG
constant instead. (They're the same thing).
Change this line
| Code: | | setup_adc_ports(AN0); |
to this:
| Code: | | setup_adc_ports(RA0_ANALOG); |
Then it will compile with vs. 3.163.
| Code: |
#include <16F877.H>
#device adc=10
#fuses XT, NOWDT, NOPROTECT, BROWNOUT, PUT, NOLVP
#use delay(clock=4000000)
//#use rs232(baud=9600, xmit=PIN_C6, rcv=PIN_C7, ERRORS)
#include "flex_lcd.c"
//============================
void main()
{
int16 adc_value;
float volts;
lcd_init();
setup_adc_ports(AN0);
setup_adc(ADC_CLOCK_DIV_8);
set_adc_channel(0);
while(1)
{
adc_value = read_adc();
volts = (float)(adc_value * 5)/1023.0;
printf(lcd_putc, "\f%3.2f", volts);
delay_ms(500);
}
} |
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Ttelmah
Guest
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| Posted: Mon Nov 13, 2006 3:29 pm |
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The answer to the array size, is simple. A _string_, always needs one more character than the number in the text, for the '\0' terminator character.
Best Wishes |
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new2ccs
Joined: 29 Oct 2006
Posts: 10
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| Posted: Tue Nov 14, 2006 9:58 am |
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thanks for the code, but suddenly my program works now. Maybe I changed the line in my loop from i =16 after the if statement to BREAK;
| Code: | void display(char arr[])
{
int i;
for( i = 0; i <16; i++ )
{
if( arr[i] == '\0')
break;
else
lcd_write_data(1,arr[i]);
}
} |
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new2ccs
Joined: 29 Oct 2006
Posts: 10
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| address lines picdem 2+ |
| Posted: Wed Nov 15, 2006 3:39 pm |
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I have a question about the address lines of the LCD. In the data sheet of hd44780U says line 2 = 0x40 and line 1 = 0X00, but when debugging the flex.c code. i notice that line 1 = 0xff and line 2 =0xbf. Why not line 1 = 00 and line 2 =40.
HD44780U
00 01 02 03 04 05 06 07 08 09 0A 0B0C0D0E 27
40 41 42 43 44 45 46 47 48 49 4A 4B4C4D4E 4F |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Wed Nov 15, 2006 3:47 pm |
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| Quote: | | when debugging the flex.c code. i notice that line 1 = 0xff and line 2 =0xbf |
In the lcd_gotoxy() function, it sets the address to 0x00 for line 1
and to 0x40 for line 2. |
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