Help to convert common cathod to common anode seven segment display...

[manoj soorya]

Hello Everybody

I have a code for a calculator with common cathod. How it convert common anode display that I can use?

This is the asm code.


Any help would be appriciated.

Thank you

 

[be80be]

Where you see these change to 1 to 0 and the 0 to 1.

          ADDWF       PCL,F

            RETLW       B'01111111'

            RETLW       B'10111111'

            RETLW       B'11011111'

            RETLW       B'11101111'

            RETLW       B'11110111'

            RETLW       B'11111011'

            RETLW       B'11111101'

            RETLW       B'11111110'

            MOVLW       B'11111111'

So this become this

RETLW      B'01111111'    like this for each B'10000000'

But for all them where ever they are in the code just change the state from a 1 to a 0
and change the 0 to and 1.

 

[manoj soorya]

Is it will work as common Anode display?

 

[be80be]

It should the way it is it goes high you change the code to go low and wire it up right it should work.

 

[Ian Rogers]

In asm add the line comf in the code

  CALL  TABLE   
  MOVWF  BUFER2  
  COMF BUFER2   ; flips the bits for common anode

 

[Les Jones]

Don't forget to invert the digit drive signals as well if it is a multiplexed display. If the cathodes are driven with NPN transistors with the emitters to ground then these will need to be changed to PNP transistors with the emitters connected to Vcc.

Les.

 

[manoj soorya]

In asm add the line comf in the code

  CALL  TABLE  
  MOVWF  BUFER2 
  COMF BUFER2   ; flips the bits for common anode

All segment are ON when run the hardware. need any change in hardware like invert the digit drive signals?

 

[manoj soorya]

Where you see these change to 1 to 0 and the 0 to 1.

          ADDWF       PCL,F

            RETLW       B'01111111'

            RETLW       B'10111111'

            RETLW       B'11011111'

            RETLW       B'11101111'

            RETLW       B'11110111'

            RETLW       B'11111011'

            RETLW       B'11111101'

            RETLW       B'11111110'

            MOVLW       B'11111111'

So this become this

RETLW      B'01111111'    like this for each B'10000000'

But for all them where ever they are in the code just change the state from a 1 to a 0
and change the 0 to and 1.

Its not working... All segment of the LED are ON...

 

[manoj soorya]

Any simple method just like...




CALL TABLE
MOVWF BUFER2
COMF BUFER2 ; flips the bits for common anode

 

[Ian Rogers]

You have to change the software... AND you need to flip the drive like Les said... Only both will make the common anode work..

 

[manoj soorya]

You have to change the software... AND you need to flip the drive like Les said... Only both will make the common anode work..

And any simple way to change in only software only??

 

[Ian Rogers]

If you have a circuit diagram, but the LED is different from the schematic, You'll have to wire it differently anyway..

 

[manoj soorya]

You have to change the software... AND you need to flip the drive like Les said... Only both will make the common anode work..

I just make these setup..only for one digit. But it is not working too.. Segment 'F' will Bright more and another segment are just bright.

This is the setup I made..

 

[manoj soorya]

If you have a circuit diagram, but the LED is different from the schematic, You'll have to wire it differently anyway..

I dont get you. Master

 

[manoj soorya]

In common cathod display, its is working good...
But in Common anode display, its a problem.

I use NPN and PNP as used to test. But the problem persisit...

I have much more Common Anode display, Less Common Cathode. and its multiplexed PCB too..

I dont have multiplexed Display PCB for common cathod.

Is really complecated to remove all common anode and changed to common cathod.

So that I need to work with Common anode display

 

[manoj soorya]

why they use common cathod display? is it simple to make the code?

 

[be80be]

Without see the sch you could maybe do this

 

[Ian Rogers]

If you have the display as your schematic, Then just using COMF will work... Unless the code isn't working??

 

[Les Jones]

You need to provide the ORIGINAL schematic of how it was designed for common cathode and ALSO how you have connected the common anode LEDs. You would not just decide to replace an NPN transistor with a PNP one just because you had one. (I hope.)

Les.

 

[manoj soorya]

You need to provide the ORIGINAL schematic of how it was designed for common cathode and ALSO how you have connected the common anode LEDs. You would not just decide to replace an NPN transistor with a PNP one just because you had one. (I hope.)

Les.

here is the schematic :