100 Msps Receive Support for USRP N210
======================================
To receive at 100 Msps, you'll need to load a modified FPGA image onto the N210 and use
UHD 003.004.000-ish library that works with FPGA compatibility version 9.0. The changes
are based on uhd/fpga/usrp2 pulled on 6-Apr-2012. No changes to uhd/host are required.
There are pre-built images and ISE projects for N210 revisions 3 and 4. The rev 3
image will also work on rev 2 boards.
The FPGA has no transmit logic, so it can only receive. We've tested it with a DBSRX2,
but other daughterboards should work.
In the modified FPGA, DSP 0 is unchanged and can be used for normal decimation to 25 Msps
or below. DSP 1 only supports 100 Msps.
To receive at 100 Msps, setup two channels:
usrp->set_rx_subdev_spec(uhd::usrp::subdev_spec_t("A:0 A:0"));
And specify channel 1 for set_rx_freq, get_rx_gain, etc.
When creating the rx_streamer, specify channel 1:
stream_args.channels.push_back(1);
uhd::rx_streamer::sptr rx_stream = usrp->get_rx_stream(stream_args);
When receiving at 100 Msps, a maximum of 2^18 (262,144) contiguous samples (the size of the
N210's SRAM) can be requested at a time. Only STREAM_MODE_NUM_SAMPS_AND_DONE is supported.
To receive at normal decimated rates, just use channel 0 or don't specify a channel.
The uhd_streamer.cpp command line app has details. We've built and used it on Ubuntu 10.04
and Windows 7 Pro. It also has a client/server facility to make a set of USRPs sharable
with several apps.
Load the FPGA
-------------
cd path/to/N210CeVI
# Substitute the IP address of your N210
/usr/local/share/uhd/utils/usrp_n2xx_net_burner.py --addr=192.168.10.2 --fpga=n210_r3.bin
or
/usr/local/share/uhd/utils/usrp_n2xx_net_burner.py --addr=192.168.10.2 --fpga=n210_r4.bin
# If that went okay, power cycle the N210 or:
/usr/local/share/uhd/utils/usrp_n2xx_net_burner.py --addr=192.168.10.2 --reset
Use similar commands on Windows.
Build uhd_streamer on Linux
---------------------------
cd path/to/N210CeVI
gcc uhd_streamer.cpp -o uhd_streamer -luhd
./uhd_streamer --help
Build uhd_streamer on Windows
-----------------------------
(I really need to create the cmake goo for this.)
I manually created a Visual Studio 10 project for a console app. I deleted the generated
.cpp file and added uhd_streamer.cpp. Then I added include directories for UHD and boost,
library directories for UHD and boost, and the UHD lib as a link input.