Foundation Series 6: Vivado Automation with TCL

Tcl is a core part of the Vivado Design Suite. Vivado workflows can be automated in both Project Mode and Non-Project Mode, while Tcl commands can be executed interactively through the Vivado Tcl Console or automatically in batch mode. Tcl helps determine which design data should be used at a particular stage, when that stage should be executed, and what actions should be performed after it is completed. Therefore, Tcl acts as an orchestration language for Vivado automation. Instead of manually performing every design step, engineers can use Tcl scripts to execute the same operations without user intervention. This makes the design flow repeatable, reproducible, and easier to maintain. Automation also reduces the possibility of human error caused by missed settings, incorrect file selection, or inconsistent execution of design steps. Whether you are a design engineer or a verification engineer, you frequently need to repeat specific operations. For example, if a design fails during implementation, you must analyze the problem, correct the design, and execute the required steps again. Instead of repeating these operations manually, you can build a script that controls the complete FPGA design flow and execute it whenever necessary. Iterations involving RTL or testbench code are frequent during the debugging and product-development phases. A small modification may require elaboration, synthesis, implementation, timing analysis, simulation, or report generation to be repeated. Tcl automation can significantly reduce the effort required to perform these repetitive tasks and allow engineers to spend more time analyzing results and solving actual design problems. Regression testing is especially common in verification roles. A script that accepts multiple test cases and executes a complete regression can be used for nightly builds and integrated into CI/CD pipelines. It can compile and elaborate the design, execute multiple tests, assign different random seeds, control simulation runtime, collect logs and waveform files, identify passing and failing tests, generate summary reports, and return an appropriate status to the CI/CD system. Most engineers have some knowledge of Tcl, and many resources are available for learning Tcl fundamentals. However, using Tcl to automate an engineering flow requires a different set of skills. Knowing individual commands is not enough; engineers must understand how to connect design stages, validate inputs, handle failures, preserve results, and make the complete flow reusable. This requires us to think from an automation and DevOps perspective rather than only from the perspective of a design or verification engineer. This course is developed from that viewpoint and focuses specifically on the role of Tcl in Vivado automation. The objective is not simply to teach Tcl commands, but to demonstrate how those commands can be combined to solve practical FPGA-development problems. With the rise of AI agents, automation engineering is becoming increasingly important. Automation engineers use Tcl to control EDA tools and may use Python to integrate engineering workflows with external systems and AI agents. The automation architecture taught in this course can therefore be extended toward agentic AI-based FPGA development flows, where agents initiate builds, analyze reports, detect failures, and recommend further actions. The course begins by explaining how Tcl can automate Vivado project creation and validate the required environment and configuration. This includes checking the Vivado version, Tcl version, target board, FPGA device, current project state, build mode, and build directories. These checks help prevent the flow from continuing with an incorrect or incomplete configuration. You will learn how to work with a persistent local-build mode for continuous development and a clean-build mode for reproducible builds and CI/CD pipelines. Local mode preserves an existing Vivado project and supports frequent design iterations, while clean mode removes previous build data and recreates the project from a known starting point. We then discuss the different Vivado filesets and learn how to access and control their properties. This includes managing design sources, simulation sources, constraint files, IP sources, compilation order, top modules, and simulation settings. Automating these activities makes it possible to recreate a project consistently on another computer or build server. Next, we study Vivado’s object-based design model and understand how to interact with objects such as projects, filesets, source files, runs, ports, pins, nets, cells, clocks, and IP cores. Understanding this object model is essential because most Vivado automation commands operate on design objects rather than ordinary text values. This knowledge also enables scripts to inspect the design database, modify properties, and extract useful implementation information. The course then explains how to automate simulation regressions and control XSim settings. This includes compiling and elaborating the design, selecting tests, passing simulation options and random seeds, controlling simulation runtime, recording waveforms, collecting logs, detecting test results, and generating regression summaries. We also examine the sanity checks that should be performed during design elaboration before synthesis begins. A well-designed automation flow must do more than start tool operations. It must detect whether each operation completed successfully, clearly distinguish design failures from infrastructure problems, preserve useful debugging information, and return an appropriate status. For this reason, the course emphasizes validation, error handling, logging, result collection, and machine-readable exit codes throughout the automation flow. You will learn how to select and modify synthesis and implementation strategies and directives, control individual build stages, and apply incremental synthesis or implementation techniques where supported and appropriate. The course also covers timing analysis and the generation of timing reports, including timing summaries, clock reports, setup and hold analysis, critical-path analysis, and the extraction of important results such as Worst Negative Slack (WNS) and Total Negative Slack (TNS). During elaboration, synthesis, and implementation, we will examine the Vivado design at different abstraction levels. You will learn how to inspect and work with ports, pins, nets, cells, slices, LUTs, flip-flops, BRAMs, BELs, and other FPGA resources. This will help you understand how automation scripts can analyze the design database, identify problems, verify design assumptions, and generate useful design and implementation reports. The course concludes with hardware automation using Vivado Hardware Manager. This includes connecting to a hardware server, discovering target devices, assigning bitstream files, programming one or multiple FPGAs, refreshing device status, and verifying whether programming completed successfully. This extends the automation flow beyond bitstream generation and into final hardware deployment. By the end of the course, you will understand how to connect project creation, source management, simulation, regression, synthesis, implementation, timing analysis, report generation, bitstream creation, and hardware programming into a structured Vivado automation flow. These skills can be applied to individual FPGA projects, engineering-team workflows, nightly regressions, build servers, and FPGA CAD or design-automation roles. Together, these topics cover the essential Vivado automation activities that can be performed using Tcl. Complete CI/CD pipeline examples and supporting scripts are also planned to demonstrate how these individual automation stages can be combined into a fully reproducible FPGA development workflow.