Comments on: Multiplexed Seven Segment Displays – Part II

By: Greg

Greg — Wed, 11 Jan 2012 08:21:05 +0000

On the ATmega328P, you want to set TCCR0B for the Prescaler on Timer0.

By: Robert

Robert — Fri, 02 Dec 2011 04:52:11 +0000

@Kolawole Hi, to answer some of your questions…
1) the resistors are current limiting resistors not pull ups.
2) not sure haven’t used CodeVision or STK500.
3) have you read the comments in ISR routine?

By: Kolawole Oladapo

Kolawole Oladapo — Thu, 01 Dec 2011 22:37:51 +0000

Hi Avinash

i am thinking of implementing this segmented display in a project in class i am using ATMega16 on an STK500 board. My questions are two fold
1. Would i still need the resistors shown in the schematic for PORTD and B knowing that these ports on the STK500 usually have pull up resistors associated with them.
2. I need an idea of what peripherals to configure since am using the Code Vision AVR C Compiler software.
3. Could you explain the fucntion of the wait loop and the timer 0 interrupt.

Thank you
Kola

By: Avinash

Avinash — Wed, 30 Nov 2011 03:35:03 +0000

@Willian,

The problem is simple enough to be recognized withing seconds! The thing is slowed down by a factor of 16.

In tutorial it is clearly written that the code is wriiten for a AVR running at 16Mhz. Have you set this frequency in Proteus ???

Have you set the fuse bytes to enable external crystal ?

Why don’t you built the circuit by following 100% of the steps as told in the tutorial ?

Why you are simulating it at all ??? Simulation is required during the development of the firmware. When you are getting 100% per-developed and tested code then whats the need of simulation ?(Thats too without setting of the Proteus properly). In this case you are debugging Proteus using the firmware (the exact opposite of what its meant for). Now you have found a bug in your proteus setup (instead of the firmware) so go correct it. Bye

By: William

William — Tue, 29 Nov 2011 22:31:42 +0000

I’m using Proteus to simulate your Stopwatch circuit. I have it working but the multiplexing flickers too much and the counter takes 15 seconds to count from 1 to 2, then 15 seconds from 2 to 3 etc. Any idea on how I can speed this up? Thanks for any help or ideas.

By: Amit Rana

Amit Rana — Fri, 19 Aug 2011 12:50:43 +0000

only one request!!!
it happens with many people in learning phase that they
don’t read technical details and start experimenting so
it happens that they ask few questions, which seems absolutely silly for us, like the one above about static variable,
try to be little polite, you are doing a very nice job of teaching people free of cost, that’s a very good task, but it happens that sometimes you are too harsh
Anyways you rock man!!

By: Amit Rana

Amit Rana — Fri, 19 Aug 2011 12:48:03 +0000

great work
nice job done!!!

By: shayan

shayan — Sat, 13 Aug 2011 09:46:21 +0000

Can multiplexing be seen via simulation On PROTEUS ??

By: shayan

shayan — Sat, 13 Aug 2011 09:45:23 +0000

Can multiplexing be seen via simulation ?? On PROTEUS ??

By: shayan

shayan — Sat, 30 Jul 2011 10:34:42 +0000

@Avinash Did u get the mail i sent u of the program in which u have asked for the example to display digits using an array ??

By: Avinash

Avinash — Thu, 28 Jul 2011 03:17:04 +0000

@Shayan,

Can you write the complete code, test it and submit ???

By: shayan

shayan — Wed, 27 Jul 2011 16:35:27 +0000

Hello !! your logic is good but why do you use switch-case statement for 0-9 counting. The better (shorter) way (i think) is to make an array first containing all codes for displaying 0-9 digits. Now whenever a number is to be displayed, the array will itself call that code in its respective number for e.g. if 2 is to be displayed then the 3rd element of array should give that code to 7segment. Do u understand ? If yes do u agree ?? Thats my approach of displaying digits .

By: mohamed elbardiny

mohamed elbardiny — Fri, 10 Jun 2011 07:43:18 +0000

hi,
i read the tutorial about multiplexing three 7 segment and i have segment lcd with 40 pin its model twv1302n and i need help to apply the multiplexing theory on it
thank you alot

By: rafi

rafi — Wed, 23 Mar 2011 21:47:39 +0000

hi,
Avinash
you r awesome man.u done a great job.i must say ur teaching skill on avr is great.easy to understand and applicable for beginners.why don’t u write a book for the beginners???it’s a great idea.Are u start working on 8*8 dot-matrix display??if so then post ur tutorial about dot-matrix.i m thankfully waiting for this.and once again god bless u………..u r absolute genius.

By: Domos

Domos — Fri, 11 Mar 2011 22:49:42 +0000

I do not think I was aggressive in my question, unless this is due to my broken English.
Programming is just a hobby for me

By: Avinash

Avinash — Fri, 11 Mar 2011 03:47:44 +0000

@Domos

can’t you notice “static” before the variable declaration?

Consult a book on C for definition of “static” variable rather than guessing whatever you like.

By: Domos

Domos — Tue, 01 Mar 2011 13:50:22 +0000

Thanks, for this code.
But there is a thing I don’t understand in the interrupt function:

ISR(TIMER0_OVF_vect)
{
static uint8_t i=0;

if(i==2)
…

The variable “i” is declare with the value “0″.
The test “if(i==2)” will never be true.

And the last line “SevenSegment(digits[i],0);” will alway display the digit “1″ because the i++ line before.

Can you explain me ?

By: Ian Smith

Ian Smith — Tue, 11 Jan 2011 19:15:21 +0000

great tutorials!
I have done a 5-page PDF of the seven segment MUX tutorial with PagePlus,which i will gladly send for you to put on the site

By: Avinash

Avinash — Sat, 25 Dec 2010 11:27:47 +0000

@Arturas,

I think you have used wrong type of transistors, so when they should be in “on” condition they are actually “off” and vice-versa. So check your transistors. Use exact type shown in tutorial.

By: Arturas

Arturas — Thu, 23 Dec 2010 13:17:25 +0000

Hi! I have problem with 3x7segment display. After writing hex to mcu i get it working, but somehow it’s malfunctioning (made video with slow motion to better understand problem http://www.youtube.com/watch?v=QAGBkIZ13DI it does look like it turns 2 sections of lcd at a time) Any solutions in changing code? I use 7segment lcd’s with common + and atmega32 with internal oscilator (i think at 8mhz). I use WinAvr + Programers Notepad. Making hex i get 3 warnings:
c:98: warning: function declaration isn’t a prototype
c:135: warning: function declaration isn’t a prototype
c:134: warning: return type of ‘main’ is not ‘int’
Tryied compile code for attiny2313, but it doesn’t alow, geting few errors.