Forum Index
HomeZBasic Home   Forum RulesForum Rules   Forum FAQForum FAQ   MemberlistMemberlist   UsergroupsUsergroups   RSS FeedRSS Feed
Site SearchSite Search   LinksLinks   DownloadDownload   Digests and SubscriptionsDigests and Subscriptions
ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in   RegisterRegister
Connecting LEDs and Pin configuration

 
Post new topic   Reply to topic    Forum Index -> ZX-24
Author Message
victorf



Joined: 01 Jan 2006
Posts: 342
Location: Schenectady, New York
Posted: 05 January 2006, 11:38 AM    Post subject: Connecting LEDs and Pin configuration Reply with quote
I would like to connect a LED to a ZX on a Port C pin. What is the perferred method to do this. Confused

Also, I guess I do not understand the what the pin configuration mode zxInputTriState and zxInputPullup mean. Could someone characterize these for me?

Any enlightenment will be appreciated

Vic
Back to top
spamiam



Joined: 13 Nov 2005
Posts: 664
Posted: 05 January 2006, 21:15 PM    Post subject: Re: Connecting LEDs and Pin configuration Reply with quote
victorf wrote:
I would like to connect a LED to a ZX on a Port C pin. What is the perferred method to do this. Confused

Also, I guess I do not understand the what the pin configuration mode zxInputTriState and zxInputPullup mean. Could someone characterize these for me?

Any enlightenment will be appreciated

Vic


Well, first: remember that you have a 20mA limit on the current through any one pin. This means that you need a minimum of 250 ohms total resistance for the pin. This is enought to drve most standard LEDs to a very bright light. Many require much less. I would use 470 ohms or more, maybe 1000 ohms.

zxInputTristate means that the pin is being used for input, and is set to a high resistance (no pull-up). zxInputPullup means that the pin is set for input, and also has activated a weak pullup resistor. I think that the pullup is 100K ohms to +5volts. This is enough to eliminate noise on a floating pin, but may not be enough for the circuit connected to the pin. Usually, if you need a pullup, then it is best to add that yourself.

To drive an LED, you would need to set the pin to "output", then it will light up if you have the LED grounded and set the pin to "high". The alternative is to have the LED attached to +5, and then setting the pin "low" will make the LED light.

If you have the pin set to input-pullup, then you might get a LED to light up weakly if it is attached to ground.

-Tony
Back to top
spamiam



Joined: 13 Nov 2005
Posts: 664
Posted: 05 January 2006, 21:20 PM    Post subject: Re: Connecting LEDs and Pin configuration Reply with quote
victorf wrote:
I would like to connect a LED to a ZX on a Port C pin. What is the perferred method to do this. Confused

Vic


I fogot the "preferred" part of the question. I seem to remember that the AVR microcontrollers are better at sinking than sourcing. So, if this is true, the best method is "backwards" (at least to me). Setting the pin to "zxOutputLow" to make the LED light up is preferred to the other way around.

PIN---1Kohm---LED---+5v

-Tony
Back to top
Display posts from previous:   
Post new topic   Reply to topic    Forum Index -> ZX-24 Time synchro. with the server - Timezone/DST with your computer
Page 1 of 1

 


All content Copyright © 2005-2012 Elba Corp. All Rights Reserved.
Opinions expressed in posts are those of the author and not necessarily those of Elba Corp.
Powered by phpBB © 2001, 2005 phpBB Group