Displaying 7bit signed value

[jackchaos]

I'm using MIOS_AIN_Pin7bitGet() to get an unsigned 7 bit value (0-127) from my pots.

Some of the pots need to handle parameters as signed values -63 to +63 where center is 0.

I'm able to transmit the correct values over MIDI by:

parameter += 0x40;

parameter &= 0x7f;

However, I'm having trouble displaying the values correctly on the LCD.

Positive values are showing up fine, but as I turn into the negative range, the value is displayed as if it were unsigned (because 'parameter' is unsigned).

How can I display an unsigned char as a signed 7bit value?

Also, the MIOS_LCD_PrintBCD2 functions are not printing leading zeros eg " 6" instead of "06".

Can anyone suggest a straight forward way of printing the zero?

Regards

Edited November 9, 2009 by jackchaos

[TK.]

; --------------------------------------------------------------------------

;; print dec value -64..63

CS_MENU_PRINT_PMDec7

        movwf   TMP1

        movlw   ' '             ; space or "-"?

        btfss   TMP1, 6; (if value <= 0x3f (6th bit cleared), print "-"

        movlw '-'

        call   MIOS_LCD_PrintChar


CS_MENU_PRINT_PMDec7_WO_Sign

        movf    TMP1, W         ; calc: 0x40-value

        sublw   0x40

        btfsc   WREG, 7                 ; negate value if negative to get absolute value

        negf    WREG, ACCESS

        goto    MIOS_LCD_PrintBCD2      ; and print it

[/code]






The same in C:

[code]

  if( value < 64 ) {

    MIOS_LCD_PrintChar('-');

    MIOS_LCD_PrintBCD2(64-value);

  } else {

    MIOS_LCD_PrintChar(' ');

    MIOS_LCD_PrintBCD2(value-64);

  }

The same for MIOS32:

  MIOS32_LCD_PrintFormattedString("%3d", (int)value - 64);

[/code]








[code]

; --------------------------------------------------------------------------

;; print dec value patted with 0

CS_MENU_PRINT_Dec000

        clrf    MIOS_PARAMETER1

        call    MIOS_HLP_Dec2BCD

        movf    MIOS_PARAMETER2, W

        call    MIOS_LCD_PrintHex1

        movf    MIOS_PARAMETER1, W

        goto    MIOS_LCD_PrintHex2

The same in C:

  MIOS_HLP_Dec2BCD(value);

  MIOS_LCD_PrintHex1(MIOS_PARAMETER2); 

  MIOS_LCD_PrintHex2(MIOS_PARAMETER1); 

[/code]




The same for MIOS32:

[code]

  MIOS32_LCD_PrintFormattedString("%03d", value);

Best Regards, Thorsten.

[TK.]

P.S.: I added the MIOS32 variant...

[jackchaos]

Thorsten

The first example is easily understood and will work perfect for me.

I'm a bit lost on the second example, but I'll take your word for it. I'll try it tonite when I get home.

Thanks

[TK.]

I'm a bit lost on the second example, but I'll take your word for it. I'll try it tonite when I get home.

The details are explained here:

http://www.ucapps.de/cmios8_fun.html#MIOS_HLP_Dec2BCD

MIOS_LCD_BCD* uses MIOS_HLP_Dec2BCD internally, and removes the leading zeroes by spaces.

If you want to output leading zeroes, just print the original BCD code (binary coded digits, each digit is coded in 4 bits) with MIOS_LCD_PrintHex2 (to print the rightmost binary coded digits) resp. MIOS_LCD_PrintHex1 (to print a single (the leftmost) binary digit)

I changed the C example code (removed the bitshifting), so that it matches with the example given in the documentation.

Best Regards, Thorsten.