Thanks Byron, I read your other post, very informative! What I have done in the meantime is change the algorithm as you and = others have suggested to get rid of 'ghosting'. It actually helped quite a bit = to increase the contrast. I didn't even realise it was ghosting till I took = a closer look at the 'off' segments. Unfortunately I had already built a proto/dev board without the display driver. But if I were to build a new one I will definitely look into = using the method you suggested. Although I guess I could just put the driver between that board and my PIC. One question though (I guess I can just go read this in the 7445 = Datasheet!) the driver presumably has a fixed number of 'shapes' it can display, = say, 0-9, a-f. I wouldn't be able to make custom shapes, or use it to drive = the decimal point, right? _____ =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 10:10 PM To: PICLIST@MITVMA.MIT.EDU Subject: Re: [PIC:] Multiplexing seven segment displays, correct = resistor values? On Wed, Mar 17, 2004 at 03:28:11PM +0200, Andre Miller wrote: > I probably can, but doing it this way is more fun :-). > > I'm just going to lower the resistor values to get the correct=20 > brightness then (without exceeding the PIC ratings of course). See my other post. I don't think you'll get there. Presuming a 1.7V drop = the absolute lowest resistance is 3.3/.024 -> 137 ohms. And that's pushing = the edge of the PIC I/O current drive capability. But the brightness will = still only seem to 137*4 -> 548 ohms. So it won't seem too bright. My suggestion is to add a 7445 BCD to decimal driver will allow for 70 = ma sink through a 47 ohm resistor, though you can only light 1 segment at a time instead of one display at a time. BAJ. > > _____ > > Andr? Miller > > -----Original Message----- > From: pic microcontroller discussion list=20 > [mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of=20 > bertrand.rozier@PRAGMATEC.NET > Sent: 17 March 2004 02:41 PM > To: PICLIST@MITVMA.MIT.EDU > Subject: Re: [PIC:] Multiplexing seven segment displays, correct=20 > resistor values? > > Hi, > > I think there is not possiblity to improve that in soft. > Could you confirm that you can not add a 7-segment drivers? > > BR > Bertrand Rozier > www.pragmatec.net > PICOS18 Solutions > > Selon Andre Miller : > > > Hi, > > > > If I increase the 'on' time for a display, wont this then also=20 > > increase the 'off' time for the other displays, thereby negating the = > > benefit? I should be able to get this same effect by increasing the=20 > > prescaler on my timer interrupt that drives the displays. I tried=20 > > changing this and the lower frequency of updating didn't seem to=20 > > make a difference, except that it starts to flicker noticibly when=20 > > its too low > :-). > > > > _____ > > > > Andr? Miller > > > > > > -----Original Message----- > > From: pic microcontroller discussion list=20 > > [mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of Spehro Pefhany > > Sent: 17 March 2004 12:31 PM > > To: PICLIST@MITVMA.MIT.EDU > > Subject: Re: [PIC:] Multiplexing seven segment displays, correct=20 > > resistor values? > > > > At 08:12 PM 3/17/2004 +1000, you wrote: > > > > > If you have the time to spare, leave the leds on for a while, few = > > >mS, then switch to the next segment, and so on. > > > In other words, increase the "on" time compared to the off time. > > > Only works if your chip hasn't much else to do. > > > > He's using interrupts, so his program can walk and chew gum at the=20 > > same time, no problem. It shouldn't use more than a couple percent=20 > > of the processor throughput. > > > > Best regards, > > > > Spehro Pefhany --"it's the network..." "The Journey is = the > > reward" > > speff@interlog.com Info for manufacturers: > http://www.trexon.com > > Embedded software/hardware/analog Info for designers: > > http://www.speff.com > > > > -- > http://www.piclist.com hint: PICList Posts must start with ONE topic: > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads