USB to serial with COM port LCD display

Avishay writes informing us of his recent project, a USB-to-serial adapter with a small display that shows the COM port number of the adapter once connected to the computer. The design is based on an 18F2553 dev board. Avishay reports his project was the recipient a $250 2012 Wyolum innovation grant.

This project is still in the beta stage, with no RS232 line driver and only a single-digit port number display. Nevertheless, it looks like a potential timesaving concept, eliminating the need to check the OS for the COM port assignment every time a device is plugged in.

Visit Avishay’s website for project details and source code.

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  1. It’s a good ideia and should be easy enough to port the host app for Mac and Linux, once the one digit limitation is fixed.

    1. Sorry, I typed that on my phone, android doesn’t like big textareas or something. The cursor tends to jump around so you don’t know what you are editing or deleting.

      Anyway, this could be done with 8 leds as well. ( that is what I wanted to say ) One byte would show 0-255 which most computers would fall into as far as serial ports. I could be wrong, though. Even still, the one byte worth of leds is better resolution than the lcd because it is not limited to just one digit. Ultimately, something that indicated the port number on the FTDI ( or whatever ) could be helpful.

      If I can’t get it at a glance I usually unplug the device I am trying to use and replug it in while looking at the device manager… Not really a big issue for me, but I like that he found a problem and worked on a resolution. If nothing else he has the satisfaction of making headway on his project and I am sure he has learned something.

      The best skill to have is the ability to trouble shoot. Even though my son is only 15 months old, I love watching him try to figure some things out. It is also fun to help him in the process, but really just presenting opportunities for him to realize a solution.

      Good job, Avishay. :)

  2. I suspect OpenMakersDaily is correct about it needing a dedicated application on computer, I was thinking the same thing.

    However if you’re going to go to the trouble of making a dedicated app for the computer end, then why bother with the hardware at all? You could simply make the app reside there and popup from the system tray (or pop-up or whatever) for a set period of time whenever it setup a new VCP. So if you plugged in your fancy VCP device, it would bring up a small dialog that it had just opened Com Port 3 or whatever and that message would stay up for 10 or 15 seconds or whatever you decided.

    For that matter, you could right click on the app in the system tray and it could show the Com ports from left to right as they had been setup, so if it setup Com3 last, that would be the right-most Com Port Number displayed. This way you could check at any time if you missed the display message because you were poking around the back of your computer at the time.

  3. Thanks for all the comments!
    openmakersdaily is right – a host side application is needed. There is no other way a device can know which COM port was assigned to it.
    As to Sleepwalker3 comment, the idea is to have a direct indication about the COM port, even when you’re using several adapters at once, without having to connect and disconnect them.
    I’m planning to continue the development (PCB etc.). I’ll update on my blog.

  4. Yes I see your point Avishay. I do wonder about something though. With this device connecting directly to the USB, it’s fine for identifying what com port your device is connected too, but if XYZ USB-RS232 adaptor is connected, presumably you would have to connect your device to the RS232 end of that adaptor?

    To overcome your problem of not enough digits, have you considered using one of the little dirt-cheap Nokia displays that Greeeg used and was shown on DP? They were selling for about $2.50 before the DP article, now about $4.50 (delivered!) but still very cheap. They can run SPI and I believe they may also have I2C and async serial also.×68-monochrome-lcds/

    Presumably you only run your program for a moment and then close it, as otherwise it would keep control of the port and the original intended application couldn’t use that port?

    A MAX232 will give you RS232 levels cheaply, but if you’re really trying to save every cent, you could make a simple resistive divider with two resistors and use that on the Tx line from the computer. I think many of the adaptors only output 5V anyway, which from memory is still within the RS232 specs.

    1. RE:”Presumably you only run your program for a moment and then close it, as otherwise it would keep control of the port and the original intended application couldn’t use that port?”

      It is cdc + hid, the port data is send to the HID.

  5. Actually, that LCD is back down again to $2.98, sales must have dropped again after the DP article caused initial heavy traffic.

      1. It looks like a solder only connector to me.

        Actually they look more difficult to solder then they are. The key part is a good pcb with a good footprint and some flux. align it properly and flux it, put some solder on your tip and heat the contacts. THe solder should flow and bond the display to the pcb together.

      2. There is always the friction method, you remeber before micro connectors (which are really just friction connectors with a shell), they lay out a bare copper section and then screw down a strip of metal with a bit of sponge between the metal and flex cable.. ?

        Used to see them in calculators and the like on the lcds. They’re dead cheap, with conductive ink on the pcb, tinning probably works too but I don’t recall seeing it done.

      3. @AndThen – Yeah I know that method, hadn’t thought of that, though I don’t think I’d use it in this case, you’d need to have a reasonably accurate guide or reference to keep the thing aligned to the PCB. with a 0.6mm pitch, it doesn’t need to be out by much.

        I got a DP 0.65mm Dangerours Proto board which hopefully is close enough to align up to solder. I was thinking of something more along the lines of this
        but seems nothing as available in 0.6mm. So, looks like it’s solder to a 0.65mm board or make a breakout board to suit.

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