On Sat, Feb 13, 2021 at 11:58 AM Trevor Woerner <twoerner@xxxxxxxxx> wrote:
Hi,
It's true that you do need a device tree overlay to tell the kernel that you
want to use the 1-wire bus, and you have to tell the kernel which GPIO pin you
want to use as the 1 wire, but after that, attaching DS18B20 devices to a
running system works quite magically.[4]
Each DS18B20 has a unique 64-bit number burned into it, the first 8 bits
specify the device type (i.e. the DS18B20), the next 48 bits are a unique
serial number, and the last 8 bits are a CRC of the previous 56 bits. Due to
the inclusion of the 8-bit device type, when I plug a DS18B20 into my board,
the kernel automatically creates a sysfs entry for it with a "temperature"
file that I can read to obtain the temperature in Celcius.
so, this device looks discoverable on a bus,
once you know the bus is there.
thats the 1st distinction to make.
there are degrees/features.
Id also ask:
is that ID at a standard location ?
via some base transaction that all devices support ?
in my own house, I can find a switch in the dark.
I dont have Alexa listening to render help.
I don't know if that qualifies as "discoverable"? It's certainly a lot more
discoverable than I2C or SPI, although maybe not quite as discoverable as,
say, PCI. Specifying the 1 wire is not discoverable, but plugging 1-wire
devices into my board is maybe something that could be described as
discoverable?
Best regards,
Trevor
[1] https://www.youtube.com/watch?v=a9CZ1Uk3OYQ
[2] https://twoerner.blogspot.com/2020/12/temperature-readings-with-ds18b20-and.html
[3] https://twoerner.blogspot.com/2021/01/sensing-temperature-with-raspberrypi.html
[4] https://twoerner.blogspot.com/2020/12/multiple-ds18b20-temperature-probes.html
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