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iRulu 10.1" Model AX105 with Android 4.2

OTG vs. Standard USB Cables

UPDATE "TIDBIT" (to be integrated into the main text of this page at some point in the future): from How to make USB OTG cable--ok, here's something I didn't know / notice before--the standard size USB (type A, male and female) connector has 4 pins, the micro USB (is it a type A also?) has 5 pins, so, duh, there is no connection to the non-existent pin 4 on the full size end. For an OTG, pin 4 on the big end is connected to pins 4 and 5 on the micro end, for a non-OTG cable, the connection to the micro end is only to pin 4.

Original Text:

One of the cables that comes with the iRulu AX105 is known as an OTG (On The Go) cable. In my early reading about an OTG cable, it sounded like the OTG cable was specifically intended to connect between two USB devices and have one serve as a host to the other. Further, if both devices have hosting capabilities, which is the host can be determined by which end of the cable is plugged into which device (more below).

Thus, I wanted to buy a non-OTG cable, as I thought I'd need it to connect other things to the iRulu, like the USB keyboard (that came with the iRulu package that I bought--in retrospect, that seems like a dumb thought--I should expect that iRulu would supply a cable that allows connection of the keyboard that is supplied with the iRulu (in the particular package I bought).

Currently I'm pretty sure that the non-OTG cable is not required (at least for anything I've tried so far), and I found it rather difficult to find a cable with the proper connectors which was not labeled as an OTG cable.

Both the OTG cable that came with the iRulu and the non-OTG cable I bought separately have a micro USB male connector on one end (as the jacks in the iRulu are micro USB female) and a standard size USB female connector on the other end.

I did some reading about OTG cables, and, iiuc, I know now I that on one end of an OTG cable, pin 4 is "shorted" to pin 5. (I'm assuming that pin 5 on the other end of the cable is not connected to anything, but I don't know that.)

Presumably (without doing any research), I'm assuming a non-OTG cable has pin 1 on one end of the cable connected to pin 1 on the other end, and similarly for all the other pins.

In a non-OTG cable, I'm assuming pin 5 is not connected on either end of the cable. (But maybe it is connected to any shield that may be present?)

I'm not 100% sure the cables I bought are really non-OTG--I am buying some micro USB female PC board connectors which I can then use to plug (one end) of the cables into and then start doing some tests with a VOM. (The pins and the space to access the pins on the micro USB connector are so close together I don't think I can reliably confirm which pin I have my test lead on.)

UPDATE: I received the micro USB female PC board connector--the size and spacing of the leads is so small that they won't help me much--but, at some point I'll see what I can do with a VOM. I might have to jury rig some very tiny probes, maybe out of something like sewing needles (or pins).

See Host vs. USB Ports for a discussion of my experience configuring the external USB keyboard, which has some data points about possible differences in functionality between the USB and Host ports and OTG and non-OTG cables.

I should point out that since the keyboard has been configured, whether I plug it into the USB or Host port, and use an OTG or a non-OTG cable, the keyboard is detected promptly and works fine in all 4 configurations.

UPDATE: I found what seemed to be a good article on OTG, then had an Iceweasel crash, and, somehow, that link wasn't saved. Anyway, what little I saw of the article before the crash indicated that the OTG cable might be needed to connect things like USB storage devices. So, that is something I will try at some point. I'm sure I'll try all four possibilities as discussed above, that is the four combinations of the USB and Host ports and OTG and non-OTG cables.

UPDATE: I think this may be the article I lost (although I thought it was longer): USB OTG: What it means and how to use it. It seems to say that OTG is needed to connect things like mice and keyboards--I'm not sure that is true. The last time I reset the iRulu and configured it, I did use the OTG cable and the Host port, so I don't know if configuration would have worked as well using the non-OTG cable into the USB port. However, since the keyboard has been configured, I can plug it into the USB or Host port, using the OTG or non-OTG cable and it works fine in all cases. (In my "normal" configuration, I plug the keyboard into the USB hub that is built-in to the USB 10/100 Ethernet adapter, and then plug that into the iRulu using the OTG cable into the Host port (although I'm not sure I'm always careful to choose the Host port vs. the USB port.))





  • () RandyKramer - 2014-02-27
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Topic revision: r7 - 2015-01-08 - RandyKramer
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