Raspberry Pi - a revolution?

[Sirius]

Originally Posted by Cobbydaler

Posting from it now, but suffering from sticky keys on a Logitech K400 keyboard which is supposed to be compatible. Lots of issues with USB power usage it seems...

Been tweeking mine all night

[Cobbydaler]

Originally Posted by Sirius

Been tweeking mine all night

Each to their own, you'll go blind...

[dilli-theclaw]

You get used to it

[Graham M]

Originally Posted by Cobbydaler

Posting from it now, but suffering from sticky keys on a Logitech K400 keyboard which is supposed to be compatible. Lots of issues with USB power usage it seems...

Best bet is to hang a powered USB hub off of it and plug everything into that tbh, the most it can draw from a PC USB port is 500ma (900ma if it's USB 3?) which isn't an awful lot to run a fully functional PC as it is without hanging any peripherals off of it

[Cobbydaler]

Originally Posted by Graham M

Best bet is to hang a powered USB hub off of it and plug everything into that tbh, the most it can draw from a PC USB port is 500ma (900ma if it's USB 3?) which isn't an awful lot to run a fully functional PC as it is without hanging any peripherals off of it

That's the way I've got it set up. Measuring across TP1/TP2 I'm still only getting 4.7V, so I'm wondering if I've got a faulty unit...

[Kymmy]

What's the direct measurement of the PSU/usb you're using to power the Pi?

[Cobbydaler]

Originally Posted by Kymmy

What's the direct measurement of the PSU/usb you're using to power the Pi?

I haven't any probes small enough to measure from the micro USB adapter. I've tried using a powered hub & a Kindle 2A 5V power supply. Even with nothing connected I'm only getting 4.75V.

Link gives position of TP1/TP2 test points:

http://www.raspberrypi.org/wp-conten...011/12/psu.png

[nomadking]

Here is a link from the Raspberry Pi website that might help.
Power from powered USB hub?

[rogerdraig]

i got two of those cheapy hubs so when mine turns up i should at least be able to power it up

[Kymmy]

Originally Posted by Cobbydaler

I haven't any probes small enough to measure from the micro USB adapter. I've tried using a powered hub & a Kindle 2A 5V power supply. Even with nothing connected I'm only getting 4.75V.

Link gives position of TP1/TP2 test points:

http://www.raspberrypi.org/wp-conten...011/12/psu.png

4.7 honestly shouldn't be an issue, 99.9% of usb devices (and also the components on the Pi) are 3.3v or less so the 4.7 should drive a 3.3v regulator fine..

I'm more than likely to suspect the current getting through.. Is the microusb lead supplied with the Pi or a lead for another device? If the latter then how long is it? Just that too long and you'll be limiting the voltage/current to the device.

[Cobbydaler]

Originally Posted by Kymmy

4.7 honestly shouldn't be an issue, 99.9% of usb devices (and also the components on the Pi) are 3.3v or less so the 4.7 should drive a 3.3v regulator fine..

I'm more than likely to suspect the current getting through.. Is the microusb lead supplied with the Pi or a lead for another device? If the latter then how long is it? Just that too long and you'll be limiting the voltage/current to the device.

The lead is a Kindle one, about 1.5m. The Pi people reckon the USB standard is 4.75 - 5.25V which should be obtained across TP1/TP2. I'l see if I've got a shorter micro USB cable somewhere.

[Kymmy]

I'm always dubious about powering non-usb devices from a USB port especially when the USB current output is so limited and the cables involved are not designed for a lot of current anyway. I did have an old HP Jornado PSU (1amp/5v regulated) that I've put aside if I ever do bother getting a Pi as I know that should run it flawlessly.

[Fawkes]

I'm having a problem with my pi too. When it arrived after preparing the SD card and plugging everything in it booted first time. Load LXDE, started Midori to check I had a net connection, all fine. I didn't have much time to tinker, so I shutdown, unplugged and remove the SD.

Next time I came to use it, it would boot.

Tried different powers supplies and reformatted the SD card, every time I try and boot it up I get one of the following:

1. Red LED on and nothing else.
2. Red LED on and faint green LED.
3. Red LED on flashing green LED.
4. Red and green LED’s on but as always not HDMI output.

Reading the wiki suggests a power problem, bad image on the SD card or incompatible SD card but I don't understand:

a) Why it worked once.
b) Why I’m getting inconsistent results.

I don't have the time to work on this now but if anyone has any ideas, I'm all ears.

[Cobbydaler]

Originally Posted by Kymmy

I'm always dubious about powering non-usb devices from a USB port especially when the USB current output is so limited and the cables involved are not designed for a lot of current anyway. I did have an old HP Jornado PSU (1amp/5v regulated) that I've put aside if I ever do bother getting a Pi as I know that should run it flawlessly.

Unless that HP PSU has a micro USB output cable then you're out of luck. I'm not powering mine from a USB port, but from a Kindle PSU (which just happens to have a USB A to USB micro cable)...

[Kymmy]

Originally Posted by Cobbydaler

Unless that HP PSU has a micro USB output cable then you're out of luck. I'm not powering mine from a USB port, but from a Kindle PSU (which just happens to have a USB A to USB micro cable)...

Designed for charging and not powering

In hindsight a microusb for powering such a high current device is a poor option but they've gone for it for simplicity.

It'll be interesting to see what their response is..

As for the Jornado PSU when I selected it the Pi didn't have the microusb at that time but the power supply has a figure of 8 input and a standard DC power socket output that it's easy to make up any lead I want.