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
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