Thank you for valuable info. I think all of this (completed whit what is missing) can be part of Jallib and Jaluino documentation to avoid reinventing the wheel...
On Jul 28, 10:28 pm, vasile surducan <[email protected]> wrote: > On Wed, Jul 28, 2010 at 11:42 AM, vasi vasi <[email protected]> wrote: > > Hi Joep and Vasile, > > > This is the scrolling text: > > "HELLO JOEP And VASILE _ THIS USE Your LibrArY" > > >http://www.youtube.com/watch?v=RatJm6wGxpI > > Oh boy, you are a rested (hodinit) guy too...:) > > > > > I wanted to learn how to use 4 digits as a decent display and for this, I > > used also timer0_isr_interval.jal (to light another 8 LED's at different > > speed) because I don't know yet another method of "multitasking". > > I use FreeJALduino with EvB 4.3 version 4 board (with already bricked > > ATmega :( ) and entire assembly draws very much current, the onboard 5V > > regulator gets very very HOT. An external source of 5V is obligatory for > > this kind of application. > > Anyway, the conclusion is: It is too much trouble and too many pins > > allocated for this task. > > :) > search on the internet for "gugaplexing", "charlieplexing" and other > "plexing" methodes... > > > It require a separate microcontroller for this and in this case, you can > > transmit data on serial. For 4 digits and 8 LEDs I used all available pins > > on FreeJALduino and the DOT from digits remained unconnected. But the > > experience gained is invaluable. > > > The segments get lighted on 0 logic and also digit selection is made with 0 > > logic (I don't know how to draw a schematic for this). The LED's are lighted > > also on 0 logic (this is easy, but program inside is for 1 logic - I must > > negate the byte). In the movie, the digits are lighted one at the time, > > 350uS long each but I modified the program for 950uS each to get rid of that > > echo. If is useful, I think it can be easily modified for Jaluino. All > > required files attached. > > Vasi, this is calling "ghosting". I've written an article about this problem > but right now is in evaluation at the IEEE-Micro magazine, maybe they will > reject it too, so you'll see it on my blog.... (I really hope not). > In a few words: as you can see from your movie, even taking a photo or a > movie to a multiplexed display is a difficult task. Depending how display is > routed to the PIC IO, there will be a ghosting situation, except if using > standalone 7seg drivers between the PIC and display. > The reason is the variable voltage level on pins when they are used as input > (pseudo high impedance or highZ, PIC/Atmel does not have a true highZ output > circuit as old logic buffers have). A LED connected between two input pins > of a PIC will light, and this is ghosting caused by un-fixed voltage level > (if all highZ would have for example the theoretical VDD/2 voltage level > fixed -used in all drawings-, that would not happen). The second cause of a > ghosting is a bad timing multiplexing. Switch from one segment to another > using highZ (meaning input), switch from one anode(cathode) to another > anode(cathode) through an OFF state. > The time which one display lights gave the overall current drawn. A good > choice is 1mS to 3mS for standard display, less than 1mS for high efficiency > display. Between switching a shut OFF time of 50-100uS is reasonable. > > Vasile -- You received this message because you are subscribed to the Google Groups "jallib" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/jallib?hl=en.
