hdl

During the work on merging #1419 I figured out that the basic BUFGMUX example works differently on Arty Board and Nexys Video.

The example uses three LEDs:

• led[2] - blinks with slow frequency
• led[1] - blinks with high frequency
• led[0] - blinks with the same frequency as led[2] or led[1] depending on sw[0] state.

On the Arty Board, the example works as intended. On Nexys Video, when

Motivation

It doesn't make sense for a signal to be driven by two drivers in a Sequential block. The code already prevents this, but testing is incomplete.

Desired solution

Add a test ensuring that an exception is thrown when there are multiple drivers for a flop.

Here are some "nice to have" feature requests for the cool new "Compared test results" output that has been recently added.

• Colors! It would be nice to highlight;
  • Improvements in green
  • Regressions in red.
  • Non-changes de-emphasized in light grey.
• Link to the published version of the before and after results so people can understand exactly

It would be nice if the Hardware Description Languages section mentioned simulating tooling like:

• iverilog
• gtkwave
• verilator

A few things that I wish I learned from the workshop rather that "discovering/googling" by myself:

• use iverilog as a linter (seems to be more pedantic that yosys).
• how to create testbench
• how to $monitor variable
• gotcha to create / optimize vhd fi

Together with issue #4, we should write a few tests for making sure refdeses do stay consistent. Something like a copy of servo_micro, and a ton of patches on top of it (all parented to one servo_micro, not on a chain, more like a star). Apply each of those patches then see if refdeses are sticking.

git checkout c718fbc~1 examples/servo_micro.py from google/pcbdl@ba3