PICMicrocontollerInput / OutputLEDMethods

Driving an LED bargraph display

From Regulus Berdin

Given a number in bin, from 1 to 30, this code will drive that number of LED's on.

```; 1-30 to 30 leds
;input:   bin
;output:  led1,led2,led3,led4

convert:
clrf    led1
clrf    led2
clrf    led3
clrf    led4
incf    bin,f
loop:
decfsz  bin,f           ;do not include 0
goto   \$+2
return

decf    bin,f
setc                    ;turn on led
rlf     led4,f
rlf     led3,f
rlf     led2,f
rlf     led1,f
goto    loop

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

I have another solution, using the fact that 1-30 bar is equal to 2^y -
1.  This routine is isochronous and faster on some values than the
above.

Here goes:

convert:
clrf    a1
clrf    a2
clrf    a3
clrf    a4

movlw   a4              ;2^bin
btfsc   bin,3
movlw  a3
btfsc   bin,4
addlw  -2               ;corrected from 'movlw  a1'
movwf   FSR

movlw   B'00000001'
btfsc   bin,1
movlw  B'00000100'
movwf   INDF

btfsc   bin,0

btfsc   bin,2
swapf  INDF,f

movlw   1               ;subtract by 1
subwf   a4,f
skpc
subwf  a3,f
skpc
subwf  a2,f
skpc
subwf  a1,f

```

You don't need a 30bit number just because you want to drive a 30led bar :)  All you need is a number from 0 to 30, which boils down to a simple division, if your representation is linear. 0->0%->no led, 65535->100%->all (30) leds. that's 30 intervals for 65535, hence each interval (corresponding to one led more) is 65535/30... you divide your load by this number, and get the number of leds to switch on.

```
```

 file: /Techref/microchip/ledbargraph.htm, 2KB, , updated: 2009/2/13 16:22, local time: 2024/4/22 06:25, TOP NEW HELP FIND:  3.238.117.130:LOG IN

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