Usb 1.1, 2.0, Otg. What's The Diff?


Kyosys said:
Kimundi said:
I think you could buy a active USB extension cable and just remove the 5 m cord...
You need a hub because it works at usb 2.0 pace and "converts" the 1.1 devices speed, the cord does absolutely nothing

USB is limited to 5 meters, so decent USB extension cables are a self-powered 1 port hub which acts as a repeater for the data signals. As long as the extension cable hub part is 2.0, you can plug 1.1 stuff into it :)

What he seems to be suggesting is that shortening the cable, so it's basically just the box at the end of the cable.

However, you have to be careful. I've seen some such cables where it says "USB 2.0 Compliant Cable", and then when you get the magnifier glass out, you find underneath it says "(Cable is 2.0 compliant. Hub is 1.1/2.0 compatible)". "Compatible" is not "Compliant", and this kind of stuff can bite you in the ass, as they are assuming you will be using it on a PC, where you can usually intermix 1.1 and 2.0 devices.

WD like to do that with USB harddrives too - I have a harddisk which says in big letters on the packaging "USB 2.0 Compliant" and the in really small letters underneath "cable included.". Leaves you confused, is the "cable included" part seperate, or part of the above line? Turned out the drive was only 1.1, so I can only guess the WD marketing dept got involved and were feeling the need to do something in an attempt to retain there jobs.
 
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I know the diff between 1.1 and 2.0, but what's the OTG port I hear you guys talking about? And what restrictions are on the standard USB ports that are on it? Are they not powered?
 
huufarted said:
I know the diff between 1.1 and 2.0, but what's the OTG port I hear you guys talking about? And what restrictions are on the standard USB ports that are on it? Are they not powered?
Good question. Well, the standard USB host port that's the right shape for you to plug stuff into it is fully powered, providing 500 mA at 5 V. However, it doesn't have the hardware to handle USB 1.1-only devices. You can use any fully-compliant USB 2.0 device, like most mass storage devices, but you need a 2.0-compliant hub to plug in USB 1.1 devices.

The OTG port, on the other hand, takes a miniplug. It can act as a host port, but otherwise would be used for transferring files to the SD cards. It requires an adapter to plug devices in, and only supplies 100 mA of current, so it may not be appropriate for some devices.
 
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Basically, OTG is:
USB "On The Go"
Acts as host OR peripheral (i.e., you can connect it to another computer OR a peripheral device)
Supplies power to the bus, but only 100ma
Has only a USB mini-AB plug, requiring a USB A female to USB mini-A male adapter. These can be purchased online for about $10USD. I know, because I've bought one.

EDIT:Changed to include the mini-AB plug
 
Does anyone know if there is a plug which is a One-Port-USB-Hub?
So you just have something ybout the size of a USB plug which allows you to use USB-Devices on the USB port.
Seriously, this is by far the worst thing about the pandora. This way, you HAVE to carry something around to use for example a keyboard. I just don't get why this wasn't worked around on the PCB, the fun in mobile devices shrinks significantly if you have to carry around extra adaptors.
 
jbr said:
Basically, OTG is:
USB "On The Go"
Acts as host OR peripheral (i.e., you can connect it to another computer OR a peripheral device)
Supplies power to the bus, but only 100ma
Has only a USB mini-A plug, requiring a USB A female to USB mini-A male adapter. These can be purchased online for about $10USD. I know, because I've bought one.
The above needs to be corrected: it as a mini-AB (either a mini-A or a mini-B connector can be plugged into it).

Mini-B connectors are rather common, most people have probably never seen a mini-A connector.

If the Pandora had a mini-A connector, you would not be able to plug a mini-B cable into it. They were designed to be mutually exclusive so you could not fry your system by plugging the wrong connector into it.

USB OTG came about later, and since it allowed the device to be either host or peripheral, it needed to be able to have either cable connected to it, hence the mini-AB connector.
 
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And, just like the TV-out, I get confused and slightly frustrated. :p

So, all I need is any USB cable to be between the Pandora and the device? Or must that cable/hub have particular qualities?
 
