CCS C Software and Maintenance Offers
FAQFAQ   FAQForum Help   FAQOfficial CCS Support   SearchSearch  RegisterRegister 

ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 

CCS does not monitor this forum on a regular basis.

Please do not post bug reports on this forum. Send them to CCS Technical Support

I2C pull-ups on 18F14Q41 need WPU active?

 
Post new topic   Reply to topic    CCS Forum Index -> General CCS C Discussion
View previous topic :: View next topic  
Author Message
Woody



Joined: 11 Sep 2003
Posts: 83
Location: Warmenhuizen - NL

View user's profile Send private message

I2C pull-ups on 18F14Q41 need WPU active?
PostPosted: Mon Sep 09, 2024 3:29 am     Reply with quote

I managed to forget to put two pull-ups on a prototype I'm working on. No immediate need to heat up the soldering iron, because for birdbrains like me the 18F14Q43 contains I2C pull-up circuitry. Good thing I did use the 'standard' pins for I2C and the distance the bus covers on this PCB is 35mm.

After browsing the forum I saw mentioned more than once that, to make this work, not only the RxxI2C registers need to be set but also the WPU register for the I2C ports.

As I see no difference in risetime (~120ns @10x current) when enabling / disabling WPU for these pins I am wondering if this is still a valid suggestion or maybe just not needed this particular chip?

And while I sort of know the answer but keeping in mind that I only have one I2C slave on a short bus and I meet its .3uS max rise/fall time, would you use the internal I2C pull-ups on a production board? Or just no, not ever?
Ttelmah



Joined: 11 Mar 2010
Posts: 19495

View user's profile Send private message

PostPosted: Mon Sep 09, 2024 6:34 am     Reply with quote

On this chip the I2C PU settings, allow you to select to use the standard weak
pull-up _or_ the I2C pull-ups (only on pins with this available).
Because you have used the standard pins (hurrah), you can set these bits
and get 2* the standard current or 10* the standard current (or 5/20*
when fast mode is enabled) This is independent of the standard weak
pull-ups. If you selected to use the standard pull-ups, they would have to be
enabled.

On quite a few older chips it is the standard pull-ups that are actually used,
with the option to increase their current. On these the weak pull-ups have to
be enabled.

Does not apply to this chip.

Turning the default pullups on should make a tiny difference, but only
a few percent. possibly a couple of nSec, but no more.
Display posts from previous:   
Post new topic   Reply to topic    CCS Forum Index -> General CCS C Discussion All times are GMT - 6 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group