Linux 5.4 Bringing New Driver To Help SGI Systems Going Back To The SGI Origin

[phoronix]

Phoronix: Linux 5.4 Bringing New Driver To Help SGI Systems Going Back To The SGI Origin

SGI systems going back to the SGI Origin servers starting some two decades ago will see better mainline kernel support with the upcoming Linux 5.4...

http://www.phoronix.com/scan.php?page=news_item&px=Linux-5.4-SGI-One-Wire

[madscientist159]

OneWire! That's a technology I haven't seen in the wild in a long, long time. I actually did a FPGA master for it well over a decade ago; interesting tech, but not exactly aimed at use in systems with a common VCC/ground already available. The more interesting uses for it involved a sort of long single-wire bus-powered network, lacking the ground loop problems of more traditional multi-wire interfaces. Think IoT before $3 sensors with more traditional network interfaces became available, that kind of thing (long sensor chain with room temp sensors for building automation, etc.).

[SystemCrasher]

OneWire! That's a technology I haven't seen in the wild in a long, long time.

Seriously? DS18B20 and so on are still quite popular thermal sensors, so you're quite likely to find some in random nearby electronic components shop. DS1990A "dallas buttons" still used by some cheap access control systems, etc and I guess there're many millions of 1990As in the world. Yet 1-wire isn't without its limits. Say it gives a very limited power budget for devices without power source - so doing e.g. 1-wire slave using MCU could be challenging. And protocol itself is a bit awkward, with fairly low "native" HW support.

As funny hack, 1-wire can be accessed in somewhat simplified manner ... by (mis)using UART hardware (COM ports with level shifter, USB to serial wires, MCU with UART and so on can do that, subject to little hardware "hack" turning them "open drain-like" even if UART is normally "push-pull" output). Same true for similar and exactly strange "HDQ" protocol, sported by iPhone batteries (well, Ti charge gauge IC inside). Basic UART conversion can be as simple as 1 diode+resistor, though there're circuits using BJT(s) or FET(s) to achieve same result.

As for IOT I guess it rather impractical due to very limited power it can provide (which is lost upon bus communication), need to put wirings, and overall it not really meant to run beyond few meters if I remember. Though I've read formal specs hell a long ago and maybe I've forgot something.