Electronics > Open Source Hardware

Advice on a custom USB device

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xylo04:
Hi folks! I'm a software engineer by day and a radio amateur, but I dabble in electronics. I'm working on a OSHW project right now which is basically meant to cram several USB devices into one.

The project is published at https://github.com/k0swe/tx500-data-interface.

To interface a ham radio with a computer for digital modes, you generally need two things:

* a serial UART for controlling frequency, mode, transmit/receive, etc, and
* a duplex audio signal for received and transmitted digital data (very similar to a modem).Right now I accomplish this with an FTDI cable and a cheap USB sound card plugged into a hub. I want to make a rugged device that has a USB hub controller, UART and audio chip integrated on one PCB. The closest consumer device to compare this to is the Yaesu SCU-17.

I have a design started in KiCad, but this is only my second custom PCB, and it's the first design I've done with ICs and USB buses. I'm eager to get advice on anything that can be improved, but I have a couple of specific concerns:

* Are my uses of power regulation, decoupling caps, signal filtering, etc appropriate? I followed the application notes for my hub controller and UART, but I'm not an EE and don't actually know what I'm doing.
* The audio chip I'm using, the Cmedia HS-100, doesn't have application notes in its datasheet. I currently have minimal supporting circuitry around it. Do I need to add anything obvious? There's some debate in the amateur radio community in general about adding transformers to audio lines like this.
If it helps, I'm trying to optimize for simplicity, small size and ruggedness. This is meant to be in use near RF, but right now I'm only targeting low power operation (QRP), which is 10 W or less of transmitted RF. This is not a consumer device, so I'm currently dispensing with overcurrent and ESD protection. Let me know if I'm going to regret that!

teksturi:
Usually it helps if you give us pdf or jpg straight to this site. People are lazy and do not bother to open someone else project files especially when they do not even know if they are interested. This way you will get more input.  :)

I look your schematic a little bit, but it was too hard to check because it was 6 pages. This would probably fit one A4. That will make it more readable. You can still split one A4 to sections and write headers to thous. Of course this is little bit personal preference but I think no one puts just one usb connector to one A4 page.

xylo04:
Thanks for the meta-advice. Bad habits from programming. :)

I've restructured the schematic and attached it here. I couldn't quite fit everything on one page, but it's down to two.

teksturi:

--- Quote from: xylo04 on March 18, 2021, 12:32:04 pm ---Thanks for the meta-advice. Bad habits from programming. :)

I've restructured the schematic and attached it here. I couldn't quite fit everything on one page, but it's down to two.

--- End quote ---

I try it and it will fit. How does this look? I still leave it upto you if you wanna do this. But still very good start   :-+

xylo04:
Thank you, that looks very good!

Any advice on structural changes?

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