« previous topic   next topic »
Pages: [1]   Go Down
Author Topic: I2C between 8MHZ & 16 MHz arduinos  (Read 706 times)
0 Members and 1 Guest are viewing this topic.
magnethead794
Ft. Worth, Texas
Offline Offline
God Member
*****
Karma: 0
Posts: 591
View Profile
« on: August 31, 2012, 09:47:43 pm »
 Bigger Bigger Smaller Smaller Reset Reset
Any issues with doing it? Just wondering. Need to link a FIO and a mega over I2C.
Yes I know level conversion will be needed.

(the other end of the xBee link is a FIO & teensy2.0++ pairing..same deal there)
« Last Edit: August 31, 2012, 09:54:59 pm by magnethead794 » Logged
KF5RVR

frank26080115
0
Offline Offline
God Member
*****
Karma: 0
Posts: 594
View Profile
« Reply #1 on: August 31, 2012, 10:29:20 pm »
 Bigger Bigger Smaller Smaller Reset Reset
there shouldn't be any issues

level conversion will not be needed, just disable internal pull-up resistors and use external pull-up resistors that "pull" to 3.3V
Logged
Freelance engineer, consultant, contractor. Graduated from UW in 2013.

magnethead794
Ft. Worth, Texas
Offline Offline
God Member
*****
Karma: 0
Posts: 591
View Profile
« Reply #2 on: August 31, 2012, 10:43:13 pm »
 Bigger Bigger Smaller Smaller Reset Reset
Quote from: frank26080115 on August 31, 2012, 10:29:20 pm
there shouldn't be any issues

level conversion will not be needed, just disable internal pull-up resistors and use external pull-up resistors that "pull" to 3.3V

So the 5V signals coming from the 5V board won't overdrive the 3V3 pins?
Logged
KF5RVR

James C4S
Austin, TX
Offline Offline
Faraday Member
**
Karma: 71
Posts: 6133
Baldengineer
View Profile
WWW
« Reply #3 on: August 31, 2012, 10:46:08 pm »
 Bigger Bigger Smaller Smaller Reset Reset
Quote from: magnethead794 on August 31, 2012, 10:43:13 pm
So the 5V signals coming from the 5V board won't overdrive the 3V3 pins?
That's why you use external pull-up resistors.
Logged
Capacitor Expert By Day, Enginerd by night.  ||  Personal Blog: www.baldengineer.com  || Electronics Tutorials for Beginners:  www.addohms.com

magnethead794
Ft. Worth, Texas
Offline Offline
God Member
*****
Karma: 0
Posts: 591
View Profile
« Reply #4 on: August 31, 2012, 10:51:40 pm »
 Bigger Bigger Smaller Smaller Reset Reset
Quote from: James C4S on August 31, 2012, 10:46:08 pm
Quote from: magnethead794 on August 31, 2012, 10:43:13 pm
So the 5V signals coming from the 5V board won't overdrive the 3V3 pins?
That's why you use external pull-up resistors.

Doesn't make sense to me, but I'll go with it.
Logged
KF5RVR

James C4S
Austin, TX
Offline Offline
Faraday Member
**
Karma: 71
Posts: 6133
Baldengineer
View Profile
WWW
« Reply #5 on: August 31, 2012, 10:54:38 pm »
 Bigger Bigger Smaller Smaller Reset Reset
Research "open collector".

The I2C pins are open-collector.  They need to be pulled-up so if you external resistors and pull them up to 3.3V they become 3.3V pins.
Logged
Capacitor Expert By Day, Enginerd by night.  ||  Personal Blog: www.baldengineer.com  || Electronics Tutorials for Beginners:  www.addohms.com

magnethead794
Ft. Worth, Texas
Offline Offline
God Member
*****
Karma: 0
Posts: 591
View Profile
« Reply #6 on: August 31, 2012, 10:58:52 pm »
 Bigger Bigger Smaller Smaller Reset Reset
Quote from: James C4S on August 31, 2012, 10:54:38 pm
Research "open collector".

The I2C pins are open-collector.  They need to be pulled-up so if you external resistors and pull them up to 3.3V they become 3.3V pins.


works for me.
Logged
KF5RVR

Pages: [1]   Go Up
« previous topic   next topic »
Jump to: