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103 lines
3.6 KiB
ReStructuredText
103 lines
3.6 KiB
ReStructuredText
========================================================================
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UHD - USRP1 Application Notes
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========================================================================
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.. contents:: Table of Contents
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------------------------------------------------------------------------
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Comparative features list
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------------------------------------------------------------------------
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* 2 transceiver card slots
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* 2 RX DDC chains in FPGA
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* 2 TX DUC chains in FPGA (no TX CORDIC -> uses DAC)
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* 64 MHz fixed clock rate
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* sc16 sample modes
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* sc8 sample mode - RX only
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------------------------------------------------------------------------
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Specify a Non-standard Image
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------------------------------------------------------------------------
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The standard USRP1 images installer comes with two FPGA images:
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* **usrp1_fpga.rbf:** 2 DDCs + 2 DUCs
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* **usrp1_fpga_4rx.rbf:** 4 DDCs + 0 DUCs
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By default, the USRP1 uses the FPGA image with 2 DDCs and 2 DUCs.
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However, a device address parameter can be used to override
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the FPGA image selection to use an alternate or a custom FPGA image.
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See the images application notes for installing custom images.
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Example device address string representations to specify non-standard firmware and/or FPGA images:
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::
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fpga=usrp1_fpga_4rx.rbf
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-- OR --
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fw=usrp1_fw_custom.ihx
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-- OR --
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fpga=usrp1_fpga_4rx.rbf, fw=usrp1_fw_custom.ihx
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------------------------------------------------------------------------
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Missing and Emulated Features
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------------------------------------------------------------------------
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The USRP1 FPGA does not have the necessary space to support the advanced
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streaming capabilities that are possible with the newer USRP devices.
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Some of these features are emulated in software to support the API.
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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List of emulated features
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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* Setting the current device time
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* Getting the current device time
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* Transmitting at a specific time
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* Transmitting a specific number of samples
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* Receiving at a specific time
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* Receiving a specific number of samples
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* End of burst flags for transmit/receive
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* Notification on late stream command
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* Notification on late transmit packet
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* Notification on underflow or overflow
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* Notification on broken chain error
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**Note:**
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These emulated features rely on the host system's clock for timed operations
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and therefore may not have sufficient precision for the application.
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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List of missing features
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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* Start of burst flags for transmit/receive
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------------------------------------------------------------------------
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Hardware Setup Notes
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------------------------------------------------------------------------
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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External clock modification
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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The USRP device can be modified to accept an external clock reference instead of the 64MHz onboard reference.
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* Solder SMA (**LTI-SASF54GT**) connector to **J2001**.
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* Move 0 ohm 0603 resistor **R2029** to **R2030**.
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* Move 0.01uF 0603 capacitor **C925** to **C926**.
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* Remove 0.01uF 0603 capacitor **C924**.
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The new external clock needs to be a square wave between +7dBm and +15dBm
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After the hardware modification,
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the user should burn the setting into the EEPROM,
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so UHD software can initialize with the correct clock rate.
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Run the following commands to record the setting into the EEPROM:
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::
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cd <install-path>/share/uhd/utils
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./usrp_burn_mb_eeprom --args=<optional device args> --key=mcr --val=<rate>
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The user may override the clock rate specified in the EEPROM by using a device address:
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Example:
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::
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uhd_usrp_probe --args="mcr=52e6"
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