USRP Source: Difference between revisions

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Block used to stream samples from a USRP device.   
[[Category:Block Docs]]
Block used to stream samples from a USRP device (i.e. act as the receiver).   


To adjust parameters like Center Frequency while running, use [[QT GUI Range]] or another control.   
To adjust parameters like Center Frequency while running, use [[QT GUI Range]] or another control.   
There is no need to use a [[Throttle]] block when a hardware source like a USRP Source is used, because the USRP acts as the throttle.


The input message port called "command" can be used to change frequency, gain, and other parameters via [[Message Passing]].  A common arrangement is to use the [[QT GUI Frequency Sink]]'s output message port and connect it to the USRP Source's input port, so that when a user double-clicks within the GUI to change frequency, the change gets propagated to the USRP device.  See example flowgraph below for how this is connected.
The input message port called "command" can be used to change frequency, gain, and other parameters via [[Message Passing]].  A common arrangement is to use the [[QT GUI Frequency Sink]]'s output message port and connect it to the USRP Source's input port, so that when a user double-clicks within the GUI to change frequency, the change gets propagated to the USRP device.  See example flowgraph below for how this is connected.


[[File:usrp_source_ex_flowgraph.png|300px]]
== Parameters ==


[[File:usrp_source_ex_flowgraph_output.png|500px]]
; Output Type
: This parameter controls the data type of the output stream in GNU Radio.


'''Parameters:'''
; Wire Format
: This parameter controls the form of the data over the bus/network. Complex bytes may be used to trade off precision for bandwidth. Not all formats are supported on all devices.


Output Type - This parameter controls the data type of the output stream in GNU Radio.
; Stream Args
: Optional arguments to be passed in the UHD streamer object. Streamer args is a list of key/value pairs; usage is determined by the implementation.  [https://files.ettus.com/manual/structuhd_1_1stream__args__t.html#a4463f2eec2cc7ee70f84baacbb26e1ef Docs for stream args]


Wire Format - This parameter controls the form of the data over the bus/network. Complex bytes may be used to trade off precision for bandwidth. Not all formats are supported on all devices.
; Stream Channels
: Optionally used to specify which channels are used, e.g. [0,1]


Stream Args - Optional arguments to be passed in the UHD streamer object. Streamer args is a list of key/value pairs; usage is determined by the implementation.  [https://files.ettus.com/manual/structuhd_1_1stream__args__t.html#a4463f2eec2cc7ee70f84baacbb26e1ef Docs for stream args]
; Devices Address
 
: The device address is a delimited string used to locate UHD devices on your system. If left blank, the first UHD device found will be used. Use the device address to specify a specific device or list of devices.
Stream Channels - Optionally used to specify which channels are used, e.g. [0,1]
 
Devices Address - The device address is a delimited string used to locate UHD devices on your system. If left blank, the first UHD device found will be used. Use the device address to specify a specific device or list of devices.


     Examples: serial=12345678
     Examples: serial=12345678
Line 25: Line 29:
               addr0=192.168.10.2, addr1=192.168.10.3
               addr0=192.168.10.2, addr1=192.168.10.3


Device Arguments -
; Device Arguments
: Other various arguments that can be passed to the USRP Source, see [http://files.ettus.com/manual/page_configuration.html USRP Device Configuration]
 
; Sync
: Can be used to get USRP to attempt to sync to either PC's clock, or PPS signal if it exists.
 
; Clock Rate [Hz]
: The clock rate shouldn't be confused with sample rate, but they are related.  The B2X0 and E31X USRPs use a flexible clock rate that will either be equal to the requested sample rate, or a multiple of it.  Best left to default unless specific behavior is needed.


Sync - Can be used to get USRP to attempt to sync to either PC's clock, or PPS signal if it exists.
; Num Mboards
: Selects the number of USRP motherboards (i.e. physical USRP devices) in this device configuration.


Clock Rate [Hz] - The clock rate shouldn't be confused with sample rate, but they are related. The B2X0 and E31X USRPs use a flexible clock rate that will either be equal to the requested sample rate, or a multiple of itBest left to default unless specific behavior is needed.
; Mbx Clock Source
: Where the motherboard should sync its clock references. External refers to the 10 MHz input on the USRPO/B GPSDO is the optional onboard GPSDO module, which provides its own 10 MHz (and PPS) signals.


Num Mboards - Selects the number of USRP motherboards (i.e. physical USRP devices) in this device configuration.
; Mbx Time Source
: Where the motherboard should sync its time references. External refers to the PPS input on the USRP.  O/B GPSDO is the optional onboard GPSDO module, which provides its own PPS (and 10 MHz) signals.