Whoops, sorry about that. I was thinking about the mini-A in terms of what you need to use it as a host, and I totally forgot to mention the dual function jack.

Also, the most common place (AFAIK) to see a USB OTG port, and indeed a USB mini-A connector, is in the link system between TI-84 and TI-89 calculators. The link cable has two ends, labeled A and B, with very slightly different connectors.

As far as I know, however, the only difference between A and B is that the device hooked up as 'A' supplies the power.
 
I guess I'm confused as to why you can't use a USB 1.1 in the USB 2.0 socket. I never knew there would be an issue since USB 1.1 didn't usually require the voltage that 2.0 could provide.
 
Balzac2m said:
Does anyone know if there is a plug which is a One-Port-USB-Hub?
So you just have something ybout the size of a USB plug which allows you to use USB-Devices on the USB port.
Seriously, this is by far the worst thing about the pandora. This way, you HAVE to carry something around to use for example a keyboard.
I'm guessing that the best bet here would be to use an adapter as jbr describes (I'd imagine that they're little different in shape or size from something like this), and use the "OTG" port, or, if you're using a device which is wired anyway, use one of those tiny-sized four port hubs and simply leave it hooked up to the end of the peripheral's cable, maybe...

jbr said:
Has only a USB mini-AB plug, requiring a USB A female to USB mini-A male adapter. These can be purchased online for about $10USD. I know, because I've bought one.
I hope you don't mind me asking, but where did you get that adapter from? I've been trying to see if I could find one (from a place that can ship to the UK, with any luck :)), but I haven't had any luck so far.
 
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huufarted said:
I guess I'm confused as to why you can't use a USB 1.1 in the USB 2.0 socket. I never knew there would be an issue since USB 1.1 didn't usually require the voltage that 2.0 could provide.
First, you should not try to distinguish the two types by USB 1.1 vs USB 2.0. If you do, you will get suckered into buying devices that claim to be USB 2.0 devices, but only work at USB Full Speed.

There are three types of devices: USB low speed at 1.2 Mb/sec, USB Full Speed at 12 Mb/sec, and USB High Speed at 480 Mb/sec. (Those numbers are Mega BITS/second). The confusion comes from the fact that USB 2.0 is supposed to support all three speeds, so manufacturers can claim that a USB low speed device is USB 2.0.

USB 1.1 used LVTTL signaling. That is about 3.3 V for a high, and 0V for a low. They also use a pseudo differential signaling. It is pseudo differential because the specification requires the use of single ended highs and single ended lows (both sides of the differential pair both high, or both low at the same time).

In order to increase the bandwidth, USB 2.0 uses something very close to LVDS signaling (current source drivers with much lower voltage). In this mode, USB operates fully differentially. In order to maintain compatibility with USB 1.1 devices, USB High Speed devices initially communicate using USB Full Speed, until they can negotiate the switch to High Speed.

In order to deal with these two modes of operation, most systems have a separate state machine (expensive in silicon real estate) to handle each mode of operation.

My understanding of the Pandora is that the hardware chosen has an abbreviated state machine to handle that minor bit of Full Speed operation before switching to High Speed, so it can't handle normal full speed operations. My guess is that this port was intended to be hard wired to a USB hub which would automatically translate the low speed and full speed transactions into high speed transactions (a requirement of any high speed USB hub).

And yes, I agree that this is a significant flaw in the Pandora. But I ordered one anyway.

Prometheus said:
Balzac2m said:
Does anyone know if there is a plug which is a One-Port-USB-Hub?
So you just have something ybout the size of a USB plug which allows you to use USB-Devices on the USB port.
Seriously, this is by far the worst thing about the pandora. This way, you HAVE to carry something around to use for example a keyboard.
I'm guessing that the best bet here would be to use an adapter as jbr describes (I'd imagine that they're little different in shape or size from something like this), and use the "OTG" port, or, if you're using a device which is wired anyway, use one of those tiny-sized four port hubs and simply leave it hooked up to the end of the peripheral's cable, maybe...

jbr said:
Has only a USB mini-AB plug, requiring a USB A female to USB mini-A male adapter. These can be purchased online for about $10USD. I know, because I've bought one.
I hope you don't mind me asking, but where did you get that adapter from? I've been trying to see if I could find one (from a place that can ship to the UK, with any luck :)), but I haven't had any luck so far.


