Timeline for Bi-directional UART communication on single data wire, possible?
Current License: CC BY-SA 4.0
12 events
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| Sep 5, 2021 at 15:00 | comment | added | st2000 | Yes, that is correct. And it (USB 2.0) can obtain some rather impressive speeds over a good amount of cable run. I think USB 3 use multiple balanced pairs in a full duplex mode to obtain even higher speeds. | |
| Sep 5, 2021 at 14:52 | history | edited | st2000 | CC BY-SA 4.0 |
Added reference to 1-wire definition, libraries and tutorials.
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| Sep 5, 2021 at 14:52 | comment | added | slebetman | @DamnVegetables RS485 needs 2 wires because it is not Data/Ground, rather it is +Data/-Data kind of like USB. Also note that RS485 works best if the two data wires are twisted pair | |
| Sep 5, 2021 at 14:48 | history | edited | st2000 | CC BY-SA 4.0 |
Added reference to 1-wire definition, libraries and tutorials.
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| Sep 5, 2021 at 14:43 | comment | added | st2000 | @DamnVegetables, FYI, you are essentially asking how to design a 1-wire interface over longer than normal distances. I could have just said that in my answer and point you to Arduino tutorials and libraires. But it is likely you will run into problems if your cable is too long. Actually, I think I'm going to put the above in my answer. But, just to help us create a better answer ... just how long is your cable? | |
| Sep 5, 2021 at 14:07 | history | edited | st2000 | CC BY-SA 4.0 |
Addressed long power runs and reasons to use in dependent power supplies. This allows communications over the existing 3 wilre cable using RS485 instead of a reference to ground data channel.
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| Sep 5, 2021 at 12:47 | comment | added | st2000 | @AndreKR, at the end of my answer was a 2 wire solution. It will only work if the remote was powered by some other meas then by cable. And RS485 will almost always out preform a return to ground reference signal. Time and time again people who do not know that try to extend I2C and SPI only to find they can not live w/the noise. I'll amend my answer and explain this more clearly. | |
| Sep 5, 2021 at 11:33 | comment | added | Damn Vegetables | Thanks. Replacing the existing 3-core cable with a 4-core cable is not impossible, but I thought if I had two free wires available for data, I could just connect two Arduino's directly using the TX/RX pins already there. You mean that using RS485 needs two free wires (other than the two for powering the remote Arduino), right? The distance is about 30 metres (=100 feet), and I do not need fast communication (even 100 bps is more than enough). The module called "TTL to RS485" seem cheap. Do you think it is better than direct connection even in my case? | |
| Sep 5, 2021 at 10:53 | comment | added | Damn Vegetables | @AndreKR Yeah, the cable has already been installed (I did), and at that time, I thought I would not need bi-directional communication and 3-core cable was cheaper than 4-core cable, so I chose the former. Now, after using the system, I realised that I need a way to get the status of the remote device. I could remove the old one and install a new cable (not impossible), but it will be such a hassle, so I was looking for a way to do it with the existing wire. | |
| Sep 5, 2021 at 1:41 | comment | added | AndreKR | This might be an XY problem and there might be a hardware solution, but if the question is "how can I make this work with 3 wires" the answer "just use 4 wires" is not helpful. Most likely the cable is already there. If punching through walls to hook up an Arduino would be acceptable OP wouldn't ask the question. | |
| Sep 4, 2021 at 14:48 | history | edited | st2000 | CC BY-SA 4.0 |
added 478 characters in body
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| Sep 4, 2021 at 14:35 | history | answered | st2000 | CC BY-SA 4.0 |