=20
Hi Byron,

Thanks, I guess I should have gone and read that datasheet. I just =
assumed
you meant a BCD to 7 Seg display driver. I understand now what you =
meant.

I'll add the driver chip and implement the algorithm you suggested and =
come
back if I have more questions :-).

> Your algorithm is slightly more complex now. Also to prevent bleed =
some
rearranging is in order:
>=20
>  0) Turn off all displays. Prevents bleed.
>  1) Set the correct segment for display X by incrementing segment =
count
(SC) on
>     7445 DCBA input. I'd normally use a shadow register for this but =
I'm
>     paranoid.
>  2) Check to see if the segment is supposed to be on.
>  3) If it's supposed to be on, then turn on the display
>  4) If SC > 7 then SC =3D 0 and X =3D X+1
>  4) If (X > 4), set X =3D 1 [You can also do this by shifing a 0 =
through
>     the 4 bits assigned to the BC557.
>=20
> Clock speed should be fine. Note that you should delay for each =
segment
whether or not it is turned on or off.


  _____ =20

Andr=E9 Miller =09


-----Original Message-----
From: pic microcontroller discussion list =
[mailto:PICLIST@MITVMA.MIT.EDU] On
Behalf Of Byron A Jeff
Sent: 17 March 2004 11:46 PM
To: PICLIST@MITVMA.MIT.EDU
Subject: Re: [PIC:] Multiplexing seven segment displays, correct =
resistor
values?


> One question though (I guess I can just go read this in the 7445=20
> Datasheet!) the driver presumably has a fixed number of 'shapes' it=20
> can display, say, 0-9, a-f. I wouldn't be able to make custom shapes,=20
> or use it to drive the decimal point, right?

You missed the point a bit. The 7445 is a 1 of 10 BCD decoder. So you =
put in
a 4 bit BCD number from 0-9 and the part drives one (and only one) of 10
outputs low with up to 80 ma of sink current.



BAJ

--
http://www.piclist.com hint: PICList Posts must start with ONE topic:
[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads