Re: 1-wire to USB converter that can use 1820s directly

["Rod Speed" <rod.speed.aaa@xxxxxxxxx>]

Marc F Hult <MFHult@xxxxxxxxxxxxxxxxxxxxx> wrote
> Rod Speed <rod.speed.aaa@xxxxxxxxx> wrote
>> Marc F Hult <MFHult@xxxxxxxxxxxxxxxxxxxxx> wrote
>>> Rod Speed <rod.speed.aaa@xxxxxxxxx> wrote
>>>> Marc F Hult <MFHult@xxxxxxxxxxxxxxxxxxxxx> wrote

>>>>> 5) Despite what OP writes, Dr Anderson's site does indeed
>>>>> include schematics and explanations for the devices in question.

>>>> Maybe you could post the precise url for the schematic for say
>>>> http://www.phanderson.com/tm128/tm128.html

>>> Sure:

>> Nope.

>>> here's the interconnect diagram:
>>> http://www.phanderson.com/tm128/tm128_config.jpg

>> Not the schematic, you cant see how he's
>> powering the 1wire strings from that.

> If one connects pin 3 of a  DS18x20 to V+, the chips
> are powered; if not, they run in parasitic mode..

Duh, thats in the datasheet.

That aint what HE had done 1wire bus master wise.

It isnt even obvious what he is using
as a 1wire busmaster either PIC wise.

So we know that whatever he is doing does drive strings of 1820s
fine, but we dont have much detail on how he is driving them.

> The diagram shows *clearly* that pin three of the "DS18S20 or
> DS18B20 or DS1822" is connected to the wire that interconnects
> "Pin 1 GND" on the DS2438 to "Black (GRD) " on the TM # 128.
> And that position 5 on the #128 connector is "Black ground".

> So the two channels are being powered by data lines on pin 2
> in parasitic mode, not by V+ on pin 3. There are also 4.7k
> resistors in series with the PIC data lines to protect the PIC.

See above.