TM-710A Keyboard Adapter Design

Interest during the last few months is very sparse on the TM-710A Keyboard adapter.  I haven’t’ put much work into it since I’ve found other options.   I do not plan on doing any more kits for this board at this time. This is a option for anyone that did not complete an initial build.

The concept used on the board is to drive the normal mic with a AVR chip and emulate the mic on the TM-710 board which is controlled by the AVR.  Software will have to be completed to come up with something useful and this design may not be perfect.  I have used this board and the previous OSW board in my mobile setup for a long time without any issues but have switched to using a SSD based PC.

If you have any suggestions, changes, or bugs; please submit those back.


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12 Replies to “TM-710A Keyboard Adapter Design”

  1. Are you just randomly sprinking components on the PCBs and then hitting the autoroute button? Yikes. For instance, P2. Why not place it under U4 so the routes didn’t have to run around it??? The 4 resistors to the lower right of U4 should have been moved upwards, rotated and placed so that signals don’t have to route under the resistors. Try to minimize trace length. If you are stuck running with the autorouter, at least run it a couple of times, moving components around to find the best path if you aren’t able to visualize everything up front.

    Where the heck are the bypass caps for the chips? They aren’t optional and should be placed close to the power pins of the chips. Are they really just all piled up at the regulator???? Wow….

    Your positive power signal should be star-routed, not just lazily running around the PCB randomly. Doing it as a star means that noise from some chips won’t affect others. That’s important when you are doing single or 2 layer boards and can’t count on an inner power plane.

  2. As with all prototype work, it is a rapid design. Also with this particular project its more proof of concept than high production board. Breadboard, place, autoroute, and prototype run. Also this isn’t a high speed circuit design. I’ve used this for months in my application without any issues.

  3. Well, fair enough. The changes that I’m suggesting don’t take much time though so its still possible to rapid prototype while taking a little more care to make things better.

    At some point (whether it is this board or another) it will cause circuits to fail in random ways causing much debugging pain. My concern is that by putting these designs out on the web at large without the disclaimer that you’ve cut corners in the placement and layout that other people may take this as an example of expert level work and follow suit.

    Obviously everyone has to start somewhere. My first boards were ugly also. While my comments were harsh (and likely more rude than was necessary), my intent was that your future designs will improve.

  4. In prior post related to the TM-710A it was disclosed that its all prototype stuff subject to error etc etc. Since I have since came up with another solution to the problem I wanted to go ahead and put up the work for others. The adapter could be refined a great deal, but even at this revision it works, at least for me. If I were selling a tested kit I’d revisit the board in its entirety. I really just wanted to first see if I could do it, then a few (very few) people asked to build along with me. Some completed it some didn’t. Anyways its great to get some feedback.

  5. Unfamiliar. Does the 710 keep control of the TNC when interfacing with Xastir or does Xastir take direct control of everything? How much do you need to reconfigure the 710 settings when using Xastir?

  6. Heh, yeah, that article is why I was asking if Xastir worked with the 710 better. APRSISCE looks like it would work great for just monitoring and displaying incoming data, but won’t work seamlessly if you want to message. Not really what I’m looking for. I do plan to use my netbook to monitor just like this article, but it looks like it’s not really worth it to use the netbook to enter messages.

    Well, if the hand mic works for entering messages, that will probably be the way I go.

    Disclaimer: I won’t receive my 710 until Thursday so some of my comments might come off as clueless to an experienced 710 owner 😉 Damn UPS is too slow.

  7. I think most users of the 710 would prefer to type messages via a real keyboard. The best solution is to just use xastir to send and receive messages for me. I developed the board just to do it and for those that wanted to just have a keyboard that simulated the microphone input.

    From a practical standpoint I found it much easier to just setup a dedicated notebook vs using the 710 interface with a keyboard. Since then I’ve moved to digital modes and I’ve been using a terminal interface to TICKETS cad for my ARES work.

    When your 710 arrives, if you would like to have a PS2 keyboard inline, the 710 adapter board I have here is what you would need. You should be able to put one together after etching or ordering a board in under an hour.

  8. It is not clear if you got this sending key-press data. (comments are on the layout, TNC and xastir). The serial protocol is quite unconventional. Looking at the schematic, the two 4017s scan the keypad matrix and give a string of something like, I think, 64 pulses (possibly a few more) where one bit out of each nibble is missing (0) for the pressed button where all the others are “1”. No pulses are there when no key is pressed. The clock, from the radio, is on the same line that the pulses come back to the radio. Does this sound correct?

  9. Yes I can decode all the mic data. I’m not sure what you are looking at on the data line. I actually built no less than 3 different prototypes that interfaced with the TM710 at different levels of operation. Once was just a board to convert signals using a MCU, another was a full USB keyboard that still supported mic passthru, then finally a PS/2 low power combo that took power from the mic to allow a PS/2 keyboard to be used along with the mic.

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