You might try looking for a mini-A to mini-B cable. This might be easier to find as it is a requirement for USB OTG devices. This would work if the device you wish to plug in has a detachable cable.
 
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Been thinking about this myself :)

To turn the mini-A on your pandora into standard usb A (which only supports usb 2.0 devices remember)

this looks like it will work

this

You can then connect a standard usb hub to this and then usb 1.1 devices (joypad?) to the hub.

Connecting single usb 2.0 devices directly with a standard mini-B connector (external hdd, etc) you could use something like this

this
 
javaJake said:
And, just like the TV-out, I get confused and slightly frustrated. :p

So, all I need is any USB cable to be between the Pandora and the device? Or must that cable/hub have particular qualities?
This is why it was a bad idea not to solve this in the design of the Pandora. It is incredibly confusing to non-technical people. (even to technical people who are not familiar with USB).

Problem devices:
Mice
Keyboards
GPS devices
Really old flash drives.
any USB device that does not have the USB HIGH SPEED logo on it.

These devices can not be connected directly to the USB A connector on the Pandora, they can only be used on that connector if a HIGH SPEED USB hub is connected between the device and the Pandora to translate the USB low speed, and USB Full Speed transactions into USB High Speed transactions.

A USB A male to USB A female cable WILL NOT WORK as a hub.

An extension cable that has a hub in it to allow it to extend USB beyond its 5 meter maximum length will work for some but not all devices because it will only allow devices to use 100 mA.

An unpowered hub is only allowed 2 ports, and each port on an unpowered hub is only allowed 100 mA. So an unpowered USB hub will work just as well as using a mini-A to A adapter on the USB OTG port.

The ONLY way that some devices (those that require more than 100 mA, and do not work at High Speed) will work on the Pandora is if you use a POWERED (meaning it has its own power supply (wall wart, or battery pack)) hub.
 
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DAP said:
This is why it was a bad idea not to solve this in the design of the Pandora. It is incredibly confusing to non-technical people. (even to technical people who are not familiar with USB).

Problem devices:
Mice
Keyboards
GPS devices
Really old flash drives.
any USB device that does not have the USB HIGH SPEED logo on it.

These devices can not be connected directly to the USB A connector on the Pandora, they can only be used on that connector if a HIGH SPEED USB hub is connected between the device and the Pandora to translate the USB low speed, and USB Full Speed transactions into USB High Speed transactions.

A USB A male to USB A female cable WILL NOT WORK as a hub.


An extension cable that has a hub in it to allow it to extend USB beyond its 5 meter maximum length will work for some but not all devices because it will only allow devices to use 100 mA.

An unpowered hub is only allowed 2 ports, and each port on an unpowered hub is only allowed 100 mA. So an unpowered USB hub will work just as well as using a mini-A to A adapter on the USB OTG port.

The ONLY way that some devices (those that require more than 100 mA, and do not work at High Speed) will work on the Pandora is if you use a POWERED (meaning it has its own power supply (wall wart, or battery pack)) hub.
Excellent explanation. Wiki content right there. Thanks a bunch! :D
 
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DAP said:
This is why it was a bad idea not to solve this in the design of the Pandora. It is incredibly confusing to non-technical people. (even to technical people who are not familiar with USB).

The problem lies with the USB support built into the OMAP chip. There was no way to "solve" it, only to make the best of an unfortunate situation.

Merged with nearly identical thread.
 
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Chip said:
The problem lies with the USB support built into the OMAP chip. There was no way to "solve" it, only to make the best of an unfortunate situation.
<picky>Well, they could have slapped a GL850A on the motherboard :)</picky>
 
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Squidge said:
Chip said:
The problem lies with the USB support built into the OMAP chip. There was no way to "solve" it, only to make the best of an unfortunate situation.
<picky>Well, they could have slapped a GL850A on the motherboard :)</picky>


Yeah, great idea, but that's yet another item that would bump the cost up even further.
 
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