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My Omega 2/2+ dock\new

  • Hi everyone,

    I want to present my project: it's a small dock (same size as the mini dock and the omega) for the Onion Omega 2 and 2+.


    I needed the smallest dock i could do, that featured:

    • Ethernet
    • Type A USB host
    • Micro USB for power

    Here's what i came up with, i called it dock\new.


    It has an onboard linear voltage regulation (i didn't bother going with a switching one for such low power), magnetics integrated in the RJ45 connector to save space, USB host ESD protection (diode array), USB host PTC fuse.

    On the left side there is the RJ45 connector and nothing on the back side of the board, so that you can easily access the MicroSD card on the Omega 2+.
    On the right side (the antenna side of the omega) you have the USB type A connector, facing outwards, and the microusb connector for power, facing inwards.

    The first version, which you see in the photos, had some issues with the ethernet. Currently i've released v1.0 that solves all the issues, adds a led to check power and, making a better use of the space, the RJ45 connector doesn't protrude anymore. I haven't ordered the v1.0 PCBs yet, but the circuit is tested.

    I've chosen 0805 passives, 1206 ptc fuse, big smd electrolitic caps, a SOT223 (the classic 1117) for power regulation and a SOT23-6 for usb host protection, so it can all be easily handsoldered with just a plain soldering iron. Probably the hardest part to handsolder is the SOT23-6 but it's easily doable by hand.

    The components and board cost for the prototype it's arround 10 to 15ā‚¬ per board. It would go down with bigger volumes.

    The project is open source (CC-BY-SA 4.0).
    KiCad schematics, board layout and the other files are available on the github repo.

    The schematic of v1.0 is also posted here for convenience:

    I really hope you like it!
    If anyone has some suggestions please comment!

  • Great work!
    Just a comment, if I may. From what I know with Omega2 and Ethernet, the ETH_PWR signal should actually be disconnected (central taps of the magnetics just grounded through the 1u capacitor). Have you tested it as on the schematics? Did it work?

  • @Alfonso-Blanco said in Omega 2/2+ dock\new:

    Great work!

    Thank you! šŸ™‚

    Just a comment, if I may. From what I know with Omega2 and Ethernet, the ETH_PWR signal should actually be disconnected (central taps of the magnetics just grounded through the 1u capacitor). Have you tested it as on the schematics? Did it work?

    That's the tricky part, where i've had most of the issues. In the original schematic from omega, the NEW_POW net is connected to pin 25 (the VOUT pin in the pinouts). In my first desing i thought that tieing the central taps and the VOUT pin to 3.3v can make the things simpler. Turns out that the ethernet doesn't work at all if you do that.

    So i've bodged in some wires and cut some tracks, to test it with the original ethernet expansion schematic and it works fine. I will also test it with the center taps connected only to the cap.

    The other issue i've had is that normally J1 and J2 from the ethernet cable are connected to the TX pair, on the omega 2/2+ they are connected to the RX pair. I've tested both configurations (J1-J2 to TX and J3-J6 to RX, and vice versa) and both work fine, but i don't know if the omega has its own auto MDI-X or it's just my network equipment.

    Anyway in the pinouts the purpose of the NEW_POW/VOUT pin is not clear.
    The design i published is what i'm using right now, tested and working.

    Maybe we should ask someone from the Onion hardware team to clarify the NET_POW usage and the TX/RX ethernet pairs connections

  • @Valerio-Backslashnew Perfect reply. Those are exactly the same issues Im coming across.

  • In Omega2, although that PIN is labeled as Ether_Power, there is no internal connection (N/C), so it is as good as "does not connect" to anything or "just floating".

  • @ccs-hello So it's unnecessary to connect the center taps with VOUT pin? It's enough to connect it to the capacitor?

    BTW i changed username so it might appear that i'm another user (in fact i can no longer edit the posts above), but i'm still Valerio Backslashnew šŸ˜‚šŸ˜‚šŸ˜‚

  • looks like a nice board. i'm wondering if you have any plans to have some fabrication[pcb] firm make a batch and you sell them or at least offer for sale through the pcb firm.?

  • @Douglas-Kryder i have some spare boards from the v0.9 prototype run. I can consider giving out those boards to recover the prototyping costs.(the v0.9 boards need some track cut and some wire bodge)
    Maybe i can also make a small batch of boards with all the components soldered so that who can't solder, can still get his own.
    How about that?

  • @valerionew said in My Omega 2/2+ dock\new:

    So it's unnecessary to connect the center taps with VOUT pin? It's enough to connect it to the capacitor?

    Yes and yes.

  • @valerionew hi. if you get the bugs worked out of the board and either you have them for sale or the pcb place has them for order i would be interested in at least 1 and maybe a couple more depending on cost or, if you can make a kit with all the components un-soldered that would save the cost of getting all the pieces i don't have available here that would be good. if all you plan to offer is soldered units then 1 of those if you can keep the cost relatively low.

