Adding DSP logic to Generation 2 products

As part of the USRP FPGA build-framework, there are several convenient places for users to insert custom DSP modules into the transmit and receive chains.

Before the DDC module
After the DDC module
Replace the DDC module
Before the DUC module
After the DUC module
Replace the DUC module
As an RX packet engine
As an TX packet engine

Customizing the top level makefile

Each USRP device has a makefile associated with it. This makefile contains all of the necessary build rules. When making a customized FPGA design, start by copying the current makefile for your device. Makefiles can be found in usrp2/top/{product}/Makefile

Edit your new makefile:

Set BUILD_DIR to a unique directory name
Set CUSTOM_SRCS for your verilog sources
Set CUSTOM_DEFS (see section below)

Inserting custom modules

CUSTOM_DEFS is a string of space-separate key-value pairs. Set the CUSTOM_DEFS variable so the FPGA fabric glue will substitute your custom modules into the DSP chain.

Example:

CUSTOM_DEFS = "TX_ENG0_MODULE=my_tx_engine RX_ENG0_MODULE=my_rx_engine"

Where my_tx_engine and my_rx_engine are the names of custom verilog modules.

The following module definition keys are possible (X is a DSP number):

TX_ENG<X>_MODULE: Set the module for the transmit chain engine.
RX_ENG<X>_MODULE: Set the module for the receive chain engine.
RX_DSP<X>_MODULE: Set the module for the transmit dsp chain.
TX_DSP<X>_MODULE: Set the module for the receive dsp chain.

Examples of custom modules can be found in usrp2/custom/*.v