PYNQ, Partial Reconfiguration

Environment

PYNQ v2.7, Z1 board, Xilinx 2020.2 tools

Tutorial

I’ve noticed that this tutorial goes over Partial Reconfiguration(PR) on Pynq environment and verified that it’s working in PYNQ v2.7. The related code is in the video’s description.

.tcl Files

One unclear thing was that if we do make dynamic, it calls create_pr.tcl, and in create_pr.tcl it requires led_0.tcl, led_5.tcl, and led_a.tcl. The tutorial above covers how to generate these files starting 20:42, but I think it needs a bit more elaboration.

First, double click the hierarchical block in Vivado’s block diagram view, and it will display components inside the hierarchical block. Right click and select all. Then, Create Block Design to create a seperate led_0 block diagram. Right click and paste them all. Do the same for led_5 and led_a. You can either File→Export→Export Block Design or select Generate Block Design to get led_*.tcl files.

.hwh Files

PR in PYNQ requires not only .hwh file for the full bitstream but also .hwh file for each partial bitstreams. Previously, it was either .tcl or .hwh, but in v2.7 I think only .hwh works.

.hwh file is auto-generated when we do Generate Block Design. (or rightclick the block diagram and generate output products. They are the same things. FYI, this is automatically done when we do synthesis with launch_runs synth_1.) You can check where .hwh files are located with find . -name "*.hwh".

Therefore, to facilitate PR in PYNQ, we are kind of forced to create block diagram in Vivado. However, we are not forced to use Vivado Project Flow to do PR. In Project flow, we create “child implementation runs” and launch_runs impl_1 does update_design -black_box and lock_design -level routing, etc under the hood. The tutorial above also does it in this manner. But explicitly generating static design with finer-grained commands mentioned above also works.