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Project for the lock-down. Shop project but not machining..

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  • Project for the lock-down. Shop project but not machining..

    An exhibit in our aviation museum.

    Click image for larger version

Name:	shacksmall.jpg
Views:	267
Size:	36.3 KB
ID:	1867290

    The project is to decode hand keyed morse and display it on a screen.

    This is easy with a PC but there are problems stopping and starting the PC by power off/on. An old PC (e.g. XT) might be OK but they seem as scarce as async terminals which would be an alternative.

    Decoding with a Arduino is easy but they cant drive a display while timer interrupts are firing off as required for the decoder.

    So I am looking at a Pi although I am unsure of their timing capabilites.

    I need to take about 100 samples per second for decoding the hand sent morse.

    We have PCs in flight simulators and they are a real pain when opening and closing the museum so I have made 'black boxes' to handle things but they require both mains and hangar light circuit supplies. Lighting circuit only available in the aeradio shack.

    UPS have been voted out!

    Any ideas?

    Thanks
    Last edited by The Artful Bodger; 04-08-2020, 05:44 PM.

  • #2
    If UPS has been ruled out, have you also ruled out batteries? A 3000 mah battery pack will run a Pi B+ for 15 hours or so at idle.

    More seriously, I have a web cam that's being read at over 60 FPS. Chances are that you should be able to watch the i/o lines for state change . A quick search found this link that said 10mHz was the max sample rate.

    https://www.raspberrypi.org/forums/v...c.php?t=128387

    At the end of the project, there is a profound difference between spare parts and left over parts.

    Location: SF East Bay.

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    • #3
      Thanks, yes I am looking at a Pi but it is totally new to me.

      Comment


      • #4
        Sounds wasteful but use each item for the process it is best for - decode with the Arduino and send the output to the Pi for display. Actually as it is a museum and just text you are displaying wouldn't a Creed 7B make a cool display device.

        Comment


        • #5
          Yes a Creed 7B or Teletype Model 15 would be cool, but people would try to rip the paper off and I would be continually called to clear the jams, we have a limited supply of roll paper, I remember what a pain it was to keep TTYs going 50 years ago! But a cool idea otherwise and there is a Model 15 in that wooden case.

          Of course I could send to a dot matrix printer and I even know how to make each character print without waiting for CR or NL, but again paper jams.

          Nonetheless a printer is not yet totally discounted.
          Last edited by The Artful Bodger; 04-08-2020, 08:34 PM.

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          • #6
            Nice AR-88 there. I have one that is waiting restoration.
            IIRC, one of the magazines, maybe Popular Electronics or Radio Electronics, had a stand alone morse to text translator that used a dot matrix LED display. This was maybe in the 1980's. I remember thinking it would have been a cool project to build.

            Comment


            • #7
              John,

              I have not seen you in ten years. Still, that can't be you at the desk.
              Allan Ostling

              Phoenix, Arizona

              Comment


              • #8
                Originally posted by The Artful Bodger View Post
                Yes a Creed 7B or Teletype Model 15 would be cool, but people would try to rip the paper off and I would be continually called to clear the jams, we have a limited supply of roll paper, I remember what a pain it was to keep TTYs going 50 years ago! But a cool idea otherwise and there is a Model 15 in that wooden case.

                Of course I could send to a dot matrix printer and I even know how to make each character print without waiting for CR or NL, but again paper jams.

                Nonetheless a printer is not yet totally discounted.
                Ah, yes. TTYs. At one point I could type on a model 28 (60 wpm model) at 59 wpm as measured by the sergeant grading my papers. Remember, at the end of the line, it's CR-CR-LINEFEED-LTRS. All to give the machine time to get ready for the next character after the new line.

                Good old days? Not really. But I had my own TTY for many years, gave it away about 20 years ago.

                -js
                There are no stupid questions. But there are lots of stupid answers. This is the internet.

                Location: SF Bay Area

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                • #9
                  Originally posted by aostling View Post
                  John,

                  I have not seen you in ten years. Still, that can't be you at the desk.
                  Not me Allan but a dear departed friend of mine.

                  Comment


                  • #10
                    Originally posted by Jim Stewart View Post

                    Ah, yes. TTYs. At one point I could type on a model 28 (60 wpm model) at 59 wpm as measured by the sergeant grading my papers. Remember, at the end of the line, it's CR-CR-LINEFEED-LTRS. All to give the machine time to get ready for the next character after the new line.

                    Good old days? Not really. But I had my own TTY for many years, gave it away about 20 years ago.

                    -js
                    Yeah, those were the days. We used to impress the girls from the typing pool by showing how we could touch type with one hand! A lot of the morse operators had acquired that skill but not me.

                    Comment


                    • #11
                      I really have to wonder just how much you have put into any of the points that you have rejected. Some thought in red below inside your quoted text.



                      Originally posted by The Artful Bodger View Post
                      An exhibit in our aviation museum.

                      Click image for larger version

Name:	shacksmall.jpg
Views:	267
Size:	36.3 KB
ID:	1867290

                      The project is to decode hand keyed morse and display it on a screen.

                      This is easy with a PC but there are problems stopping and starting the PC by power off/on.

                      If you mean that your system must start up/boot up when power is turned on, a quick internet search provided a vast array of hits for "power on reboot". Does that help on this point? I would suspect that the reason for doing this is to recover from a power failure, so just turning the power off should not be a problem when you want to shut down or if there is a power failure.

