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USB connection without a dock

  • @Athar-Mian Yes, the Omega's USB D+, D-, Gnd and 5V+ pins will work to power and work with a USB webcam, but you can't expect the Omega's 5V+ pin to supply that required 5V to the camera if you power the Omega with 3.3V. Either use a 5V USB power source [with a Mini Dock] at the Omega's micro USB socket, or perhaps a DC-DC step-up board to convert the 3.3V source to 5V [for the web cam].
    [edited 2-22-17 to reflect the fact that this thread is about powering an Omega without a dock]

  • @Ken-Conrad

    How about powering the Omega2 directly with 5V and then building the circuit suggested by Omega2 doc. Would that suffice for USB cam powering ?

  • @Athar-Mian Yes, I assume that you are referring to this Onion document for powering without a dock. This will work for you, but you must do the wiring to provide clean stable power to the Omega ... The others who have had problems used a power source that didn't supply a reliable 350- 500mA at 5V, wires that were too thin and/or too long or maybe had some other cause of electrical spikes, for which the filtering caps will clean-up and stabilize the power. If you have incomplete boot or wifi connecting problems then review those posts to improve your wiring and fix.

    Obviously you will also need sufficient extra power to satisfy the power required by the USB camera. Depending on the electronics of that unit, you may want additional caps to isolate it from the Omega ... Good luck. I believe this is an appropriate and good use of the Omegas.

  • @Ken-Conrad

    Thanks for the details.

    I didn't see a description of filtering caps from your link, but remember mention of two capacitors 10-100uF and 0.1uF from a 3.3V ESP8266 tut here:


    So what isolating capacitor do I need use for the USB cam when drawing power from the Omega2?

  • @Athar-Mian For the best power supply caps I would start with what the regulator mfger recommends on their datasheet. The ones you listed could be a good start. ccs hello has a good idea here to use yet larger caps, which help with a possible sag in volts caused by the Wifi chip turning on.

    Regarding how to isolate or minimize electrical noise from your UBS camera ... if you have a problem then first check your USB cabling, commercial USB cables are well shielded, etc. Direct wiring the USB should work but who knows until you try it. If you see a problem, maybe you just need a ferrite bead or then try some small caps. Here is an Intel paper on good USB practices. They mostly address radiated EMF issues but also cover line noise and recommend the use of various caps.

  • @Ken-Conrad

    "Either use a 5V USB power source at the Omega's micro USB socket,.."

    Ahhh, I just remembered this. Where is the Omega2 micro USB socket? Is it directly on the Omega2 itself, since otherwise it defeats the purpose? And is it OTG too?

    Onion folks mostly just mix up the chip and the dock functions.

  • @Athar-Mian There is no USB-socket of any kind, whatsoever, on the Omega2.

  • @WereCatf This is true. I edited my reply from 2 days ago to reflect this. The bare Omega has no USB socket - the USB signals D+ and D- are on several Omega pins. In a roundabout way I was writing that there isn't a 5V source on the Omega and it must be provided for the host USB connection tothe web cam.

    In hindsight, for what Athar wants to do I would recommend getting a Mini Dock.

  • @Athar-Mian said in USB connection without a dock:


    Where is the Omega2 micro USB socket? Is it directly on the Omega2 itself, since otherwise it defeats the purpose? And is it OTG too?

    Top of my list for Omega 3 if we ever get that far.

  • @Ken-Conrad @WereCatf

    Well you could still go the route of 5 to 3.3V PSU set up, use same 5V source to directly power USB cam via its USB power pins, do some soldering etc.

    But overall the $5 Omega2 figure is as much hype as for the RPi0 which is still not generally available ! 5V tolerance ( as for ESP) or 5V external ( with onboard 3.3V conversion) OTG USB receptacle would really have helped, but ... both RPi and Omega2 want to sell expensive accessories.

    The other interesting board I looked at was OrangePi Zero, plus other OPis. But the WiFi driver on OPi0 isn't available owing to the obscure XR819 wifi chip instead of the standard Realtek ones. The BoM comes to $20 if you include memory, casing, PSU and misc.

