Hey... These are two contradictory answers... ;-)... Thanks for the reference document, Al. I'll surely read it and see how I can *safely* convert from 3.3V to 5V.
I'm a bit afraid of what Frédéric wrote, when he said he destroyed already two I/O pins like that. Certainly not what I want, of course... Best rgds, --Geert --- In [email protected], SailorAl <[EMAIL PROTECTED]> wrote: > > I have not tried what you propose, but from my understanding of 5v tolerant inputs it should be fine. Here is some additional information. > http://www.standardics.nxp.com/support/documents/i2c/pdf/an97055.pdf > > Al Langer > > ----- Original Message ----- > From: Geert Vancompernolle > To: [email protected] > Sent: Friday, December 01, 2006 9:36 AM > Subject: [foxboard] Output pins 5V tolerant: a question. > > > > Hi, > > I read in the documentation that all pins on the two 40 pin connectors > are 5V tolerant. > > I'm currently using the I2C pins of the connector and they're > connected to two series resistors of 100 Ohm (one for clock, one for > data), which are connected to a PCF8574 device. > > The PCF8574 device is powered with +5V (also coming from the 40 pin > connector). The signal levels of the I2C bus are 3.3V at the I2C > inputs of the PCF8574. I know this is sufficient, but I would like to > use a pull-up resistor of 5k6 to +5V for both SDA and SCL to increase > the level to +5V. Like this: > > +5V > | > _ > | | > |_| > | ___ > SDA-FOX ------|___|----> SDA-PCF8574 > > Same for SCL. > > Is this allowed? Will I not harm the I/O ports of the FoxBoard? > > Best rgds, > > --Geert > > > > #ygrp-mlmsg { FONT-SIZE: small; FONT-FAMILY: arial,helvetica,clean,sans-serif}#ygrp-mlmsg TABLE { }#ygrp-mlmsg SELECT { FONT: 99% arial,helvetica,clean,sans-serif}INPUT { FONT: 99% arial,helvetica,clean,sans-serif}TEXTAREA { FONT: 99% arial,helvetica,clean,sans-serif}#ygrp-mlmsg PRE { FONT: 100% monospace}CODE { FONT: 100% monospace}#ygrp-mlmsg * { LINE-HEIGHT: 1.22em}#ygrp-text { FONT-FAMILY: Georgia}#ygrp-text P { MARGIN: 0px 0px 1em}#ygrp-tpmsgs { CLEAR: both; FONT-FAMILY: Arial}#ygrp-vitnav { FONT-SIZE: 77%; MARGIN: 0px; PADDING-TOP: 10px; FONT-FAMILY: Verdana}#ygrp-vitnav A { PADDING-RIGHT: 1px; PADDING-LEFT: 1px; PADDING-BOTTOM: 0px; PADDING-TOP: 0px}#ygrp-actbar { CLEAR: both; MARGIN: 25px 0px; COLOR: #666; WHITE-SPACE: nowrap; TEXT-ALIGN: right}#ygrp-actbar .left { FLOAT: left; WHITE-SPACE: nowrap}..bld { FONT-WEIGHT: bold}#ygrp-grft { PADDING-RIGHT: 0px; PADDING-LEFT: 0px; FONT-SIZE: 77%; PADDING-BOTTOM: 15px; PADDING-TOP: 15px; FONT-FAMILY: > Verdana}#ygrp-ft { PADDING-RIGHT: 0px; BORDER-TOP: #666 1px solid; PADDING-LEFT: 0px; FONT-SIZE: 77%; PADDING-BOTTOM: 5px; PADDING-TOP: 5px; FONT-FAMILY: verdana}#ygrp-mlmsg #logo { PADDING-BOTTOM: 10px}#ygrp-vital { PADDING-RIGHT: 0px; PADDING-LEFT: 8px; MARGIN-BOTTOM: 20px; PADDING-BOTTOM: 8px; PADDING-TOP: 2px; BACKGROUND-COLOR: #e0ecee}#ygrp-vital #vithd { FONT-WEIGHT: bold; FONT-SIZE: 77%; TEXT-TRANSFORM: uppercase; COLOR: #333; FONT-FAMILY: Verdana}#ygrp-vital UL { PADDING-RIGHT: 0px; PADDING-LEFT: 0px; PADDING-BOTTOM: 0px; MARGIN: 2px 0px; PADDING-TOP: 0px}#ygrp-vital UL LI { CLEAR: both; BORDER-RIGHT: #e0ecee 1px solid; BORDER-TOP: #e0ecee 1px solid; BORDER-LEFT: #e0ecee 1px solid; BORDER-BOTTOM: #e0ecee 1px solid; LIST-STYLE-TYPE: none}#ygrp-vital UL LI .ct { PADDING-RIGHT: 0.5em; FONT-WEIGHT: bold; FLOAT: right; WIDTH: 2em; COLOR: #ff7900; TEXT-ALIGN: right}#ygrp-vital UL LI .cat { FONT-WEIGHT: bold}#ygrp-vital A { TEXT-DECORATION: none}#ygrp-vital A:hover { > TEXT-DECORATION: underline}#ygrp-sponsor #hd { FONT-SIZE: 77%; COLOR: #999}#ygrp-sponsor #ov { PADDING-RIGHT: 13px; PADDING-LEFT: 13px; MARGIN-BOTTOM: 20px; PADDING-BOTTOM: 6px; PADDING-TOP: 6px; BACKGROUND-COLOR: #e0ecee}#ygrp-sponsor #ov UL { PADDING-RIGHT: 0px; PADDING-LEFT: 8px; PADDING-BOTTOM: 0px; MARGIN: 0px; PADDING-TOP: 0px}#ygrp-sponsor #ov LI { PADDING-RIGHT: 0px; PADDING-LEFT: 0px; FONT-SIZE: 77%; PADDING-BOTTOM: 6px; PADDING-TOP: 6px; LIST-STYLE-TYPE: square}#ygrp-sponsor #ov LI A { FONT-SIZE: 130%; TEXT-DECORATION: none}#ygrp-sponsor #nc { PADDING-RIGHT: 8px; PADDING-LEFT: 8px; MARGIN-BOTTOM: 20px; PADDING-BOTTOM: 0px; PADDING-TOP: 0px; BACKGROUND-COLOR: #eee}#ygrp-sponsor .ad { PADDING-RIGHT: 0px; PADDING-LEFT: 0px; PADDING-BOTTOM: 8px; PADDING-TOP: 8px}#ygrp-sponsor .ad #hd1 { FONT-WEIGHT: bold; FONT-SIZE: 100%; COLOR: #628c2a; LINE-HEIGHT: 122%; FONT-FAMILY: Arial}#ygrp-sponsor .ad A { TEXT-DECORATION: none}#ygrp-sponsor .ad A:hover { TEXT-DECORATION: > underline}#ygrp-sponsor .ad P { MARGIN: 0px}o { FONT-SIZE: 0px}..MsoNormal { MARGIN: 0px}#ygrp-text TT { FONT-SIZE: 120%}BLOCKQUOTE { MARGIN: 0px 0px 0px 4px}..replbq { } > > --------------------------------- > Everyone is raving about the all-new Yahoo! Mail beta. >
