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Diffstat (limited to 'host/docs')
| -rw-r--r-- | host/docs/vrt_chdr.dox | 30 |
1 files changed, 14 insertions, 16 deletions
diff --git a/host/docs/vrt_chdr.dox b/host/docs/vrt_chdr.dox index ae670a67d..6eb1fc17f 100644 --- a/host/docs/vrt_chdr.dox +++ b/host/docs/vrt_chdr.dox @@ -6,22 +6,21 @@ Radio transport protocols are used to exchange samples (or other items) between If one were to sniff Ethernet traffic between a USRP and a PC, the packets would conform to a radio transport protocol. -For USRP devices, three radio transport protocols are relevant: CHDR, Legacy -CHDR (from UHD 3.x) and VRT (the VITA Radio Transport protocol). - -All Generation-3 devices use CHDR. Prior to UHD 4.0, Generation-3 devices used -legacy CHDR. The B200 continues to use the legacy CHDR format. All other -Generation-1 and Generation-2 devices use VRT. - +For USRP devices, three radio transport protocols are relevant: +- CHDR (used by all Generation-3 and above devices) +- Legacy CHDR. All RFNoC devices used to use this in UHD 3.x. In current versions, + only B200 series uses it. +- VRT (the VITA Radio Transport protocol). This is used by Generation-1 and + Generation-2 devices. \section rtp_chdr CHDR -The CHDR protocol is described in detail in the +The CHDR protocol is described in detail in the [RFNoC Specification](https://files.ettus.com/app_notes/RFNoC_Specification.pdf). Please refer to the specification document for protocol format information. -\section rtp_legacy_chdr Legacy CHDR +\section rtp_legacy_chdr Legacy CHDR (Used by B200-series devices) For the third generation of Ettus devices, a new type transport protocol was designed. It reduces the complexity of the original standard and uses a fixed-length 64-Bit header @@ -32,8 +31,6 @@ By compressing all information into a 64-bit line, the header can efficiently be in newer FPGAs, where the common streaming protocol is 64-Bit AXI. The first line in a packet already provides all necessary information to proceed. -Some CHDR-specific functions can be found in: uhd::transport::vrt::chdr. - The form of a CHDR packet is the following: Address (Bytes) | Length (Bytes) | Payload @@ -53,7 +50,7 @@ Bits | Meaning 60 | End-of-burst or error flag 59:48 | 12-bit sequence number 47:32 | Total packet length in Bytes -31:0 | Stream ID (SID). For the format of SID, see uhd::sid_t. +31:0 | Stream ID (SID). The packet type is determined mainly by the first two bits, although the EOB or error flag are also taken into consideration (the third bit does not @@ -71,12 +68,15 @@ Bit 63 | Bit 62 | Bit 61 | Bit 60 | Packet Type \section rtp_vrt VRT -VRT is an open protocol defined by the VITA-49 standard. It was designed for interoperability, -and to allow different device types to work with different software stacks. +VRT is an open protocol defined by the VITA-49 standard. It was designed for +interoperability, and to allow different device types to work with different +software stacks. VRT is a very verbose standard, and only a subset is implemented in UHD/USRPs. The full standard is available from the VITA website: http://www.vita.com . +Note that USRP 1 and 2 do not use VRL. Only VRT (version 49.0) is used, with some +USRP-specific modifications. \section vrt_tools Tools @@ -87,8 +87,6 @@ for Ethernet links as well as USB (e.g., for the B210). Relevant code sections for the radio transport layer are: * uhd::transport::vrt - Namespace for radio transport protocol related functions and definitions -* uhd::transport::vrt::chdr - Sub-namespace specifically for CHDR -* uhd::sid_t - Datatype to represent SIDs */ // vim:ft=doxygen: |