One of many reasons to use a 5V tolerant bus master. They're like $1 and worth weight in gold. Probably more (they're tiny).
C > On Oct 1, 2015, at 6:26 AM, Jan Kandziora <j...@gmx.de> wrote: > >> Am 01.10.2015 um 10:10 schrieb Henry Pootel: >> >>> Do you run the onewire with 3.3V from the Raspberry's I/O pin? If so, >>> have you checked all your slaves are 3.3V compatible? >> >> No, I use 5V for Rasberry and for w1 devices. It's one 5VDC power supply. > Henry, all the I/O pins on the pin header of the Raspberry Pi are 3.3V. > The Raspi board is a 3.3V device, 5V is only used for USB power and on > HDMI I²C, all other I/O pins are 3.3V. So if you connect a onewire bus > directly to GPIO4, your bus is run at 3.3V. > > (Both the DS2450 and DS18B20 support a 3.3V bus, the DS2450 still needs > 5V as supply voltage then, however.) > > >> >> And I've 4.7K resistor from the 1-wire to +5V. > Make it 1kOhms and ***tie it to 3.3V*** instead. The Raspberry Pi > doesn't tolerate 5V on its GPIO pins. The only reason you haven't fried > the CPU yet is the current is limited to ~1mA by the resistor. Still, > all kind of odd things can happen if you overvoltage the CPU I/O pins. > Mostly because you are opening protection diodes in the CPU input pin > which may cause timing issues. > > >> >> But I'll check a power line by scope. Thank you for an idea. >> However, I've got the same result with transformer and impulse power >> supplies (220VAC to 5VDC). I think the problem is not in bumps. > I meant bumps on the onewire busline, not on the power line. The > High->Low edges have to be rectangular. If you see bumps between 0V and > 1V on the bus line near a High->low edge it means the host isn't able to > tie the bus to 0V correctly for some reason. > > > Kind regards > > Jan > > ------------------------------------------------------------------------------ > _______________________________________________ > Owfs-developers mailing list > Owfs-developers@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/owfs-developers ------------------------------------------------------------------------------ _______________________________________________ Owfs-developers mailing list Owfs-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/owfs-developers
