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Thread: Open source WiFi RS232 Modem

  1. #41

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    Quote Originally Posted by drdanj View Post
    Thanks Tim Those're really awesome bits of advice.
    No worries, glad to help!

    Quote Originally Posted by drdanj View Post
    Beefed up the power and tidied it up where I can - you can't really go any bigger than the pad that you're supplying the voltage to (or taking it from), but I tried to keep the trunks bigger where possible.
    Actually, you can! I don’t know if KiCad has implemented this yet, but most EDA tools will automatically neck down larger traces when they go into smaller pads. For example, if a pad is 20mils wide and I select a 40mil trace, it will start out at 15mils wide, then go up to 20, 25, 30, 35 and finally 40mils over the first 10mils of the trace. If KiCad doesn’t do this automatically you can still do it manually.

    Yes, the final pad size will still be smaller than the trace, but that’s OK. The point is to lower the overall impedance of the trace. (Remember, resistance is a function of Trace Width x Length.) A good example of this is the VIN and SW nets of U1 on my board. The pads of the IC are tiny, but I use hand shaped copper pours that quickly expand in size after they leave the pads to keep the impedance low.

    The trace width of the power net on the Gerbers you just posted should be OK, this is just some advice for future reference.

    Quote Originally Posted by drdanj View Post
    Also added lots more stitching between the layers. I did have a go at shrinking it, but if I want to keep everything on one side it did start getting rather too tight

    Anyway, I think this is better:
    https://gerber-viewer.easyeda.com/sh...-2-3-4-5-6-7-8

    d.
    Yes, that looks much better!
    Last edited by timb; June 24th, 2018 at 05:20 PM.

  2. #42

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    No Kicad doesn't neck down... unless you change the trace with to a larger size after the fact then reset the trace size on that net. Note anywhere that couldn't go up to the new size will remain at the old size.

  3. #43

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    Just a quick note to say that the Schematic/PCB and GERBERs have been updated, as well as the firmware, which now uses all of the RS232 pins the hardware makes available (it ignores DTR for the time being, and just sets DSR as a matter of course, but the facility is there to monitor and manipulate these).

    I'm going to do one more run of boards to test, then will release the hardware properly.

  4. #44

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    Just to say, the version of the hardware now in the repository (2.5) is tested and works. Started filling in the wiki with build information. I've also got a fork of Zimodem here: https://github.com/drdpj/Zimodem - it's more fully featured than the original firmware I was using, but hasn't yet been tweaked to use the actual hardware flow control, it mimics it in software.

  5. #45

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    Have you got it working for "dial in" yet?

    Thanks for building this gadget.

    g.
    Proud owner of 80-0007
    http://www.f15sim.com - The only one of its kind.

  6. #46

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    Yes, both firmwares should allow you to "dial in"

    d.

  7. #47

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    Excellent!

    g.
    Proud owner of 80-0007
    http://www.f15sim.com - The only one of its kind.

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