Charles, Thanks for your response.
I read the section you mentioned from the I2C standard and it seems that, for this to work properly, there has to be pull-up resistors on both sides of the FET, which doesn't solve my problem. Maybe I didn't understand something, but if I don't pull-up the I2C pins of the BBB, the lines will never go high, because the FET will be in its off state. I want to avoid pulling the I/O pins high before the BBB is fully powered on. On Thursday, June 5, 2014 12:47:53 PM UTC-3, Francisco Aguerre wrote: > > Hi everyone, > > I'm trying to interface a RTC with my BBB using the I2C bus. The reference > manual states that none of the pins in the expansion connectors should be > driven while the system is not powered on. I have isolated other inputs > using tristate buffers and the SYS_RESETn, but the I2C lines, being > bidirectional is a bit trickier. Is it necessary in this case to isolate > the lines during power up? I'm connecting the pull-ups to the +3v3 pin on > the expansion connector. > > If I should isolate the lines, what's the best method? I'm thinking of > using a cmos switch to disconnect the resistors during power up, but maybe > there are better ideas. > > Thnaks! > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
