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  1. #11
    Our new friend needs to reach 10 posts to get to the next flight level
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    COM instrument

    Hi,
    I am also trying to make a low cost COM unit.

    My design uses a few building blocks:
    1) display boards (small single sided pcbs for 10mm digits, 16p idc contacts - 3-6 digits)
    2) display controller and reading the swicthes/rotaries
    instrument hardware - test button, transfer button and rotary encoder. RS 232 interface to host

    I use a rotary encoder, with a switch. Press and turn for big digit tuning. I have not found any dual concentric encoders.

    NEarly all parts are in place, breadboard prototype is next step!
    lnola

  2. #12
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    Hi lnola,
    Nice to hear that you are taking the the road of design and assembly. The LED circuit, is it your own design? I would like to hear more when you start wiring-up the panel.

    Capt Bobby

  3. #13
    Our new friend needs to reach 10 posts to get to the next flight level
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    COM unit - divide and conqer?

    Hi,
    I am akso trying to build l low cost COM device, but off course want to display the actual frequency with digits. Presently, the unresolved problem is how to communicate with FS.

    I aim to build the COM as a stand alone instrument, which also greatly simplifies development and testing. I use the serial port, because communication is very low frequence, and it is easy to interface a microcontroller like 16F628. Clearly (?) USB would be a better choice, but would also require a lot more work.

    I think the COM unit may be built with the following sub parts:
    1) communication part, serial to controller.
    2) 2 digit display units each 6 digits and IDC16 to controller.
    3) user input section, two buttons and a rotary encoder
    4) COM front and hardware mountings (glue, strips etc. Only the front will be visible).

    I have completed step 1, and are working on steps 2 and 3, and am trying to tackle the front. At 25 euros they are rather expensive, I guess I can buy one, but for 3-5 fronts for COM, NAV, ADF etc that really adds up and eats the budget away.

    When finished with the steps 1-3, I will have a stand alone COM unit. It will be trivial to make other units of this type. But the problem remains to interface with FS. I need a simple solutions for letting FS send the new frequencies (and display intensity) to the COM device. I have two pins available

    If we remove the ability to send from FS to the device, a cheap USB joystick button interface can be used. I think this is a good solution for the prototype. If doing this, the serial interface is not needed any more.

    What I really need is a program, running on the PC with the FS, that can read FS values and send them to a port or channel (usb, serial etc), and likewise read from the channels. I think this is what FSUIPC do, but it looks like overkill. Considering the data rate, standard serial interface is more than capable to serve all comm units, and probable all instruments in the cockpit. Also, human readable commands and responses should be used, as this helps debugging in a big way.

    Do anyone know of a program like this (prefererable in C), or is FSUIPC the way one must take?
    lnola

  4. #14
    1000+ Poster - Fantastic Contributor Bob Reed's Avatar
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    Well unless you want to reinvent the wheel, FSUIPC does all this for you. There is even a SDK that explains how to use the hooks FSUIPC uses in and out of FS. That is what I would do.
    Bob Reed

  5. #15
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    Hi Inola,

    If you're using FSX deluxe you don't need FSUIPC. FSX deluxe ships with SimConnect, an API that allows you to access flight sim data. SimConnect comes with an SDK which includes numerous examples. Most are written in C/C++. There are a few examples in VB and C# as well.

    I agree that the serial com port is suitable in this application. It's fairly easy to code against. You open it with an Openfile() call. Set the port parameters using GetCommState(), SetCommState() and SetCommTimeouts(). You move data using Readfile() and Writefile(). A good reference for using the serial port is the paper "Serial Communications in Win32" by Allen Denver. It's in the MSDN library at msdn.microsoft.com

    One shortcoming of the serial port is that it's based on RS232C which is a point to point signaling protocol. If you're just getting started building gear that interfaces through the serial port, I recommend that you use an RS232C to RS422 converter, and design your projects around RS422. RS422 is a multi-drop protocol which will allow you to connect multiple devices to a single serial port.

    As you're planning to use a micro controller, you might consider timing the rotational speed of the rotary encoder. If turned slowly the encoder can be made to increment or decrement the frequency in small steps. If turned fast, the step size can be made larger. This avoids the need for a dual concentic encoder. The push switch can then be used as a swap frequencies, or set frequency function.

    The PIC16F628 is quite capable for this purpose. However, the PIC16F648A is newer, has more memory and (at least in the US) is slightly cheaper. The PIC16F876A is another choice offering more I/O pins.

    LCD character displays are a nice alternative to LEDs. It really depends on what sort of radio stack look you're creating. I've used some white on blue LCDs with nice results. There are some pictures posted on the first page of my site toward the bottom. www.mikesflightdeck.com

  6. #16
    Our new friend needs to reach 10 posts to get to the next flight level
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    Low cost radio

    Hi,
    thx for answers. I see that serial port comm would be Ok from the software side. On the hardware side, a point to point comm is a starting point (or two ).

    I will be using a 16F628 for now. It supports RS232 dircetly. In order to keep it simple for now, I will continue with that. To overcome the port limtation, it is fairly easy to make a RS232 hub with one 16F628, one MAX232 (for PC compability) and let's say 4 connectors for downlink using TTL level signals. Then it all boils down to imlementing a communication protocol (message) with suitable addressing. As I have a bunch of 16F628, I will do this. But I agree that it would be better to have a kind of multidrop.

    I have determined to break the inner parts in two: one "dumb" display card which only holds the 6 digits (multiplexed), and one "COM controller" part with 6 digits, the inputs from the switches/encoders and the serial port interface. The reason for using two parts is
    1) difficult to mount switches on a breadboard - heigth migth be an issue
    2) lot of "dead space" if going for a pcb solution
    3) smaller modules are easier to prototype

    The modules used here should be usable for all parts requiring 6 digits, as we have one intelligent unit (the controller) and one dumb unit. Hopefully, they will be reusable elsewhere in the cockpit.

    Ola
    lnola

  7. #17
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    An Answer to tunatuk posting on previous page

    You CAN use rotary switches to INCREASE as well as DECREASE Nav/Com Radio Frequencies. Just wire a 1 pole 12 position rotary switch as a 1,2,4,8 binary code output. Then all you need to do is to create a PIC code that will read the binary and determine the direction of rotation. That's what Desktop Aviator (http://www.DesktopAviator.com) did with their NAV/COM Radio and their Autipilot Panel.

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