Radar Video Signal Processor

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Farren
Posts: 10
Joined: Tue Sep 15, 2015 11:07 am

Radar Video Signal Processor

Post by Farren » Fri Sep 18, 2015 10:32 am

Sorry for the long explanation below:

I am experimenting with my Red Pitaya that I just received.
I would like to use the board to replace one of my older products that uses a SHARC DSP for radar signal processor ( I used the ADSP20162 DSP ).
The product is a Weather Radar Signal processor and control system. The analog signal to quire
is a Log VIDEO signal,non Doppler. The sample rate of the ADC must be 10MHz.
No complex down conversion is needed, I have my own signal processor algorithm to average samples.

What I want to achieve is the following:
Trigger ADC conversion with the external Trigger ( PIN 3, E1 ).
Write raw samples to on board memory ( 4096 samples for each trigger ).
The trigger will come up every 4 Milliseconds ( the radar PRF is 250Hz ) this is not fast.
After collecting 4 x 4096 samples I will do a processing algorithm to produce 1 beam of processed data which must be sent to a host PC via Ethernet for display and logging while the next group of 4 sample blocks are collected simultaneously.
I also want to ingest other data into the Red Pitaya via UART serial port and SPI port, this data will come from another slave board that monitors antenna position etc.

I have many years of embedded C programming experience.
I also design and manufacture DSP and MCU hardware.
The drawback is that I have very little basic Linux experience and basic FPGA experience.
I would like to achieve the above without having to modify the FPGA contents or write complicated drivers.
Before I put an effort into this I would like to know if what I want to do is possible.

Some questions:
Is the external Trigger a true trigger with low latency before samples start to be sent to memory ?
The latency must not have a lot of jitter. Or is the trigger a polled software trigger ?
Can my application be achieved by using the acquire command or must I write a dedicated C program ?
Can the acquire command be triggered with external trigger ?
Are there some examples of using the SPI port to read from a slave chip ?
Are there some examples on using the spare UART serial port on E2?
Can I toggle ( ON/OFF ) a GPIO port easily ? ( want to use this to monitor timing with a Logic analyser ).

Thanks
Farren

Nils Roos
Posts: 1441
Joined: Sat Jun 07, 2014 12:49 pm
Location: Königswinter

Re: Radar Video Signal Processor

Post by Nils Roos » Fri Sep 18, 2015 8:28 pm

Hi Farren,

it appears to me that all of your requirements can be met with your stated level of experience quite comfortably.
Is the external Trigger a true trigger with low latency before samples start to be sent to memory ?
When the scope is armed to wait for a trigger event, it starts recording into an internal circular buffer. The trigger signal stores the current write position into a register and starts a counter after whose expiry recording stops. This happens within the FPGA fabric, no processor intervention involved.
The latency must not have a lot of jitter. Or is the trigger a polled software trigger ?
The external trigger signal is fed into a three stage clock synchronisation register. This causes jitter on the order of +/- 8ns. That is the only additional source of jitter on the digital side, besides the jitter of the FPGA clocks and gates themselves.
Can my application be achieved by using the acquire command or must I write a dedicated C program ?
The aqcuire command has next to no support for trigger settings, but you should find it easy enough to retrofit it for your needs.
Can the acquire command be triggered with external trigger ?
see above
Are there some examples of using the SPI port to read from a slave chip ?
Newer versions of the Red Pitaya ecosystem come with a generic driver for the SPI port. There are some examples on the Red Pitaya homepage.
Are there some examples on using the spare UART serial port on E2?
Also on the homepage.
Can I toggle ( ON/OFF ) a GPIO port easily ? ( want to use this to monitor timing with a Logic analyser ).
Very (if you build upon the footwork the acquire utility already does for you).

Farren
Posts: 10
Joined: Tue Sep 15, 2015 11:07 am

Re: Radar Video Signal Processor

Post by Farren » Sat Sep 19, 2015 1:27 pm

Thanks Nils,
After making this post yesterday morning I decided to spend the day searching for examples and
info on making my own programs/process for the Red Pitay.
I had very good success and was able to run several C examples and modify them, recompile and run.
All works very well and it seems that I am going to have success with this amazing little board.
To get up and running so quickly I did the following:
Install Virtual Box on my Windows Machine.
Install and configure Ubuntu Linux in the Virtual box ( they have made Ubuntu so easy to install and use compared to 15 years ago when I attempted to use Red Hat Linux).
Installed the RP SDK and ran / modified the C examples.
All the above was fairly easy. :D
Now I would like to dig into the FPGA side of things, this will take longer....
Cheers
Farren

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