                      An old PC (e.g. XT) might be OK but they seem as scarce as async terminals which would be an alternative.

                      I suspect you can find older, computers that can run DOS in places like E-Bay. But they may not be so easy to maintain. I went through that nightmare at my last job: there was a sledge hammer party when the last PC-XT was taken off line. I probably swung the hardest.

                      Decoding with a Arduino is easy but they cant drive a display while timer interrupts are firing off as required for the decoder.

                      Just why are interrupts required? Couldn't a simple loop first check the state of the input and then go to a display driving routine? And then back to the start. I know the "real", the "serious", and the "professional" programmers have their favored ways of doing things, but less "real" and less "serious" and less "professional" methods do still work. Just make the loop simple enough, short enough so that it executes in 1/100 second or less. If it takes too much code to update your display, use another device for that: just transmit the decoded text to it.

                      So I am looking at a Pi although I am unsure of their timing capabilites.

                      In what sense is timing a problem? You could probably keep a weighted, running average of the length of the pulses: if it is shorter than the average it is a dot and if it is longer it is a dash.

                      I need to take about 100 samples per second for decoding the hand sent morse.

                      We have PCs in flight simulators and they are a real pain when opening and closing the museum so I have made 'black boxes' to handle things but they require both mains and hangar light circuit supplies. Lighting circuit only available in the aeradio shack.

                      I fail to understand just how you would need to connect to two different power circuits. The mains, as you say, should provide all the power that is needed for the devices. If you are using the light circuit as an indication as to when to shut down and turn it back on, wouldn't a photocell circuit work just as well. Lights go out, the photocell sees that, the box shuts the device down. Lights go on, the photocell sees light, and the device is booted up. My truck and car both use a photocell to know when to activate their headlights. If Detroit can do it, so can you. And from my experience with headlight repairs, you can probably do it a lot less expensively and more far more reliable.

                      UPS have been voted out!

                      I would say take another vote, but I really do not like the idea anyway. Forget UPS.

                      Any ideas?

                      In spite of the fact that I believe that almost any Apple or PC computer could do this, either would be gross overkill. I would think any <$10 PIC device could do it, even the ones that are programmed in machine or assembly code. And if there really are problems having one device do both the decoding and the display, then just use two: one for each function with a simple serial line between them. The type of display you are using would be the factor to look at to determine the device that is driving it.

                      There are vast amounts of on-line help available for all of these devices as well as programs and macros written to do almost anything. All you need to do is find the ones that do what you want and paste them together into one program or one system. Here is just one quick search for "PIC Morse Code Decoder":

                      https://www.bing.com/search?q=PIC+mo...F7C923D88F8592

                      I would bet you could substitute "Arduino" or "Raspberry Pi" or "PicAxe" or any other higher level PIC device in that search and get a similar batch of results.

                      Yup, here's one:

                      https://www.bing.com/images/search?q...8B&FORM=IQFRBA

                      Looks like the first photo in that search shows a PICAxe device doing both functions: decoding and driving a display.


                      Thanks
                      Paul A.
                      SE Texas

                      And if you look REAL close at an analog signal,
                      You will find that it has discrete steps.

                      Comment


                      • #12
                        Paul...

                        Power ON/OFF
                        If we run PCs from the lighting supply turning the lights off when closing the museum kills the PCs but the problem is that just cutting the power is not an 'orderly shutdown'. The orderly shutdown is possible with a UPS but we dont want a UPS. If the PC is not shut down in an orderly manner it will likely complain at restart and require manual attention. There is also a risk of disk corruption (so they say).

                        An old PC such as an XT probably wont mind if the power is interrupted and neither will a disk be corrupted if we are booting from a floppy that is write protected.

                        In the same vein I suspect a 'diskless workstation' may be OK but we dont have one on hand.

                        Interrupts
                        Regular input samples make decoding so much easier and that includes software debouncing. Simple loops may be practical depending on what demands are being made by the display.

                        Lighting and mains supplies
                        A photocell might work but in this case the Aeradio Shack is on the lighting supply.


                        The display
                        We really want the display to be big rather than small or tiny and of course there are plenty of TVs and monitors on hand. The connections options are then HDMI, video and serial (if we can find an async terminal)

                        At this point it looks like Arduino to do the decoding, serial link and Raspberry Pi to produce HDMI to a monitor.


                        Thanks for your comments.

                        Comment


                        • #13
                          I run a small nuc computer with win 10 pro that is booted when the main power to the machine is turned on. It is killed when the machine is turned off. It has never failed to boot correctly and run the software automatically that is configured to open automatically when the computer boots. What you want to do is very easy with a win 10 machine. Unless I am missing your point.
                          Location: The Black Forest in Germany

                          How to become a millionaire: Start out with 10 million and take up machining as a hobby!

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                          • #14
                            Thanks Black Forest, that is encouraging. Does the nuc have a solid state drive?

                            Maybe if I look through the entire stack of surplus PCs etc I might find one that reliably tolerates a forced power off.

                            Comment


                            • #15
                              Originally posted by The Artful Bodger View Post
                              Thanks Black Forest, that is encouraging. Does the nuc have a solid state drive?

                              Maybe if I look through the entire stack of surplus PCs etc I might find one that reliably tolerates a forced power off.
                              I think it does but I will have to check to be sure.
                              Location: The Black Forest in Germany

                              How to become a millionaire: Start out with 10 million and take up machining as a hobby!

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