  • pros: very nice! i need 1-3 of them.
    cons: hard to use GPIO without soldering.

  • @Douglas-Kryder and @Andrii-Petrenko if you want multiple boards i can recommend you to get them from OSHPark. They've done a really good job with v0.9, plus their boards are purple like the omega. I've already uploaded the board here. I have to remember you that the v1.0 is not tested yet, so proceed at your own risk. The same circuit with bodges works on v0.9 but you never know what can go wrong.
    Also, i'm trying to contact some chinese manufacturers to get their best price for the RJ45 connector with magnetics, which is the most expensive part in the project. I'll let you know if i can get their attention and an offer for such low volume.

    @Andrii-Petrenko for the lack of IOs, this wasn't my first intention with this project, but i think you can try to squeeze in some SMD .1" angled headers on the back side of the ethernet connector. Something like this
    2x08 SMD angled headers
    With the omega 2 you should be able to place 2x8 pins. With 3.3v and GND, that's 14 GPIOs.
    On the omega 2+ there is the SD card there, so unless you somehow raise the two omega strip connectors (there is some extra pin lenght on the strips i used), you will be able to place only 1 row, giving you 6 GPIOs available, plus 3.3v and GND.

  • And, of course, thank you to the onion team for featuring my project into the newsletter!
    I'm really glad you like it!

  • It's great that this just came to my attention, because I've been "building" a harness that has a micro-usb in for power, an LD1117 to step it down, and then has the USB host port for a camera to hook up. I found a 10cm (4") micro-usb female cable (so a phone charging cord would plug into it) and cut the end off and soldered it to the LD1117. The 5v and ground from it are also soldered to another 10cm cable, this one a USB-A female cable that I also chopped the end off of. I'm waiting for 2mm female jumpers to arrive before I can hook up the ground, 3.3V, USB+ and USB-. Your solution is so much cleaner and smaller!

    And, looking at your schematic, I see you have TTL between the usb +/- and the onion...I thought I read some things saying that it would hurt do that, but also isn't necessary. I take it, that I'm wrong about that, and need the TTL?

  • A couple of noob questions around crafting such an elegant board: how/where to get the board (oh, I see you answered that, OSH Park); and how to get all the smd stuff soldered to it.

    The only thing I've seen about smd says that you have to get your spouse's clearance to bake the stuff in the oven. Is there a provider like OSH Park that will do it? Will OSH Park? If not, can you point out any good info...getting solder onto the board before the baking seems...problematic for us lesser hobbyists.

    I don't think that you manually soldered the board in the pictures, so how did you get that done? The baking option?

    At any rate, if you do offer these for sale, I'll take 2.

  • @Me-Too I've just replied to an issue on GihHub with (i hope) all the answers you need. I don't know if that one is also from you or not.
    Please check it out here: https://github.com/5N44P/omega-dock-new/issues/10
    If i've not answered all your question, please ask! Here or on GitHub.

  • @Me-Too i would add to the discussion that the boards come in 3-packs for ~ $9US. it might be easier if you use solder paste for some of the components, put a adequate amount on the pad and place the piece then use either a soldering iron or hot air or in a pinch put it into a heated oven i suppose (never done it) if you do the oven you might want to mount all pieces first. otherwise you will be reheating the solder multiple times on some components and i'm not sure if that is best thing to do. my order is waiting on osh park getting a full panel so if you order soon it might help us all get the boards quicker. šŸ™‚

  • Guys-you're great!

    Yes, @valerionew, you're right that I asked in both places. I created a gist before I found this, and decided it might be useful to have it here, too. Thank you so much for the answer and listing the equipment you have! I doubt I'll buy what you have (sometimes I'm cheap about the wrong things, but I won't use these very much), but it's great to see the actual equipment to see if what I have might suffice.

    My fear of SMD is due to previous experience where the contacts and pads were completely obscured by the part. That made baking (which I read an article once about doing smd that way) or possibly hot-air, but only sometimes on the air.

    @Douglas-Kryder Thanks to you too...the solder paste seems like a great, and easier idea, even though I've never used it. I'm glad it's 3 packs, so I can still get 2 if I screw up the first attempt!

    Oh, and I'm placing the order now, so maybe that will help get them quicker.


  • @Allnight , forgot to mention that there are many videos on youtube that show methods of smd soldering.

  • By the way i checked the ethernet speed with iperf. Seems good to me. (94.4Mbit/s up and down, in case the image doesn't work)
    I'm using a 0.1uF instead of 1uF capacitor to ground the center tap of the transformer, but i don't think that's significant. If you happen to have a 0.1uF 0805 capacitor instead of 1uF, don't bother buying a 1uF one.


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