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totalnoob
Joined: 22 Oct 2006
Posts: 24
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| Converting ADC Result to output as Voltage on LCD |
 Posted: Tue Nov 21, 2006 1:14 pm |
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Ok I'm reading in an analog voltage from 0 to 5V into the ANO pin of a 16F877A. I'm trying to convert that value into it's corresponding voltage so that I can display it on an i2c LCD. I get the LCD to read out the string "Voltage: " but then after that where I tell it to display the numbers it only displays 0.00 to 0.02. All that changes is the last bit going between 0 and 2.
Here's the code I'm using, the main program is pretty simple but the LCD.h file I wrote is where the problem is. The function at the very end is the function that I'm having trouble with. I appreciate any comments or suggestions as to what I'm doing wrong.
Main code:
| Code: | #include <16F877A.h>
#device ADC=8
#include <string.h>
#include <LCD.h>
#use delay(clock=20000000)
#fuses HS,BROWNOUT,PUT,NOLVP
//set up i2c peripheral and use hardware SSP
#use i2c(Master,sda=PIN_C4,scl=PIN_C3,FORCE_HW)
#BYTE ADCON0=0x85
unsigned char buffer1[20];
unsigned char error;
void main()
{
setup_adc(ADC_CLOCK_DIV_32);
setup_adc_ports(ALL_ANALOG);
while(1)
{
delay_ms(50);
set_adc_channel(0);
error=read_adc();
set_pos(1);
strcpy(buffer1,"Voltage: ");
LCD_write(buffer1);
LCD_write_V(error);
ADCON0 |= 0x04;
}
} |
LCD.h file
| Code: | #include <string.h>
#include <STDLIB.H>
#use delay(clock=20000000)
#use i2c(Master,sda=PIN_C4,scl=PIN_C3,FORCE_HW)
#define lcd_addr 0xC6 //LCD Address
unsigned char i,max,voltage;
unsigned char buffer[20];
unsigned char pos,num,var,digit1,digit2,digit3,tens,ones,dec,j;
unsigned long int sca_res;
/***********************************************************************************************
Function to Initialize LCD Screen
***********************************************************************************************/
void init_LCD(void)
{
i2c_start(); //set i2c to start condition
i2c_write(lcd_addr); //send lcd address
i2c_write(0x00); //write to register 0
i2c_write(0x05); //cursor type: underline
i2c_write(0x0C); //clears screen and sets cursor to home position
i2c_stop();
}
/***********************************************************************************************
Function to write a string to the LCD
***********************************************************************************************/
void LCD_write(text)
{
i2c_start();
i2c_write(lcd_addr);
max=strlen(text);
for(j=0; j<=max; j++)
{
i2c_write(text[j-1]);
}
i2c_stop();
}
/***********************************************************************************************
Function to find the ascii equivalent of a 3 digit decimal number
***********************************************************************************************/
void getnum(num)
{
digit1=0;
for(i=1;i<10;i++)
{ if(num>=100)
{ digit1=digit1+1;
num=num-100; } }
tens=digit1+48;
digit2=0;
for(i=1;i<10;i++)
{ if(num>=10)
{ digit2=digit2+1;
num=num-10; } }
ones=digit2+48;
digit3=0;
for(i=1;i<10;i++)
{ if(num>=1)
{ digit3=digit3+1;
num=num-1; } }
dec=digit3+48;
}
/***********************************************************************************************
Function to write the result of getnum() to the LCD
***********************************************************************************************/
void LCD_write_num(val)
{
i2c_start();
i2c_write(lcd_addr);
getnum(val);
if(tens==48)
{
i2c_write(32);
i2c_write(ones);
//i2c_write(0x2E);
i2c_write(dec);
}
else
{
i2c_write(tens);
i2c_write(ones);
//i2c_write(0x2E);
i2c_write(dec);
}
i2c_stop();
}
/***********************************************************************************************
Function to set cursor position on LCD screen
***********************************************************************************************/
void set_pos(pos)
{
delay_ms(1);
i2c_start();
i2c_write(lcd_addr);
i2c_write(0x02);
i2c_write(pos);
i2c_stop();
}
/***********************************************************************************************
***********************************************************************************************/
void LCD_write_V(unsigned char a2d_res)
{
i2c_start();
i2c_write(lcd_addr);
sca_res=a2d_res*196;
voltage=sca_res/100;
getnum(voltage);
i2c_write(tens);
i2c_write(0x2E);
i2c_write(ones);
i2c_write(dec);
i2c_stop();
} |
I changed the code to add i2c_stop() at the end of all my functions in the LCD.h file and got rid of the stop in my while loop. Amazingly I got it all worked out to where it does what it did before. So I'm still having the problem with the voltage conversion not displaying properly. I appreciate the input because I'm stumped.
Last edited by totalnoob on Tue Nov 21, 2006 3:12 pm; edited 2 times in total |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Tue Nov 21, 2006 1:23 pm |
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When you posted your code, you didn't disable HTML, so your code
got messed up. For example, I'm sure you don't want this:
To fix this problem, edit your post. Delete all the code that you posted.
Do a fresh copy and paste of the correct code into your post, but this
time, select the box below the posting window to disable HTML.
It looks like this:
| Quote: | | x Disable HTML in this post |
Also, I notice you didn't do some of the things I suggested in my
last reply (in a previous thread). You still have all your i2c routines
ending without an i2c_stop() statement. This is totally against
standard coding practice. Look at all i2c routines in this forum and
in the CCS drivers library. All routines end with i2c_stop(). Instead,
you have stuck one i2c_stop() in main(). You need to fix this. |
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PCM programmer
Joined: 06 Sep 2003
Posts: 21708
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| Posted: Tue Nov 21, 2006 4:46 pm |
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Here's a quick modification of your LCD_write_V() routine.
This uses sprintf() to handle the conversion to an ASCII string.
Substitute this routine for your own, and see if it starts working.
| Code: |
void LCD_write_V(unsigned char a2d_res)
{
char buffer[5];
float voltage;
voltage = ((float)a2d_res * 1.96)/100.0;
sprintf(buffer, "%1.2f", voltage);
i2c_start();
i2c_write(lcd_addr);
i2c_write(buffer[0]);
i2c_write(buffer[1]);
i2c_write(buffer[2]);
i2c_write(buffer[3]);
i2c_stop();
} |
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totalnoob
Joined: 22 Oct 2006
Posts: 24
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| Posted: Tue Nov 21, 2006 6:15 pm |
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You may not have all the answers but so far you've had all of mine!! 
It's working great now. Thank you once again for the excellent help. |
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