By Adam Taylor

We have looked at SDSoC several times throughout this series, however I recently organized and presented at the NMI FPGA Machine Vision event and during the coffee breaks and lunch, attendees showed considerable interest in SDSoC—not only for its use in the Xilinx reVISION acceleration stack but also its use in a range of over developments. As such, I thought it would be worth some time looking at what SDSoC is and the benefits we have previously gained using it. I also want to discuss a new use case.

SDSoC Development Environment

SDSoC is an Eclipse-based, system-optimizing compiler that allows us to develop our Zynq SoC or Zynq UltraScale+ MPSoC design in its entirety using C or C++. We can then profile the application to find aspects that cause performance bottlenecks and move then into the Zynq device’s Programmable Logic (PL). SDSoC does this using HLS (High Level Synthesis) and a connectivity framework that’s transparent to the user. What this means is that we are able develop at a higher level of abstraction and hence reduce the time to market of the product or demonstration.

To do this, SDSoC needs a hardware platform, which can be pre-defined or custom. Typically, these platforms within the PL provide the basics: I/O interfaces and DMA transfers to and from Zynq device’s PS’ (Processing System’s) DDR SDRAM. This frees up most the PL resources and PL/PS interconnects to be used by SDSoC when it accelerates functions.

This ability to develop at a higher level and accelerate performance by moving functions into the PL enables us to produce very flexible and responsive systems. This blog has previously looked at acceleration examples including AES encryption, matrix multiplication, and FIR Filters. The reduction in execution time has been significant in these cases. Here’s a table of these previously discussed examples:

Previous Acceleration Results with SDSoC. Blogs can be found here

To aid us in the optimization of the final application, we can use pragmas to control the HLS optimizations. We can use SDSoC’s tracing and profiling capabilities while optimizing these accelerated functions and the interaction between the PS and PL.

Here’s an example of a trace:

Results of tracing an example application

(Orange = Software, Green = Accelerated function and Blue = Transfer)

Let us take a look at a simple use case to demonstrate SDSoC’s abilities.

Frequency Modulated Continuous Wave (FMCW) RADAR is used for a number of applications that require the ability to detect objects and gauge their distance. FMCW applications make heavy use of FFT and other signal-processing techniques such as windowing, Constant False Alarm Rate (CFAR), and target velocity and range extraction. These algorithms and models are ideal for description using a high-level language such as C / C++. SDSoC can accelerate the execution of functions described this way and such an approach allows you to quickly demonstrate the application.

It is possible to create a simple FMCW receive demo using a ZedBoard and an AD9467 FPGA Mezzanine Card (FMC). At the simplest level, the hardware element of the SDSoC platform needs to be able to transfer samples received from the ADC into the PS memory space and then transfer display data from the PS memory space to the display, which in most cases will be connected with DVI or HDMI interfaces.

Example SDSoC Platform for FMCW application

This platform permits development of the application within SDSoC at a higher level. It also provides a platform that we can use for several different applications, not just FMCW. Rather helpfully, the AD9467 FMC comes with a reference design that can serve as the hardware element of the SDSoC Platform. It also provides drivers, which can be used as part of the software element.

With a platform in hand, it is possible to write the application within the SDSoC using C or C++, where we can make use of the acceleration libraries and stacks including matrix multiplication, math functions, and the ability to wrap bespoke HLD IP cores and use them within the development.

Developing in this manner provides a much faster development process, and provides a more responsive solution as it leverages the Zynq PL for inherently parallel or pipelined functions. It also makes it easier to upgrade designs in terms. As the majority development will also use C or C++ and because SDSoC is a system-optimizing complier, the application developer does not need to be a HDL specialist.

Code is available on Github as always.

If you want E book or hardback versions of previous MicroZed chronicle blogs, you can get them below.

First Year E Book here

First Year Hardback here