I'm not saying that is 100% exact nor that I have a very accurate meter.Jim Manley wrote:Something is seriously wrong with these numbers.
From everything I've experienced and others have reported, there's no way a Pi can run on 4.2 volts at the supply input - none, nada, zip. Where/how was this measured?
Note that yellow and shield is GND and the two blacks are +5V. Try connecting the USB data (+/-) and GND to a male USB and connect it to a regular PC. It should work like a regular keyboard/mouse.masterofstuff124 wrote:I first had the black and yellow wire each going to power and the red and brown going to data. I would get the errors posted above. Now I have both Blacks and the yellow and the shield going to power. And the red and brown both going to usb. Same errors as above.
Was the one in question an Atrix or Droid model? Seems most people have been playing with the Atrix model ones?masterofstuff124 wrote:does not work when connected to my pc. Im not so sure it ever would. as i tried hooking my android phone via the otg adapter and never got the keyboard/mouspad to work.
OK, I missed what configuration was being measured, as I had read the earlier post mentioning the board component stripping and didn't correlate the two posts.Lob0426 wrote:The SoC will run on 3.3v. The USB is the item that needs 5v. @godFather89 replaced the linear with a switching regulator on his RasPi. The switching regulator will turn out a steady 3.3v with a 4.2v input.
The A model runs without the LAN9512. They jumper over the PCB LAN chip area so it passes directly to the single USB port. with the Lapdock having its own hub you would only need the data lines to USB, no power output. You will still need to bring power into the RasPi from the Lapdock. You end up using your one port to get two ports on the Lapdock. But you have a keyboard and pointing device already.it would make for a very minimalist install. I am sure the Lapdock would be very popular with the A model and a wireless dongle. If all you intend to use is the Lapdock you do not need the analog sound or RCA video jacks. Putting in a switching regulator would extend battery life. You could run the USB PiPass if you wanted to keep the second USB working. That is what I plan to do.Jim Manley wrote:OK, I missed what configuration was being measured, as I had read the earlier post mentioning the board component stripping and didn't correlate the two posts.Lob0426 wrote:The SoC will run on 3.3v. The USB is the item that needs 5v. @godFather89 replaced the linear with a switching regulator on his RasPi. The switching regulator will turn out a steady 3.3v with a 4.2v input.
However, while the info is interesting in an intellectual way, I don't see how this is of much use to anyone not willing to tear their board down to eliminate interfaces that virtually everyone needs. You can't even operate it over a network since stripping off the Ethernet/USB controller eliminates the network as well as a USB port. If you were going to try to run it via USB WiFi or wired Ethernet, does the Model B board even have the traces to support a single USB port via the SoC if the controller is stripped off? If you're going to attach even just a USB keyboard, you're going to need the 5 volts, anyway, or are you going to rely on a battery-powered hub to pass the 5 volts back? It's feasible to measure the current draw of things like a keyboard and a mouse and subtract them from the total power draw if you're just interested in the SoC power draw. Are you envisioning running the SoC via battery with no interfaces beyond video and audio outputs?
The low-overhead regulator is a good idea.neggles wrote:... see how long it'll run with a 3F supercap on the 3.3V bus...
I've had my fair share of supercapsplosions XD they get very upset when you don't put a resistor in series to limit charging current (or use a current limited power supply), for one... after all, exposing a capacitor to an unrestricted power source theoretically results in infinity amps for a very short period of time >.>Jim Manley wrote:You're probably aware, but, for those not familiar with supercaps, they can fail quite spectacularly (aka explode violently), especially when shorted or exposed to higher-than-rated voltage, but, sometimes just because of the phase of the moon. They deserve more respect than other components, so, eye protection, encasement, and other precautions are absolutely required when working with them on exposed boards. Be careful you don't short a charged one lying out on a work surface, either. Don't ask how I know more than I want to about this topic
Nice! I might just order one once I know it works. The only potential glitch could be if the cable conductors are on the skimpy side, since we now know that the Pi can draw upwards of 1,000 ma of current, even more depending on what's plugged into the USB ports. Higher current results in a larger voltage drop across the cable, and the Pi is touchy enough about low voltage as it is. At least the cables aren't very long, as that also contributes to voltage drop.Syliss wrote:Was thinking of using this usb cable for power/data. Just cut off one end for data! Anyone tried this cable before?