Question

I m working on a project implementing a clock using PIC18, LCD, ... etc and I am using mikroC to implement this project.

However, I am not good at C and I am stuck at certain point. The clock has a menu with several options that will enable the user to set time, alarms, alarm sound, etc. The menu has the following:

1. Set Time
2. Add Alarm
3. Select Alarm
4. Add New Tone
5. Select Tone
6. EXIT

The clock has 3 pushbuttons, OK,RIGHT, and LEFT. When the clock power-on, it will show Set Time on LCD as default. I want to add a feature that when I press RIGHT pushbutton it should show Add Alarm but gradually not directly. I have 6 items in the menu so I have to do this gradually movement 12 times (6 for right and 6 for left). I have tried this as follows:

 Lcd_Out(2, 2, "   set Time   ");
 Delay_ms(50);
 Lcd_Out(2, 2, "  set Time    ");
 Delay_ms(50);
 Lcd_Out(2, 2, " set Time     ");
 Delay_ms(50);
 Lcd_Out(2, 2, " et Time      ");
 Delay_ms(50);
 Lcd_Out(2, 2, " t Time       ");
 Delay_ms(50);
 Lcd_Out(2, 2, " Time         ");
 Delay_ms(50);
 Lcd_Out(2, 2, " ime          ");
 Delay_ms(50);
 Lcd_Out(2, 2, " me           ");
 Delay_ms(50);
 Lcd_Out(2, 2, " e            ");
 Delay_ms(50);
 Lcd_Out(2, 2, "              ");
 Delay_ms(50);
 Lcd_Out(2, 2, "              ");
 Delay_ms(50);
 Lcd_Out(2, 2, "              ");
 Delay_ms(50);
 Lcd_Out(2, 2, "              ");
 Delay_ms(50);
 Lcd_Out(2, 2, "            A ");
 Delay_ms(50);
 Lcd_Out(2, 2, "           Ad ");
 Delay_ms(50);
 Lcd_Out(2, 2, "          Add ");
 Delay_ms(50);
 Lcd_Out(2, 2, "         Add  ");
 Delay_ms(50);
 Lcd_Out(2, 2, "        Add A ");
 Delay_ms(50);
 Lcd_Out(2, 2, "       Add Al ");
 Delay_ms(50);
 Lcd_Out(2, 2, "      Add Ala ");
 Delay_ms(50);
 Lcd_Out(2, 2, "     Add Alar ");
 Delay_ms(50);
 Lcd_Out(2, 2, "    Add Alarm ");
 Delay_ms(50);
 Lcd_Out(2, 2, "   Add Alarm  ");
 Delay_ms(50);
 Lcd_Out(2, 2, "  Add Alarm   ");

This was one movement and to do the others I need large code while the RAM of the PIC is limited. So, Can you guys help me solving this issue?

Answer 1

Here a variation avoiding all the memcpy, str*cpy orgy.

#define STRSZ 14

char str[STRZ*2+1] = "   set Time     Add Alarm   ";  /* The buffer must be writable */

for (i = 0; i <= STR_SZ; i++) {            // Loop
  char save_ch = str[i + STRZ];            // Save the character at the end 
  str[i + STRZ] = 0;                       // Terminate the string
  Lcd_Out (2, 2, str + i);                 
  str[i + STRZ] = save_ch;                 // Restore buffer
  Delay_ms (50);
}

EDIT: shift to right

for (i = STR_SZ; i >= 0; i--) {            // Loop
  char save_ch = str[i + STRZ];            // Save the character at the end 
  str[i + STRZ] = 0;                       // Terminate the string
  Lcd_Out (2, 2, str + i);                 
  str[i + STRZ] = save_ch;                 // Restore buffer
  Delay_ms (50);
}

On very small devices, avoiding unnecessary memory moves can be crucial

Answer 2

You need something like this:

#define STRSZ 14
//           <------------><------------>
char *str = "   set Time     Add Alarm   ";    // Two 14-char strings.
char disp[STRSZ+1];                            // Buffer for holding display string.
for (i = 0; i <= STR_SZ; i++) {                // Starting character to use.
    memcpy (disp, &(str[i]), STR_SZ);          // Copy the relevant bit.
    disp[STR_SZ] =   ;                       // And null-terminate.
    Lcd_Out (2, 2, disp);                      // Display it then wait.
    Delay_ms (50);
}

For shifting the other way, simply use:

for (i = STR_SZ; i >= 0; i--) {
    // blah blah blah
}

If you re looking for a more complete example, try:

#define STR_SZ 14
// PreCond: from and to MUST be 14-character strings. EXACTLY!
// Pass in from and to strings and 1 to go left, 0 to go right.

void transition (char *from, char *to, int goLeft) {
    // Space for transition and display strings.
    char str[STR_SZ * 2 + 1];
    char disp[STR_SZ + 1];

    // Transition variables.
    int pos, start, end, incr;

    // Check preconditions.
    if (strlen (from) != STR_SZ) return;
    if (strlen (to) != STR_SZ) return;

    // Different values for each direction.
    if (goLeft) {
        start = 0; end = STR_SZ + 1; incr = 1;
        strcpy (str, from); strcat (str, to);
    } else {
        start = STR_SZ; end = -1; incr = -1;
        strcpy (str, to); strcat (str, from);
    }

    // Do the transitions.
    for (pos = start; pos != end; pos += incr) {
        // Copy string portion to display then delay.
        memcpy (disp, &(str[i]), STR_SZ);
        disp[STR_SZ] =   ;
        Lcd_Out (2, 2, disp);
        Delay_ms (50);
    }
}

It s untested (other than in my head, which is usually pretty good) so you should consider it a starting point.

Answer 3

Most LCDs themselves support scrolling. So C libraries for LCDs provide functions for scrolling data. I have used PIC18 C library and it provides two functions

void lcd_scroll_left(char n) scrolls LCD screen left n positions.

void lcd_scroll_right(char n) scrolls LCD screen right n positions.

You can consult the documentation of the library that you are using for finding the function names you gotta use.

Microchip PIC18 C library for LCDs

友情链接