Mbx Clock Source - Where the motherboard should sync its time and clock references. External refers to the 10 MHz and PPS input on the USRP. O/B GPSDO is the optional onboard GPSDO module, which provides its own 10 MHz and PPS signals.
; Mbx Subdev Spec
: Each motherboard should have its own subdevice specification and all subdevice specifications should be the same length. Select the subdevice or subdevices for each channel using a markup string. The markup string consists of a list of dboard_slot:subdev_name pairs (one pair per channel). If left blank, the UHD will try to select the first subdevice on your system. See the application notes for further details.Single channel example: ":AB"


Mbx Subdev Spec - Each motherboard should have its own subdevice specification and all subdevice specifications should be the same length. Select the subdevice or subdevices for each channel using a markup string. The markup string consists of a list of dboard_slot:subdev_name pairs (one pair per channel). If left blank, the UHD will try to select the first subdevice on your system. See the application notes for further details.Single channel example: ":AB"
; Num Channels
: Selects the total number of channels in this multi-USRP configuration. Ex: 4 motherboards with 2 channels per board = 8 channels total.


Num Channels - Selects the total number of channels in this multi-USRP configuration. Ex: 4 motherboards with 2 channels per board = 8 channels total.
; Sample Rate
: The number of samples per second, which is equal to the bandwidth in Hz we wish to observe. The UHD device driver will try its best to match the requested sample rate. If the requested rate is not possible, the UHD block will print an error at runtime.


Sample Rate - The number of samples per second, which is equal to the bandwidth in Hz we wish to observe. The UHD device driver will try its best to match the requested sample rate. If the requested rate is not possible, the UHD block will print an error at runtime.
; Chx Center Frequency
: The center frequency is the overall frequency of the RF chain.


Chx Center Frequency - The center frequency is the overall frequency of the RF chain.
; Chx Gain Value
: Value used for gain, which is either between 0 and the max gain for the USRP (usually around 70 to 90), when using the default "Absolute" Gain Type.  When using "Normalized" Gain Type, it will always be 0.0 to 1.0, where 1.0 will be mapped to the max gain of the USRP being used.


Chx Gain Value - Value used for gain, which is either between 0 and the max gain for the USRP (usually around 70 to 90), when using the default "Absolute" Gain Type.  When using "Normalized" Gain Type, it will always be 0.0 to 1.0, where 1.0 will be mapped to the max gain of the USRP being used.
; Chx Gain Type
: Absolute (in dB) or Normalized (0 to 1)


Chx Gain Type - Absolute (in dB) or Normalized (0 to 1)
; Chx Antenna
: For subdevices with only one antenna, this may be left blank. Otherwise, the user should specify one of the possible antenna choices. See the daughter-board application notes for the possible antenna choices.


Chx Antenna - For subdevices with only one antenna, this may be left blank. Otherwise, the user should specify one of the possible antenna choices. See the daughter-board application notes for the possible antenna choices.
; Chx Bandwidth
: The bandwidth used by the USRP's anti-aliasing filter.  To use the default bandwidth filter setting, this should be zero. Only certain subdevices have configurable bandwidth filters. See the daughterboard application notes for possible configurations.


Chx Bandwidth - The bandwidth used by the USRP's anti-aliasing filter. To use the default bandwidth filter setting, this should be zero. Only certain subdevices have configurable bandwidth filters. See the daughterboard application notes for possible configurations.
; Chx Enable DC Offset Correction
: Attempts to remove the DC offset, i.e. the average value of a signal, which is something that will be very visible in the Frequency domain.  


Chx Enable DC Offset Correction -
; Chx Enable IQ Imbalance Correction
: Attempts to correct any IQ imbalance, which is when there is a mismatch between the I and Q signal paths, typically causing a stretching effect to a constellation.


Chx Enable IQ Imbalance Correction -
== Example Flowgraph ==
 
The example flowgraph below shows basic usage of a USRP Source.  It also shows how the message ports can be connected so that changing the frequency from within the [[QT GUI Frequency Sink]], by double clicking within the GUI, is propagated to the USRP.  Variables are used to set the sample rate and center frequency.
 
[[File:usrp_source_ex_flowgraph.png|350px]]
 
[[File:usrp_source_ex_flowgraph_output.png|500px]]

Revision as of 02:00, 27 June 2019

Block used to stream samples from a USRP device (i.e. act as the receiver).

