Searching \ for 'Multiplexing and 7 seg LEDs' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/displays.htm?key=leds
Search entire site for: 'Multiplexing and 7 seg LEDs'.

Truncated match.
PICList Thread
'Multiplexing and 7 seg LEDs'
1999\03\04@050659 by Brian Jones

flavicon
face
Folks
        a couple of days ago there was a thread re multiplexing 7
seg leds from 16F84. Has anyone considered the M5450 LED
drivers. Serial in (only 2 PIC pins!!!) and 34 parallel out. Designed
specifically for driving 4*7 seg LEDs but output can sink 15mW so
might be useful as a general port expander. Will run at clock
speeds up to 0.5Mhz which should be OK for many applications.
Looks simple to program, clock start bit, 4*8 data bits (7 seg +dp),
2 extra bits (for centre colon on clock displays). 36th clock high
loads the shift registers into their latches, next clock low generates
reset.

Farnell (at least) stock them.

Farnell and Radio Spares also stock complete 4* 7 seg LED
modules from Three Five systems that have the drivers built in.

Haven't tried this yet but hope to get chance this w'end.

Brian
Brian E Jones
Centre for Java Technology
IBM HURSLEY

1999\03\04@201136 by Russell McMahon

picon face
I have used the 5450 - it is as easy to use as it seems.
The only gotcha's are ensuring the correct number of clock pulses per
cycle so it doesn't get lost.
Driving from PICBASIC (!) takes only a few lines of code.
Display brightness controllable. No segment resistors needed. Very
few other parts needed  - a few r's and c's.
Good drive current (15ma? per pin) (sink only).
An oldie but a goodie.


Russell McMahon


From: Brian Jones <spam_OUTbejonesTakeThisOuTspamHURSLEY.IBM.COM>
        a couple of days ago there was a thread re multiplexing 7
seg leds from 16F84. Has anyone considered the M5450 LED
drivers. Serial in (only 2 PIC pins!!!) and 34 parallel out. Designed
specifically for driving 4*7 seg LEDs but output can sink 15mW so
might be useful as a general port expander. Will run at clock
speeds up to 0.5Mhz which should be OK for many applications.
Looks simple to program, clock start bit, 4*8 data bits (7 seg +dp),
2 extra bits (for centre colon on clock displays). 36th clock high
loads the shift registers into their latches, next clock low
generates
reset.

1999\03\05@172019 by Gerhard Fiedler

picon face
At 09:38 03/05/99 +1300, Russell McMahon wrote:
>I have used the 5450 - it is as easy to use as it seems.
>The only gotcha's are ensuring the correct number of clock pulses per
>cycle so it doesn't get lost.

is there a way to set it into a defined state if it gets lost?

ge

1999\03\06@013604 by Russell McMahon

picon face
The book suggests yes but I recall having some problems with this
early on (some years ago).
(Something like sending a single data bit followed by more than a
complete set of clock bits. The IC starts the frame at the first data
bit and then clocks through one frame and stops until another clocked
in high is received. I don't know if my original problems were my
programming or a failure of the IC to match claimed specs (the former
seems more likely :-)).

In practice it seems very well behaved when driven as intended.



Russell McMahon
.



From: Gerhard Fiedler <.....listsKILLspamspam@spam@HOME.COM>
>>I have used the 5450 - it is as easy to use as it seems.
>>The only gotcha's are ensuring the correct number of clock pulses
per
>>cycle so it doesn't get lost.
>
>is there a way to set it into a defined state if it gets lost?
>
>ge
>

1999\03\09@101555 by Holger Morgen

flavicon
face
Hi -

I have (tried the Farnell thing). It works like a charm - Also on the
smaller '508.

Holger

{Quote hidden}

More... (looser matching)
- Last day of these posts
- In 1999 , 2000 only
- Today
- New search...