Overview
1. What is OTG?
- An OTG product is a portable device that uses a single Micro-AB receptacle (and no other USB receptacles) to operate at times as a USB Targeted Host and at times as a USB peripheral. OTG devices must always operate as a standard peripheral when connected to a standard USB host.
2. What are targeted Hosts?
- A target host is a USB host that supports specific, targeted set of peripherals.
- TPL (Targeted Peripheral List) is the set of selected peripherals defined by developer of each targeted host.
3. How Targeted Host is different from PC Host?
By definition, USB communication occurs between a host and a peripheral. The original intent was to
place the heavier workload on the PC (host) and to allow USB peripherals to be fairly simple.Accordingly, the USB specification requires that PCs:
- provide power to peripherals (for [USB2.0] 0.5A at ~5V, for [USB3.0] 0.9A at ~5V)
- support all defined speeds (SuperSpeed, Low Speed, Full Speed and High Speed)
- support all defined data flow types (control, bulk, interrupt and isochronous)
A Targeted Host is a USB host that supports a specific, targeted set of peripherals. The developer of each Targeted Host product defines the set of supported peripherals on a Targeted Peripheral List (TPL). A Targeted Host needs to provide only the power, bus speeds, data flow types, etc., that the peripherals on its TPL require.
4. What are the differences between SS Embedded Host and SS On The Go?
An Embedded Host (EH) product provides Targeted Host functionality over one or more Standard-A receptacles.
- Embedded Host products may also offer USB peripheral capability, delivered separately via one or more Type-B receptacles.
- An OTG product is a portable device that uses a single Micro-AB receptacle (and no other USB receptacles) to operate at times as a USB Targeted Host and at times as a USB peripheral.
- OTG devices must always operate as a standard peripheral when connected to a standard USB host.
5. What is SuperSpeed Peripheral only device?
SuperSpeed Peripheral Only or SS-PO: A peripheral-only B-device which can operate at
SuperSpeed in addition to having peripheral-only B-device capabilities as described in [OTG&EH2.0].
6. What is SuperSpeed Peripheral capable OTG device?
An OTG device compliant with [OTG&EH2.0] which can also operate as a SuperSpeed peripheral. Products with this configuration are not able to operate as a SuperSpeed host. When operating as a peripheral, they can operate at either SuperSpeed or [OTG&EH2.0] speeds. However they are only able to swap roles when operating at [OTG&EH2.0] speeds.
7. Does SuperSpeed OTG Device support Full Speed and High Speed Transactions?
Of course. An OTG Device compliant with [OTG&EH2.0] which can also operate as a SuperSpeed Host or a SuperSpeed Peripheral.
Devices which conform to [OTG&EH2.0] are referred to as [USB2.0] devices in this supplement: USB2.0
EH, USB2.0 OTG and USB2.0 PO.
8. What is RSP?
RSP stands for “Role Swap Protocol”. This protocol is used to swap the roles between two OTG devices (OTG A device and OTG B device) as HOST and PERIPHERAL.As by default, Id pin (a special pin on OTG cable) decides which OTG device works as a HOST and PERIPHERAL.
When Id pin is grounded (Id = 0) then this OTG device will work as HOST and called A-Device and other device that has the Id value equal to one (Id = 1) will work as PERIPHERAL and called B-device.
9. What are A and B devices?
A-Device: Device with a Standard-A receptacle or a device with a Micro-A plug inserted into its receptacle. The A-device supplies power to VBUS (drives the VBUS) and is host at the start of a session. If the A-device is On-The-Go (equipped with a Micro-AB receptacle), it may relinquish the role of host to an On-The-Go B-device under certain conditions.
B-Device: Device with:
a Standard-B receptacle or
Mini-B receptacle, or
Micro-B receptacle, or
Micro-AB receptacle with either a Micro-B plug or no plug inserted into its receptacle, or a captive cable ending in a Standard-A or Micro-A plug.
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