Displaying 7bit signed value

MIOS programming (C)
1

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

2 
; --------------------------------------------------------------------------
;; 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.

3

P.S.: I added the MIOS32 variant…

4

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

5

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.