----- Original Message ----- From: "Jason Wolfson" To: Sent: Tuesday, October 03, 2000 4:51 PM Subject: [EE][PIC] Long distance I2C > I'm trying to run a remote I2C temp sensor over phone > cable 50m away into a PIC. It needs to be very reliable and cheap. > > My first assumptions are: Run slow out of the PIC since I can > control the bit rate and therefore reduce effect of slew due to cable > capacitance. > > Second, use a driver of some sort out at the I2C sensor to isolate > the I2C sensor chip from cable capacitance/impedance and protect from > induced transients. > > Has anyone done this and know all the "gotcha's"? > Easiest way of implementing a driver/receiver circuit? > Transient protection? etc.... You might like to look at the Philips I2C extender chip P82B715 and http://www.semiconductors.com/acrobat/applicationnotes/AN444.pdf "Using the P82B715 I 2 C extender on long cables" From the summary: The P82B715 I 2 C Buffer was designed to extend the range of the local I 2 C bus out to 50 Meters. This application note describes the results of testing the buffer on several different types of cables to determine the maximum operating distances possible. The results are summarized in a table for easy reference. and http://www.semiconductors.com/acrobat/applicationnotes/AN452.pdf Application Note AN452 "One Mile Long I2C Communication using the P82B715" LONG DISTANCE I C DESIGN CONSIDERATIONS Summary I 2 C communication is possible over very long distances, but at greatly reduced data rates. Tests were made and results shown for cable lengths exceeding one mile. This report explores the design considerations and trade-off needed to implement a successful long distance I 2 C communication system. Even if you don't use their chip there's quite a bit of useful information there. -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu