Am 20.10.18 um 18:22 schrieb Mick Sulley:
> I have a Pi with Sheepwalk RPi3 adapter running multiple temperature
> and I/O. I get random read failures and bus lock up, read failures
> every day or two, bus lock up every week or so.
>
You can't to anything about spurious read and write failures. It's a bus
system, they happen. You have to implement a retry on the hostn side and
failsafe logic on the device side. It can be tricky.
(I just had the problem with a remote on-off switch. Sometimes, the
**off** command is broken. Solution: always use anm on-timeout on the
device. On-commands have to be repeated each few seconds. That way, a
lost instant-off command will not do endless harm.)
About the bus lock-up, that's a bug in the DS2482-800, I think. I had
it. Various other people had it. The DS2482-800 seems to be susceptible
to supply undervoltage and slow rising of the supply voltage. It resets
into an unuseable state. Only a complete power-down and quick power-on
will make it useable again.
Check your power supply.
> Currently I have
> separate power supplies (Meanwell units) for the Pi and the 1-wire
> and they are both floating.
>
> Question - Is there an advantage in linking the 0v on the two
> supplies?
>
You cannot have them floating. The sheepwalk adapter has a shared GND
for both the Onewire and the I²C (Raspberry side).
The individual ports are protected my DS9503 chips, as far as I can see
it from the photos. These have 5Ω resistors in the GND lines of each
connector. A good thing, do not change that.
> Also should the 0v be connected to the mains earth?
>
Don't do that. It will give you **less** noise immunity and also fry the
low voltage circuit as soon as some high voltage circuit has a ground fault.
Kind regards
Jan
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