USB power of 3,3 V

[DeVaIt]

Hi all:

I have a question about USB:
Some time ago, I was wondering why the PSP has 2 cooper "connetions" {they're at both sides of the USB mini-B conector} {By that time, I had 2.7 firmware}. So I tried to see if they had voltage.. and, I was not so surprised by the fact they had, but only 0.24 v {aprox.}..
Few days ago, I read about the PSP usb cam, and made some research about PSP USB capabilities. I found here at the forum that the PSP has no USB Host capabilities {neither On-The-Go could be supported}, so the camera must act like Host.. and should have a power source out of the USB wire..
Just to look about that camera thing, I tried the 3.03 firmware.
After that, I tried again to se if the cooper "connections" had voltage or not.. and.. what was my surprise when I saw that they had 3.3 V {+ at the left and - at the right of the USB con. if you have the screen in front of you}. The voltage is present all the time when in xmb ,but only after pressing the camera icon {after the PSP tries to search for the camera}.
Now my question is... there must be some code at the camera PRXes that should have changed it right?
So, Is there a function to activate the power at that connectors?
Can't it help to make homebrew Host usb devices for the PSP? {I know a little bit about electronics and usb and I think it's possible, maybe with some big effort.. but possible}

Thnx for the attention {and sorry if my english is too bad}, and also, sorry if this are noob questions..

Regards DeVaIt

[gbj1]

If the hardware doesn't support OTG and host mode, it's impossible to connect normal usb accessories directly to the PSP. Host controllers act differently, while OTG can generate host signals to support the connectivity between two accessories. It seems that the only solution would be a accessory which supports OTG may have possibility to interact with the PSP(ie. a photo printer could access memory stick through usb and vice versa).

[DeVaIt]

Hi again:

I am a little confused:

It seems that the only solution would be a accessory which supports OTG may have possibility to interact with the PSP(ie. a photo printer could access memory stick through usb and vice versa).

I would say that somebody here posted that PSP doesn't support USB OTG and can't act like a host..{don't remember who or where exactly} Am I right? if I am, of course it wouldn't be impossible to connect "normal" devices to the PSP, but it's possible to create them from scratch with USB Host capable chips {I know at leats 1 chip that may act like host}.
Apart of that... I would like to obtain some code to activate that power source from the PSP {the one I explain in the first post}. I am so interested on that.. a 3.3V power source is just what I was looking for so I can create a HOST device {if it really doesn't support OTG, because if it dose, that power source would be needed anyways, but the device would be different}.

So I am asking to see.. how can I activate that 3.3v source from code? {if it is possible.. I would say it is, because voltage isn't pressent till you go to the camera option, wich, I supose, loads camera PRXes}
And, Finally does PSP support OTG or not? {I'm confused with this one and your post gbj1}

Thanks for all..
Regards DeVaIt

[Cy-4AH]

If the hardware doesn't support OTG and host mode, it's impossible to connect normal usb accessories directly to the PSP. Host controllers act differently, while OTG can generate host signals to support the connectivity between two accessories. It seems that the only solution would be a accessory which supports OTG may have possibility to interact with the PSP(ie. a photo printer could access memory stick through usb and vice versa).

I will not believe in that! Twisted pair of USB is bi-directional bus. And this two contacts we can use instead standart two power contats for mini-USB. And we must have possibility program this interface and it will work like usb-host.

[gbj1]

look into your linux usb core source code and you'll see how they act.
Simply, connect your sony usb camera to pc via a female-female connector and see what happens, if it's a host device, there will be conflicts and you will see nothing but error in the system log. Otherwise, the camera must be in OTG/client mode.

Seeing is believing, go to www.usb.org and look up for 'host'.

And yes, you can implement a software host protocol stack, and there are serveral commercial ones already, but you really need a 'strong processor' to generate data frames instead of hardware modules. It won't worth the effort than buying a programmed host controller chip.

[gbj1]

I am a little confused

OTG is a supplimental protocol in USB 2.0 standard. It enables a client chip to simulate host controllers. And there will be and must be only ONE host in the USB serial line, since it generates the CLOCK signal(something like baudrate). If someone can make a custom hardware with a host controller and two client port, the host controller MCU is programmed to forward data between two clients, you'll certainly get it working.

[DeVaIt]

OK, thank for the reply..

About the code part (function or something to enable that contacts, so they can be used as a power supply}.. I found at usb.prx the following error text:

[quote]
usbbd ERROR : cannot setup GPIO for USB host power supply : 0x%08x
[/quote]

Made some research and found that it is pressent only from firmware 2.8... Maybe there is actually a function to activate those connector?

Thank for all
Regards DeVaIt

[gbj1]

There must be a power supply management module, since normal usb client devices won't supply power to anyone. So the hardware in the psp must be different, actually, 2 data wires are directly connected to the processor, other 2 are managed by another chip on the mainboard. The function may be a part of device driver, since if you connect a cam to the PSP but not selecting the Camera in the xmb, it won't work at all(NO POWER). But I can't trace the function and locate what the code is, I'm a noob to RISC.