Sampling 24V one wire serial? - Page 1
Forum section: electronics / beginners

author: Borillion
author_rank: Newbie
timestamp: June 24, 2023, 09:24:15 pm
content: I would like to sample 24V one wire serial with a voltage divider, wouldn't grounding the resistors in series potentially affect the data being transmitted?This is for the nanoleaf Aurora which is documented here on a tear downhttps://www.eevblog.com/forum/projects/nanoleaf-aurora-teardown/and some of the protocol in use is explained herehttps://kronoshacker.blogspot.com/2018/01/playing-with-aurora-led-panels.htmlQuote :The Comm Pin ( this case the pin name is officially labeled vbus )The Comm Pin is used for data communication between the tiles. It is a open collector bus which can be driven to low by any tile. The protocol must take care of collision avoidance. RS232 at 115200 Baud, 8N1 is used for the communication on this pin. Inactive level is 24V, Active level is 0V. The signal is pulled to 24V by the controller. The tiles drive the signal to GND via a open collector circuit.In this it appears that 0V is a 1 value ( mark? ) and 24V is a 0 ( space? )I was considering using an optocoupler but I am uncertain about how to select the correct type for a 115200 baud, half-duplex, 8-N-1, UART signal that is responsive enough.My experience level is use of platforms like the Arduino and Raspberry pi, ftdi USB to TTL UART and 3V/5V level shifters, and software libs provided to make them work. A software developers view, bits and bytes. While I know how to use things like shift registers, resistors and controllers to handle servos and led matrices. This is somewhat out of my expertise area.Appreciate any help, guidance, advice, etc in figuring this outI asked this a stackexchange subdomain and ended up with some pretty condescending what I feel as borderline rude and arrogant commentary. 😵‍💫

author: DavidAlfa
author_rank: Super Contributor
timestamp: June 24, 2023, 09:33:46 pm
content: Use appropiate resistors which won't load the bus too much, onewire is similar to i2c, but the device powers itself from the bus pullup resistor and stores the energy in a beefy capacitor.Not sure what that device does, but it's a similar concept after all.At 115K you don't need anything fancy, try a high value like 220K/33K, will only draw 100uA, should't affect it, any mcu input should be fine with that.Then just use the UART peripheral!

author: langwadt
author_rank: Super Contributor
timestamp: June 24, 2023, 09:34:12 pm
content: do you only need to receive?

author: DavidAlfa
author_rank: Super Contributor
timestamp: June 24, 2023, 09:45:00 pm
content: Quote from: langwadt on June 24, 2023, 09:34:12 pmI think so?Quote from: Borillion on June 24, 2023, 09:24:15 pmSample, not communicate.

author: Borillion
author_rank: Newbie
timestamp: June 24, 2023, 11:04:36 pm
content: While at this time I will like to only receive the signal and monitor it, in the long run I would like to also transmit, perhaps a mosfet trigger switch which seems to work with aquarium LED controller and an ESP32, but that is a PWM duty cycle and not a serial signal so I am not sure it would actually work out.Currently, I was looking to explore how panels are enumerated and initialized, I have a notion of how its doing it but wanted to compare my theory with what I can sense off of the pins.

author: Borillion
author_rank: Newbie
timestamp: June 24, 2023, 11:08:42 pm
content: Ok that is reasonable. Ground to 24V and then read from the connection between the resistors as I understood it.

author: langwadt
author_rank: Super Contributor
timestamp: June 24, 2023, 11:17:29 pm
content: a pull up to 3.3/5V on your mcu rx pin and a diode from that pin to the 24V bus doesn't load the bus and might work as long as the 0 level is low enough

author: Borillion
author_rank: Newbie
timestamp: June 25, 2023, 12:39:33 am
content: So something like this configuration? ( ignore values )I am also seeing something like this but not super clear on the value of the zener diode.

author: langwadt
author_rank: Super Contributor
timestamp: June 25, 2023, 12:44:57 am
content: Quote from: Borillion on June 25, 2023, 12:39:33 amdiode the other way

author: Borillion
author_rank: Newbie
timestamp: June 25, 2023, 02:12:23 am
content: hah a derp on my part

author: infracodergirl
author_rank: Newbie
timestamp: September 16, 2025, 06:34:10 pm
content: Hello Sir,apologies for waking this ancient thread.I am starting to look into the same topic right now and was wondering whether you ever got anywhere.My controller is still alive, but I figure it's only a matter of time, until I have a massive piece of e-waste on my wall.Buying replacement controllers is just no longer an option.From the reverse engineered communication, you also linked, I have ideas on how the controller probably works/how I would replicate functionality.Code should be doable for me, but the hardware is daunting.I have a background in IT, but I lack experience with electronics.In theory, I am headed towards a project with an ESP32, translating UART via Optocoupler and Logic Level Mosfet.I would appreciate any pointers you may have, of course including failed attempts.Thank you in advance