Direct Memory Access (DMA) : A hands on Zynq example

DMA Tutorial : A hands-on example using Fast Fourier Transform (FFT) IP

Based on this video.

Level : Beginner +. If you come from the “begginer” section tag, please make sur you did the “implementing your own IP” tutorial (or that you have similar knowledge).

Find the example FFT DMA bare-metal firmware here

Intro

DMA is a way to access memory without using loads instructions from you CPU.

The CPU asks the DMA to handle memory transactions for him, allowing the cpu to do more valuable tasks.

You can see DMA as a “memory co-processor”

In this video, I walk you through a hands-on example to implement you first DMA on Zynq (or any FPGA if you know how to implement a softcore CPU) and how to interface it with an FFT IP as an exmaple device to leverage you IP designs without stalling to CPU to move data around.

Prerequisites

• Know the basic of Vivado & vitis (see “implementing your own AXI LED IP” tutorial)
• You don’t need to understand FFT deeply to complete this tutorial, the FFT is just an exmaple.
• Have vivado & vitis installed.

Video layout

1 : What is DMA

This first part is all about explaining what is DMA. It’s pretty straight-forward.

2 : Implementing a FFT IP (Hardware)

This part is about putting all the hardware toghther. We don not implement a custom IP but a pre-made FFT IP from xinlinx to compute fourier transforms FAST !

Given that we are not designing any IP this tutorial does not include any HDL.

3 : Implementing a FFT IP (Software)

In this part, We break down the firmware code logic and make our own firmaware so you can go on a make your own for your projects.

IMPORTANT NOTE if you plan on using UART like in the tutorial : do not use xil_printf() but rather printf() to handle the display of floats correctly.