My (Beginners-ish) Project:Help

Palm

New Member
#1
I am currently using a PICAXE-08M microchip on a breadboard. For my project, I want to control 8 7-Segment LEDs, in a sort of Countdown Timer that counts down from a pre-programmed number.

My question is this: Is their a way to get this working without having to purchase difficult chips (EX:Max7219)??

Please note that I am fairly new to all of this, so don't come down hard on me with stupid advice...
 

Brietech

Senior Member
#2
short answer: no. You probably need a microcontroller with more pins on it to control that man seven-segment displays in a reasonable way (an 18X or 28X-1, for instance).
 

manuka

Senior Member
#4
Just how high is your preset number? 10 ^8 ? How rapid is the countdown? There may be clever work arounds involving hacked calculator displays. Stan
 
#5
You can control as many leds as you like with an 08M if you use HC595 serial to parallel chips. These can be added one after the other and each one gives 8 outputs.
 
#6
There is an example in Picaxe Green Book controlling 4 segments using picaxe 08 and 74xx595 uses lookup to convert the codes for the display
 

boriz

Senior Member
#9
Another job for the M5450 LED driver?

Datasheet:<A href='http://www.ortodoxism.ro/datasheets2/e/0zqj6og5wcoq8y1zyxt7r79056py.pdf' Target=_Blank>External Web Link</a>
 

Palm

New Member
#10
Wow, the M5450 display driver looks like the perfect solution. It even show connecting up 8 digits, which is exactly what I need...

OK, again I am new to this stuff, but why does the (M5450) have both a DATA and CLOCK IN? What's the difference?
 

hippy

Technical Support
Staff member
#11
DATA : Set what you want on that line, zero or one, LED off or on.

CLOCK : Pulse it to push that data into the chip.
 

boriz

Senior Member
#12
Yes. The clock input tells the M5450 to accept (&#8216;clock in&#8217;) the data bit currently on the data line. Each &#8216;tick&#8217; of the clock shifts one bit of data into the M5450. A &#8216;tick&#8217; is the clock line going high then going low again. A tiny delay is required between setting the clock high then low (consult the data sheet), BUT the relative slowness of the PICAXE may itself be sufficient to provide an adequate interval as part of it&#8217;s normal processing. This kind of data clocking is a common method of inter-chip communication. The main thing to get right is the timing. Everything else is easy.

EG. If you want to send 0110, then this is what you do:

Set DATA line to zero (low).
Set the CLOCK line high.
Set the CLOCK line low.

Set DATA to one (high).
Set the CLOCK line high.
Set the CLOCK line low.

Set DATA to one (high). *
Set the CLOCK line high.
Set the CLOCK line low.

Set DATA to zero (low).
Set the CLOCK line high.
Set the CLOCK line low.

*Since the DATA line is already high from the previous step, this step may be omitted.


Edited by - boriz on 04/09/2007 05:35:45
 
Top