Going from Serial (RS-485?) to a mobile device

Discussion in 'The Projects Forum' started by anvijost, Jun 10, 2015.

  1. anvijost

    Thread Starter New Member

    Jun 10, 2015
    So, I have a project that I'm not quite sure how to get started on. I need to get serial output from a digital panel meter (currently using one with RS 485 output but that can change) to a mobile device, either Android or Windows. The eventual goal is to get the numbers displayed on 2 different meters to show up on an Android/Windows tablet, and to do some simple calculation with those numbers.

    I'm familiar with Android and software development, so I dont think making a simple app for either OS is really my limiting factor. The real issue is that I am unfamiliar with RS 485, and there's limited information out there in terms of tutorials and instructions on how to get information from this port. I have done a little work with microcontrollers so my initial idea was to somehow go from RS 485 to Arduino/microcontroller to Bluetooth/internet to the tablet, but the first step is getting data from the digital meter.

    I don't exactly know how to get started, and maybe this is the wrong place to ask, but hopefully someone can help me get a better idea of what I should be doing/where else I can look to learn how to do this. I have some leeway in terms of what devices are being used, so I can change the digital meter to one that has an RS 232 output if that helps (possibly even one with USB but I'm not sure). The microcontroller needs some way to wirelessly communicate with a tablet but as long as it meets that requirement, I don't have anything specific in mind. I've looked up "RS485 to Arduino", and there are a few products that seem applicable (RS485 shield, TTL to RS-485 module) as well as a few threads on other forums, but I'm still having trouble figuring out how exactly I'm going to get the data from the meter to some format that a programmer would be familiar with.

    Sidenote: at least one digital meter I've looked at has had some functionality called Devicenet that just from the name seems like it might do some kind of wireless communication which would let me cut out the Arduino middleman. If anyone knows what Devicenet is and what it does, I would greatly appreciate if you told me whether it's something I should look into.

    Thanks for all the help!
  2. AnalogKid

    AAC Fanatic!

    Aug 1, 2013
    RS-485 is a physical layer protocol, like RS-232 for PC serial ports. It is faster and more reliable, especially over long distances, but does not have any specific data format. To get it into a small microcontroller board, you can convert it to RS-232 to use a standard serial port. Or buy a meter with an RS-232 interface. That covers the hardware interface. Beyond that, you need to find out the data format of the panel meter. It might be bi-directional, in that you send it a command and it sends back data. In the PC world, these things can be controlled using a serial port and Hyperterminal, the Windows application for text-based serial communications (like a chat window for the meter). Can't get more specific without more specifics, but you'll need to get the programming/user/interface manual for the meter to learn how to talk with it.