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hansknec
Joined: 30 Sep 2004
Posts: 25
Location: Virginia, USA
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| Bargraph Code for Hitachi type LCD |
 Posted: Thu Sep 30, 2004 1:02 pm |
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Does anybody have a function written to generate a horizontal bargraph on an LCD (with Hitachi HD44780 controller)? I have recently started using PIC C and also use PIC Basic Pro. In PBP I have an "include" file that writes straight bars to the CGRAM area of the display. Later if I wish to make a variable display as a bargraph I simply call a subroutine that automatically writes the bars and fill spaces to form the bar. In the code I have, each character space can contain 0 to 3 vertical lines, therefore a 16 character width display can have a bar that displays from 0 to 48 individual lines. I think I'll be able to convert the Basic to C, but a few of the LCD calls appear to be quite different in C. The basic bargraph code was written by Scott Edwards and released to the PIC basic users. I suppose I could post it if someone thinks they can properly modify it for C. I use 16X2 line parallel (4bit mode) lcd's exclusively, so please don't respond with serial LCD info unless it is somehow directly applicable.
-John |
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Will Reeve
Joined: 30 Oct 2003
Posts: 209
Location: Norfolk, England
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| Posted: Thu Sep 30, 2004 1:33 pm |
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I have done just what you suggest; the code was used on a VFD using a LCD ‘compatible’ controller. The VFD has the desired custom characters already in its character map. I see that the normal HD44780U LCD character map doesn’t have them so you will need to make your own custom characters.
You need 5, the first one has a single vertical line, the second 2, and so on until you have a completely solid character.
Basically the code works out how many solid characters to display, and then what the last character should be. Looking at it now it generates a 10 character bar graph in a string called bar as I was also giving a description of the variable graphed on the same line. You will have to modify the math to give you 16 characters!
Works very well in practice.
| Code: | /*******************************************************************************
* void generatebar(int8 percent)
* Purpose: This function generates the text line for the bar graph indicator
*/
void generate_bar(int8 percent) {
int8 solid,last;
int8 i = 0;
solid = percent / 10; // number of solid characters to display
last = percent - (solid * 10); // work out the last character
last /= 2;
if (solid) {
for (i=0;i<solid;i++)
bar[i] = 0x14;
} // if (solid)
if (last) {
last--;
bar[i] = 0x10 + last; // select last character
i++;
}
bar[i] = '\0';
} // generate_bar(int8 percent) |
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hansknec
Joined: 30 Sep 2004
Posts: 25
Location: Virginia, USA
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| Posted: Thu Sep 30, 2004 2:00 pm |
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Yes, this portion of the code looks straight forward, but it is the actual LCD writing that worries me. When writing to the CGRAM, it looks like I need to have the address and desired value to that address. When wanting the LCD to print a character, either from it's stock list of characters or the CGRAM, I simply enter the address of the character to print. With PBP it seemed easy, but I'm not sure when and where I should be using lcd_putc( char c) or lcd_send_byte(0,1) or the other multitude of commands available to me in C. I'm only in my 3rd day of actually writing to an LCD, so please forgive my ignorance. I know this can't be too hard. I need to tell it where to write and what to write. More code please if you have it.  |
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Will Reeve
Joined: 30 Oct 2003
Posts: 209
Location: Norfolk, England
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| Posted: Thu Sep 30, 2004 2:37 pm |
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Hi, I’ve dug some code out of an old project. This function will set up you user defined characters:
| Code: | /*****************************************************************************
* init_user_chars
* Purpose: Set pointer in LCD memory to CGRAM and load first 8 bytes with
* user defined characters. Reset pointer to line 1, position 1
*/
void init_user_chars(void) {
// User defined characters 5 x 7 but remember the cursor on 8
int8 i;
// char 0x00 nice degree sign
const char user_char[49] = {0x06, 0x09, 0x09, 0x06, 0x00, 0x00, 0x00, 0x00,
// char 0x01 nice tick sign
0x00, 0x00, 0x00, 0x01, 0x02, 0x14, 0x08, 0x00,
// char 0x02 approx sign
0x00, 0x00, 0x08, 0x1D, 0x17, 0x02, 0x00, 0x00,
// char 0x03 stir forward
0x00, 0x10, 0x08, 0x04, 0x02, 0x01, 0x00, 0x00,
// char 0x04 stir vertical
0x00, 0x04, 0x04, 0x04, 0x04, 0x04, 0x00, 0x00,
// char 0x05 stir backward
0x00, 0x01, 0x02, 0x04, 0x08, 0x10, 0x00, 0x00};
lcd_send_byte(0,64); // Sets ram address
for (i=0; i<49;i++)
lcd_send_byte(1,user_char[i]);
lcd_gotoxy(1,1); // Resets address to top line / position 1
} // init_user_chars |
This is the function I always use to write out data to the LCD.
| Code: | /*******************************************************************************
* send_to_lcd(int8 location,char *s1)
* Purpose: Write the supplied strings to the top or bottom line of the LCD
* 16x2 LCD screen depending on location
*/
void send_to_lcd(int8 location,char *s1) {
int i, iLen;
iLen=strlen(s1);
// Write to top line
lcd_gotoxy(1,location);
// Protect against coding errors
if (iLen>16)
iLen=16;
for(i=0;i<iLen;i++) {
// Built in auto substitution of Numerical zero with O
if(s1[i]==48) s1[i]=0x4F;
lcd_putc(s1[i]);
} // for
for (i=iLen; i<16; i++) lcd_putc(' ');
} // send_to_lcd |
| Code: | void lcd_putc(char c) {
lcd_send_byte(1,c);
} // lcd_putc |
This is a typical line of code which uses the send_to_lcd function.
| Code: | sprintf(line1,"Low Batteries");
send_to_lcd(1,line1); |
To send the user characters just send 0x00 to 0x05 for instance.
Hope these help. |
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