SDR (Software Defined Radio) Transceiver

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N4TLF
Posts: 7
Joined: Fri May 29, 2015 1:39 am

Re: SDR (Software Defined Radio) Transceiver

Post by N4TLF » Mon Jun 15, 2015 1:54 am

Just one more post....
I was just listening on 40 Meters to a couple hams in Florida talking to a ham in Western Australia (via long path over Africa), on my Red Pitaya. I checked the signal on my Elecraft K3, and it was about the same signal level! All this on a 40M dipole in the attic, in Charleston, SC, USA.

I think that has proven how sensitive the RP can be.
Terry, N4TLF

pavel
Posts: 618
Joined: Sat May 23, 2015 5:22 pm

Re: SDR (Software Defined Radio) Transceiver

Post by pavel » Wed Jun 17, 2015 8:25 am

W6MRR wrote: - Why go CORDIC when you have the hardware multipliers?
- How much of the PL did you use?
- Is there room for a second receive chain?
Hi Martin,

To compare CORDIC and DDS+Multiplier based SDR configurations, I added two new projects to my repository: sdr_receiver_dds and sdr_transceiver_dds.

Compared to the CORDIC based SDR configuration, the DDS+Multiplier based SDR configuration has the following particularities (sdr_transceiver_dds vs sdr_transceiver):
  • uses much less FF (42% vs 57%) and LUT (41% vs 77%) resources
  • uses slightly more BRAM (57% vs 51%) and DSP48 (64% vs 56%) resources
  • Xilinx Complex Multiplier IP core has the random rounding functionality
  • with random rounding, the TX signal is cleaner
Looking at the resource usage and taking into account that most of the BRAM and DSP48 resources are used by the spectrum display chain, I'd say that it's now possible to add a second receive chain and a second transmit chain to the DDS+Multiplier based SDR transceiver.

The source code of the DDS+Multiplier based SDR transceiver can be found at the following location:

https://github.com/pavel-demin/red-pita ... ceiver_dds

Best regards,

Pavel

dreschpe
Posts: 5
Joined: Fri May 15, 2015 8:32 pm

Re: SDR (Software Defined Radio) Transceiver

Post by dreschpe » Sat Jun 20, 2015 6:21 pm

Hello Pavel,
I have set up the development system and have compiled the sdr_receiver.bin
It generate a bitstream, but it is not working. I'm using the new system with the clock patch.
Shall it work with the actual git code ?

Regards,
Peter

dreschpe
Posts: 5
Joined: Fri May 15, 2015 8:32 pm

Re: SDR (Software Defined Radio) Transceiver

Post by dreschpe » Sat Jun 20, 2015 6:38 pm

Hello Pavel,
if I try to compile the receiver_dds I run into the error :
ERROR: [BD 5-216] VLNV <pavel-demin:user:axis_lfsr:1.0> is not supported for this version of the tools.

I think this is because I`m using the WebPACK.

Regards,
Peter

pavel
Posts: 618
Joined: Sat May 23, 2015 5:22 pm

Re: SDR (Software Defined Radio) Transceiver

Post by pavel » Sat Jun 20, 2015 8:35 pm

dreschpe wrote: I have set up the development system and have compiled the sdr_receiver.bin
It generate a bitstream, but it is not working. I'm using the new system with the clock patch.
Shall it work with the actual git code?
Hi Peter,

Could you please explain in more details how it is not working?

The FPGA code was only a part of the problem that I recently fixed. Increasing of the the FPGA clock frequency (~143 MHz) is done outside of the FPGA code. In the latest SD card image zip file, I'm using the following commands to increase the FPGA clock frequency:

Code: Select all

echo fclk0 >  /sys/devices/soc0/amba/f8007000.devcfg/fclk_export
echo 1 > /sys/devices/soc0/amba/f8007000.devcfg/fclk/fclk0/enable
echo 143000000 > /sys/devices/soc0/amba/f8007000.devcfg/fclk/fclk0/set_rate
These commands work with the latest Linux kernel provided by Xilinx and don't work with the original RedPitaya. To make the customized SD card image file, I replaced boot.bin, devicetree.dtb, uImage and uEnv.txt.

I know that I should update the "Building from source" instructions but I'm still not sure what method to use to increase the FPGA clock frequency.

Best regards,

Pavel

pavel
Posts: 618
Joined: Sat May 23, 2015 5:22 pm

Re: SDR (Software Defined Radio) Transceiver

Post by pavel » Sat Jun 20, 2015 8:45 pm

dreschpe wrote: if I try to compile the receiver_dds I run into the error :
ERROR: [BD 5-216] VLNV <pavel-demin:user:axis_lfsr:1.0> is not supported for this version of the tools.
I've just checked that it works with a freshly cloned git repository.

However, if you update your git repository and new cores are pulled to the cores directory then my Makefile is not checking for these new cores and the only solution is to manually remove tmp/cores:

Code: Select all

rm -rf tmp/cores
make NAME=sdr_receiver_dds tmp/sdr_receiver_dds.bit
I'll try to improve the make rules for the cores.

dreschpe
Posts: 5
Joined: Fri May 15, 2015 8:32 pm

Re: SDR (Software Defined Radio) Transceiver

Post by dreschpe » Mon Jun 22, 2015 5:51 pm

Hi Pavel,
i have reload your git and the compiled sdr_receiver is working fine. I have checked it with my signal generator - perfect.

The sdr_ receiver_dds shows a spectrum, but the network led is flashing slowly. You hear wow-wow - I think the PC get only a fraction of the packets.
I have to investigate deeper.

I'm using the new SD Card image to boot and reload the FPGA via a SSH connection.

Peter,
DC2PD

pavel
Posts: 618
Joined: Sat May 23, 2015 5:22 pm

Re: SDR (Software Defined Radio) Transceiver

Post by pavel » Mon Jun 22, 2015 8:45 pm

dreschpe wrote: The sdr_ receiver_dds shows a spectrum, but the network led is flashing slowly. You hear wow-wow - I think the PC get only a fraction of the packets.
Hi Peter,

Is it possible that you are using sdr_ receiver_dds.bit with the sdr-receiver (without -dds) server?

sdr_ receiver_dds.bit should be used with the sdr-receiver-dds server.

It can be built with the following command:

Code: Select all

arm-xilinx-linux-gnueabi-gcc projects/sdr_receiver_dds/server/sdr-receiver-dds.c -o sdr-receiver-dds -lm -static
Best regards,

Pavel

MartinR
Posts: 6
Joined: Wed May 27, 2015 3:15 am

Re: SDR (Software Defined Radio) Transceiver

Post by MartinR » Tue Jun 23, 2015 6:52 pm

Hello Pavel,

Real great work and interesting results. I've yet to set up your development environment but am anxious to try out the code. Could you include .bin files for the transceivers please?

Thanks,

Martiin W6MRR

Eduscho
Posts: 1
Joined: Tue Jul 14, 2015 5:46 pm

Re: SDR (Software Defined Radio) Transceiver

Post by Eduscho » Tue Jul 14, 2015 10:22 pm

Hi,

I'm following this thread with great interest. However, I've difficulties to conclude how the RP performs compared to other SDR boards/solutions. Can we expect higher performance (noise, dynamic, immunity) than with RTL-SDR? How about hack-rf/bladerf comparison? Or AirSpy?

Is RP a good base for extensions like down-convertes, maybe an I/Q Stage in front?

Regards,
Ed

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