Am 22.07.2016 um 12:30 schrieb Henrik Östman:
> Hi!
>
> I have a self soldered circuit board containing a DS2480 and a
> Max232-converter, back in the old days it was connected directly to the
> serialport of a computer but nowdays I'm using a USB-serial converter
> connected to a Raspberry Pi. Thinking about it it makes no sense
> converting the signal to a RS232-level and back again, it only makes the
> installation more complex and more troublesome to faultfinding.
> Should'nt it be possible to connect the DS2480 directly to one/two pins
> on the Raspberry
>
The GPIO pins of the Raspberry are 3.3V. The DS2480B is not compatible
to 3.3V, you need a 3.3V->5V level shifter. This can be an IC, or two
MOSFETS (e.g. BS170, 2N7000) and two 1.5k to 4.7k resistors on the TxD
and RxD lines. Do you need the 12V EPROM programming?
Because the easiest way to have Onewire on the Raspberry is using GPIO4
and let the w1 kernel driver bitbang the protocol. If you want a 5V
Onewire, you need a single MOSFET and resistor again as the level
shifter. Note: no strong pullup available with 5V level shifting in this
case.
The alternative I recommend is to use the DS2483. It's 3.3V compatible
on its I2C inputs and gives you a 5V Onewire with all features but 12V
EPROM programming on its output. Plus, the single RS232 port the
Raspberry has stays free for console and other purposes.
> and use a suitable driver? Could anyone point me to
> which driver to use, how should owfs.conf be setup to support this, and
> which pins on the Raspberry Pi should I connnect to?
>
Choose your poison first.
Kind regards
Jan
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