    Meanwhile Android Boxes fully loaded, very hackable, are down to $24-25 already ! Unless you really want single purpose boards like for $5 Sonoff WiFi controllers featuring ESP8266 or USB cam WiFi webstreaming only.

    1. A wild thought:

    What if Omega2 USB pins could be pre-programmed into slave mode (from default host mode), and a USB plug attached could receive ( not output) power to the USB 5V and Gnd?

    Would this fry the Omega2, or somehow help power the board from a USB hub or USB power adapter?

    1. So from what I gather, for the USB pinout on the Omega2 board, the way for power out is to attach a 5V supply to the USB power pins, for a regular host USB ( A) port function?

    I wonder, with the 3.3 V injection onto the regular 3.3 V power pins as recommended by Onion ( power without dock), what is the voltage/ max current on the USB 5V/Gnd pins?

  • @Athar-Mian Ok, on the bare Omega there isn't a 5V USB anything pin. The Omega is a 3V3 unit. Yes, the docks have USB ports that are 5V compliant, ie on the micro USB connector 5V in and 5V out on the USB-A (old standard size) connector. The docks have a power regulator to step down the USB 5V to 3.3V for the Omegas. Maybe also the TTL RX0 serial to 3.3V, but I can't check as something with Onion's schematic pdfs is broken ....

    I believe the 5V line on the docks is a pass-through, so the maximum current on the USB 5V output is whatever your USB power supply outputs and the USB cable, circuit, wires etc will carry. The specs for USB 2.0 maximum current load is 500mA at 5V.

  • What if Omega2 USB pins could be pre-programmed into slave mode

    They can't be. The SoC has only USB host capability, not USB device capability. This goes back to its heritage as a wifi router; being able to plug in a USB stick for NAS or a GSM modem for uplink is seen as a feature, being able to be a USB peripheral to a computer is not.

    And indeed as already mentioned there's no support for 5v supply on the module itself, only on some of the carriers/docks.

  • A bit confusing....

    So what are the 5V/ Gnd USB pins on the Omega2 pinout diagram?

    If you connect 5V/ Gnd PSU to such pins, can you think of the USB pins, 5V, Gnd, D+ and D- as the 4 pins needed for a host USB ( A) port that can also output 5 V much as a regular host USB port can?

  • @Athar-Mian Which pinout diagram are you looking at? Not the diagram at the top of this thread .... which has VIN and VOUT at 3.3V.

  • @Ken-Conrad

    You are right ! Just confused myself.

    So the Omega2 itself doesn't have a full USB A port, just the serial data pins.

    If you want a "full" USB A port, you will have to supply 5V power externally to any USB A plug then.


    On the Ethernet pins side then, will you need a full Ethernet adapter, or is there a cheaper magnetics only module available to have a "full" fast Ethernet connection on the Omega2 itself?

  • @Athar-Mian In theory you could get something like the sparkfun magjack breakout and hook it up with appropriate bias resistors, but unless you fully understand what would be involved it's probably better to go with the offered solution.

  • @Athar-Mian Have you considered this $4 solution - a Chinese USB hub and RJ45 adapter Haven't tried one yet - I see many ebay vendors who want to sell you one, so good chance it works. Here is a teardown review of a similar unit.

  • A USB Ethernet adapter might hopefully be supported by Linux (though not necessarily the Linux install on an Omega2), but unless it is also supported by U-Boot (definitely not in stock, an open question for a custom build) it won't be useful for reinstalling a stock system.

    In short, USB Ethernet has potential, but support of the specific device has to be considered - it is very different from using the MT7688's built-in wired ethernet support.

  • Interesting info...This Omega2 has a lot of quirks for the $5 advertised.

    So a 3rd party Ethernet adapter (i.e., except via the very expensive dock) is not a solution.

    So what is this MT7688 built in wired Ethernet support? Somewhere it says the MT has either 1 FE PHY or a 5 port Etherswitch.

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