5 ms·

Looks cool. Why single wire and not a simple twisted pair? Are you using a voltage relative to earth for your logic states? Just not sure how it could work othe

by nabogh 6y ago

Looks cool. Why single wire and not a simple twisted pair? Are you using a voltage relative to earth for your logic states? Just not sure how it could work otherwise. A twisted pair seems nice to me because you can use differential signaling and not have to ground your devices e.g. 2 wire RS485.

gridspy 6y ago
Radio systems have an antenna that radiate energy into the atmosphere. Other antennas resonate in harmony. What if you just connect the antenna wires of all the devices together? That's what a single wire protocol does.
- im3w1l 6y ago
  I'm not really knowledgeable so excuse me if I have a misunderstanding as I try to reason about this from a different perspective. When you have an object with static electricity and put it in contact with a different object, there will be a transient current, even if the circuit is not closed. The objects basically work as poor-man's capacitors. Even though the name is "static electricity", when the objects come into contact, it's actually more dynamic than normal, because there is no current between two objects of fixed and different voltage. The more current that flows, the lesser the voltage difference becomes, in an exponential fashion. This kind of single wire protocol operates solely based on these kind of transient currents. Because the frequency is so high, very little current flows during one period of the waveform, so the receiver will maintain constant potential, as if it was grounded. That it isn't actually grounded means the signal becomes high-pass filtered. In particular, the DC-component must be completely blocked as it would lead to charge buildup with nowhere to go.
gioscarab 6y ago
Yes the voltage is relative to ground for the logic state, the differential signaling requires a source of negative voltage and a more complex front-end, being relative to ground you just need a digital IO operating at 5v or 3.3v and a ground pin, no additional hardware (although current-limiting and pull-down resistors are suggested), as a result it can be fully and easily bit-banged. The twisted pair (where one wire is the bus and the other the ground) is one of the suggested approaches that helps to reduce the interference induced on the wire.

by nabogh 6y ago

gridspy 6y ago

Radio systems have an antenna that radiate energy into the atmosphere. Other antennas resonate in harmony. What if you just connect the antenna wires of all the devices together? That's what a single wire protocol does.

im3w1l 6y ago
I'm not really knowledgeable so excuse me if I have a misunderstanding as I try to reason about this from a different perspective. When you have an object with static electricity and put it in contact with a different object, there will be a transient current, even if the circuit is not closed. The objects basically work as poor-man's capacitors. Even though the name is "static electricity", when the objects come into contact, it's actually more dynamic than normal, because there is no current between two objects of fixed and different voltage. The more current that flows, the lesser the voltage difference becomes, in an exponential fashion. This kind of single wire protocol operates solely based on these kind of transient currents. Because the frequency is so high, very little current flows during one period of the waveform, so the receiver will maintain constant potential, as if it was grounded. That it isn't actually grounded means the signal becomes high-pass filtered. In particular, the DC-component must be completely blocked as it would lead to charge buildup with nowhere to go.

gioscarab 6y ago

Yes the voltage is relative to ground for the logic state, the differential signaling requires a source of negative voltage and a more complex front-end, being relative to ground you just need a digital IO operating at 5v or 3.3v and a ground pin, no additional hardware (although current-limiting and pull-down resistors are suggested), as a result it can be fully and easily bit-banged. The twisted pair (where one wire is the bus and the other the ground) is one of the suggested approaches that helps to reduce the interference induced on the wire.