USB connection without a dock
Hm, this is odd. I tried soldering the wires from a USB-Serial converter to the relevant pins on my omega, and it didn't seem to boot (at least, the light didn't come on and as far as I could tell, no wireless network was broadcast). I even tried plugging it into the wall to see if my computer was supplying an insufficient current, but I got no dice there either.
Unfortunately, I don't have a multimeter around to test actual values.
EDIT: I spoke too soon! Turns out I soldered the power wires to the wrong pins >__<
Gian Carlo Salvati
@Fred-Rauch the question was:
"I noticed on the pinout diagram for the omega 2/2+ that the first four pins are the same as a USB pinout (V+, GND, D+, D-), and I was wondering if I could just solder the ends of a stripped USB cable to those pins and use it without any extra gadgetry (notwithstanding a voltage regulator to drop USB's 5V to the 3V3 required), or do I need some sort of TTL converter to make it work?"
I understood: if you connect the USB header pins to a USB connector, it works like the dock?
You answered YES, for it work without any other component or... YES for needing TTL converter?
There is no applicable meaning of a "TTL converter" to USB.
Although VBUS is 5v, USB does not use "TTL" signalling, but rather lower voltage differential signalling.
Some USB capable chip's vendors do recommend series resistors for matching, and some boards have ESD components. But if you look at the published schematics for Mediatek's comparable module for the MT7688, the USB data lines go straight from the connector to the MT7688 pins.
So what is the "final" answer:
you can just solder wires from a regular USB (B) plug to the USB D+, D-, V and Gnd pins on Omega2; then treat the USB pins on Omega2 as a USB host (A) port that can output 5V to the USB plug, and send/receive data on the D pins?
I am thinking of connecting a USB webcam to the Omega2 this way to stream video from the cam via Omega2 WiFi. Hopefully then I will only need a 3.3V PSU for the Omega2 ( maybe LiFE PO4 ) while the cam is powered by the Omega2 USB host port?
@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]
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.
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.
"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.
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.
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.
- 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?
- 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.
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?