To adjust parameters like Center Frequency while running, use QT GUI Range or another control.

There is no need to use a Throttle block when a hardware source like a USRP Source is used, because the USRP acts as the throttle.

The input message port called "command" can be used to change frequency, gain, and other parameters via Message Passing. A common arrangement is to use the QT GUI Frequency Sink's output message port and connect it to the USRP Source's input port, so that when a user double-clicks within the GUI to change frequency, the change gets propagated to the USRP device. See example flowgraph below for how this is connected.

Parameters

Output Type
This parameter controls the data type of the output stream in GNU Radio.
Wire Format
This parameter controls the form of the data over the bus/network. Complex bytes may be used to trade off precision for bandwidth. Not all formats are supported on all devices.
Stream Args
Optional arguments to be passed in the UHD streamer object. Streamer args is a list of key/value pairs; usage is determined by the implementation. Docs for stream args
Stream Channels
Optionally used to specify which channels are used, e.g. [0,1]
Devices Address
The device address is a delimited string used to locate UHD devices on your system. If left blank, the first UHD device found will be used. Use the device address to specify a specific device or list of devices.
   Examples: serial=12345678
             addr=192.168.10.2
             addr0=192.168.10.2, addr1=192.168.10.3
Device Arguments
Other various arguments that can be passed to the USRP Source, see USRP Device Configuration
Sync
Can be used to get USRP to attempt to sync to either PC's clock, or PPS signal if it exists.
Clock Rate [Hz]
The clock rate shouldn't be confused with sample rate, but they are related. The B2X0 and E31X USRPs use a flexible clock rate that will either be equal to the requested sample rate, or a multiple of it. Best left to default unless specific behavior is needed.
Num Mboards
Selects the number of USRP motherboards (i.e. physical USRP devices) in this device configuration.
Mbx Clock Source
Where the motherboard should sync its clock references. External refers to the 10 MHz input on the USRP. O/B GPSDO is the optional onboard GPSDO module, which provides its own 10 MHz (and PPS) signals.
Mbx Time Source
Where the motherboard should sync its time references. External refers to the PPS input on the USRP. O/B GPSDO is the optional onboard GPSDO module, which provides its own PPS (and 10 MHz) signals.
Mbx Subdev Spec
Each motherboard should have its own subdevice specification and all subdevice specifications should be the same length. Select the subdevice or subdevices for each channel using a markup string. The markup string consists of a list of dboard_slot:subdev_name pairs (one pair per channel). If left blank, the UHD will try to select the first subdevice on your system. See the application notes for further details.Single channel example: ":AB"
Num Channels
Selects the total number of channels in this multi-USRP configuration. Ex: 4 motherboards with 2 channels per board = 8 channels total.
Sample Rate
The number of samples per second, which is equal to the bandwidth in Hz we wish to observe. The UHD device driver will try its best to match the requested sample rate. If the requested rate is not possible, the UHD block will print an error at runtime.
Chx Center Frequency
The center frequency is the overall frequency of the RF chain.
Chx Gain Value
Value used for gain, which is either between 0 and the max gain for the USRP (usually around 70 to 90), when using the default "Absolute" Gain Type. When using "Normalized" Gain Type, it will always be 0.0 to 1.0, where 1.0 will be mapped to the max gain of the USRP being used.
Chx Gain Type
Absolute (in dB) or Normalized (0 to 1)
Chx Antenna
For subdevices with only one antenna, this may be left blank. Otherwise, the user should specify one of the possible antenna choices. See the daughter-board application notes for the possible antenna choices.
Chx Bandwidth
The bandwidth used by the USRP's anti-aliasing filter. To use the default bandwidth filter setting, this should be zero. Only certain subdevices have configurable bandwidth filters. See the daughterboard application notes for possible configurations.
Chx Enable DC Offset Correction
Attempts to remove the DC offset, i.e. the average value of a signal, which is something that will be very visible in the Frequency domain.
Chx Enable IQ Imbalance Correction
Attempts to correct any IQ imbalance, which is when there is a mismatch between the I and Q signal paths, typically causing a stretching effect to a constellation.

Example Flowgraph

The example flowgraph below shows basic usage of a USRP Source. It also shows how the message ports can be connected so that changing the frequency from within the QT GUI Frequency Sink, by double clicking within the GUI, is propagated to the USRP. Variables are used to set the sample rate and center frequency.

Usrp source ex flowgraph.png

Usrp source ex flowgraph output.png