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I have a device that has a NXP MK66FN1M arm core processor with a black and white display. This device is running FreeRTOS with serial, usb, keypad, display, external FeRAM, wifi, and ethernet.

What methods are available so that from a remote PC I can see just the same as what is on the screen of the device. We would like but not require that buttons presses can happen on the remote PC and transmit to the embedded device.

We have come up with three possible groups of solutions.

  • State machine
    We have a separate program that runs on the PC. There is an assumption that the indicator and PC program start at the same state. As button presses happen they are transmitted to the other device and the state machine changes accordingly.
  • Display commands
    Every time the embedded device issues a command to the display we issue the same command to the remote PC application. This application is a virtual display and re-implements each command.
  • VNC server
    We can use VNC so that end users can use any VNC viewer program to see the indicator.

The state machine method would fail when the devices get out of sync. The VNC server is not doable as far as I can tell b/c I cannot find any freely available libraries and commercial options are to expensive or would require re-implementing things that are already done. VNC would be nice because we would not have a custom application on the PC that we would have to maintain. The end user could use any VNC viewer.

Any ideas?

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If in doubt, pick the simplest, which in this case is, I think, #2.

Specifically, work out the minimum required information the PC needs.

For example, if your display consists of two lines of text, you send two strings to the PC. If your display consists of a number of icons, you could send a bitfield (or equivalent) where each bit indicates if that icon is on or not.

If the PC's output doesn't have to look identical to the real display, then you can take advantage of the fact that you'll be outputting to an app running in a GUI. The embedded device supplies the data, while the app provides the formatting.

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