Hot!USB and OTG informations

Author
Emcy
Super Member
  • Total Posts : 562
  • Reward points : 0
  • Joined: 2008/01/09 03:37:06
  • Location: 0
  • Status: offline
2018/04/13 05:11:33 (permalink)
0

USB and OTG informations

Hello,
 
When you connect 2 OTG systems with a micro-USB cable, host must be micro-USB type A and device must be micro-USB type B, isn't it ?
I don't understand why phone connectors are micro-USB type B and not micro-USB type AB : someone know why ?
 
Thanks
post edited by Emcy - 2018/04/16 00:35:33
#1

10 Replies Related Threads

    maxruben
    Super Member
    • Total Posts : 3292
    • Reward points : 0
    • Joined: 2011/02/22 03:35:11
    • Location: Sweden
    • Status: offline
    Re: USB and OTG informations 2018/04/13 09:22:13 (permalink)
    0
    Mostly the phone is used as a device connected to a PC?
     
    /Ruben
    #2
    Antipodean
    Super Member
    • Total Posts : 1667
    • Reward points : 0
    • Joined: 2008/12/09 10:19:08
    • Location: Didcot, United Kingdom
    • Status: offline
    Re: USB and OTG informations 2018/04/14 05:45:58 (permalink)
    0
    Emcy
    Hello,
     
    When you connect 2 OTG systems with a micro-USB cable, host must be micro-USB type A and device must be micro-USB type B, isn't it ?
    I don't understand why phone connectors are micro-USB type B and not micro-USB type A : someone know why ?
     
    Thanks




    The two devices are identical, the difference is in the two ends of the cable. That is why the connector has 5 pins instead of 4.
     

    Do not use my alias in your message body when replying, your message will disappear ...

    Alan
    #3
    RISC
    Super Member
    • Total Posts : 5355
    • Reward points : 0
    • Status: offline
    Re: USB and OTG informations 2018/04/14 14:43:31 (permalink)
    0
    Hi,
    If you connect 2 OTG devices, the cable needed is "special" (5th signal).
    The reason is that when it starts enumeration each must know if it starts as HOST or DEVICE.
    One end of the cable has a 5th signal called SENSE or ID.
    If it is connected to GND then this side is the HOST and the other side is device (SENSE or ID is not connected).
    Regards
     
    #4
    Emcy
    Super Member
    • Total Posts : 562
    • Reward points : 0
    • Joined: 2008/01/09 03:37:06
    • Location: 0
    • Status: offline
    Re: USB and OTG informations 2018/04/16 00:43:48 (permalink)
    0
    maxruben
    Mostly the phone is used as a device connected to a PC?

    A phone can be connected to a PC : it would be normal that phone connector is micro-USB type B because VBUS is powered by PC.
    ... But a phone can be connected to a phone : it is why, it would be more logic that phone connector is micro-USB type AB.
    Problem is when I check a phone, I see micro-USB connector is type B and not type AB. With micro-USB type B connector, you can't use micro-USB type A cable and with micro-USB type AB connector, you can use all micro-USB cable type : why phone manufacturers doesn't use micro-USB type AB connector to be compatible with all cable type ? I think there is a reason, isn't it ?
     
    I must develop a USB OTG product (not a phone) and I would to know if I must use micro-USB type AB or type B.
     
    post edited by Emcy - 2018/04/16 01:40:37
    #5
    qɥb
    Monolothic Member
    • Total Posts : 3332
    • Reward points : 0
    • Joined: 2017/09/09 05:07:30
    • Location: Jupiter
    • Status: offline
    Re: USB and OTG informations 2018/04/16 02:02:58 (permalink)
    0
    I've never seen a micro-AB receptacle.
    The idea seems to have quietly died, and all the cables just have micro-B plugs at both ends.

    This forum is mis-configured so it only works correctly if you access it via https protocol.
    The Microchip website links to it using http protocol. Will they ever catch on?
    PicForum "it just works"
    #6
    Alpha Whisky
    Super Member
    • Total Posts : 48
    • Reward points : 0
    • Joined: 2014/10/02 07:05:22
    • Location: 0
    • Status: offline
    Re: USB and OTG informations 2018/04/16 05:07:28 (permalink)
    0
    Indeed. I have seen a few micro-AB sockets (mostly on evaluation kits) but they seem to have died out.
     
    I suspect that mobile phone manufacturers made the pragmatic decision that it was better to not follow the standard than have complaints from ham-fisted punters breaking AB sockets trying to plug B charging cables in upside down, the trapezoidal shape of the micro-B socket making it easier to work out orientation than the rectangular micro-AB.
     
    The only time it has been an issue for me was with the Raspberry Pi zero which also used a micro-B socket where it should have been micro-AB, I had to buy a non compliant micro-B to full size USB A socket adapter even though I had a perfectly good compliant micro-A to full size USB A adapter lying around (from an evaluation kit).
     
    The obvious answer would be for the USB association to chase the miscreants and stop them using the USB logo for non compliant designs. As the mobile manufacturers are some of the biggest contributors to the USB association it isn't going to happen.
    #7
    Emcy
    Super Member
    • Total Posts : 562
    • Reward points : 0
    • Joined: 2008/01/09 03:37:06
    • Location: 0
    • Status: offline
    Re: USB and OTG informations 2018/04/16 06:22:35 (permalink)
    0
    Alpha Whisky
    The obvious answer would be for the USB association to chase the miscreants and stop them using the USB logo for non compliant designs. As the mobile manufacturers are some of the biggest contributors to the USB association it isn't going to happen.

    It isn't sure that it is forbiden by USB association : I don't find this information.
    #8
    Antipodean
    Super Member
    • Total Posts : 1667
    • Reward points : 0
    • Joined: 2008/12/09 10:19:08
    • Location: Didcot, United Kingdom
    • Status: offline
    Re: USB and OTG informations 2018/04/16 06:39:16 (permalink)
    0
    Alpha Whisky
    The obvious answer would be for the USB association to chase the miscreants and stop them using the USB logo for non compliant designs. As the mobile manufacturers are some of the biggest contributors to the USB association it isn't going to happen.



    What a load of nonsense.
     
    All the current model phones use OTG, it can be a device attached to a PC for downloading stuff, or you can plug a USB memory stick into it, so the phone is now acting as a master. I have a 32GB memory stick that has a standard USB A socket one end and a micro-USB connector the other end just for this purpose.
     
    The phone manufacturers are using the correct connector.

    Do not use my alias in your message body when replying, your message will disappear ...

    Alan
    #9
    Alpha Whisky
    Super Member
    • Total Posts : 48
    • Reward points : 0
    • Joined: 2014/10/02 07:05:22
    • Location: 0
    • Status: offline
    Re: USB and OTG informations 2018/04/16 07:04:25 (permalink)
    0
    Emcy
     
    It isn't sure that it is forbiden by USB association : I don't find this information.

    Section 3.1.1 of On-The-Go and Embedded Host Supplement and section 4.5 of MicroUSB Specification to the USB 2.0 Specification.
     
    #10
    Jump to:
    © 2018 APG vNext Commercial Version 4.5