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When Projects Should Be Cloned to a New Revision

PCB revision

When EE's start working in larger organizations, or they just accumulate a large archive of past projects, they most likely start using a version control system. One of the great things about a version control system is that it can be used to track change histories in a project. As changes are made and committed to version control, designers can roll back or roll forward as needed without needing to store past copies of a project.

However, at some point a new archive could be created based on a major change in the design. When a major change occurs in the engineering requirements or functionality, and it is being implemented in the design, the project might be cloned into a new revision.

Version control systems will track all of this in a single project, as well as in clones of a project which are assigned new revision numbers. Here are some of the times you might be expected to roll a project to a new revision.

Revisions Are Not Always Version Control Entries

While it may be highly recommended that you use a version control system, cloning a project into a new revision is something that can happen in addition to each commit into version control. Inside of a version control system, each commit is sometimes called a revision and is tracked as a change history in a project. Revisions in hardware development are tracked independently, and they are typically tracked as separate projects. If files are being tracked on a local computer or server, each revision is its own set of files that is tagged with the correct revision number and time code.

To designate a revision, projects will typically be tagged “Rev A” or “Rev 1” to denote the first revision of a project. The choice of revision numbering or lettering is really a designer's personal decision or a company policy. Each of these revisions would have its own version history showing changes committed to version control. Some librarians or managers might prefer these to be forks or branches of an earlier revision. The typical version history flows shown below.

 PCB revision

At some point along the course of a project, there may be some changes that necessitate creating a new revision in this long chain of version control system entries. Here are some of the reasons you might create a clone and call it a new revision.

Changes After a Prototype Build

Oftentimes following a prototype build, the board will be tested and it may be found that certain changes are needed. This is a typical time to take a design to a new revision and implement the changes within the new revision.

The scope or extent of the changes is not what drives the need for a new revision. Instead, the prior revision is taken as a reference for the most recent good version of a design. Even if small changes are made to the design, this could create non-negligible changes in functionality, and the new version of the board will be taken as the newest and the best working version of a design. In this case, we would want to clone from the prior revision into a new project, and the newly cloned project would be given the newest revision number.

After Sending For RFQ

When a design is sent out for RFQ, the contract manufacturer or fabrication house should track each version of a design they receive under quote requests. Most commonly, they will do this using your revision number and part number. While it might seem like unnecessary accounting, there are some good reasons for doing this:

  • There can often be rounds of questions which lead to changes in the production files

  • Each set of production files needs to be tracked and associated with a quote

  • Client-provided revision numbers are a simple piece of information that both parties can use to track a design

At each stage during an RFQ process, the manufacturer might demand files be rolled to a new revision as questions are received and answered, especially when changes are made to the design data.

System Architecture Changes

Finally, it is also possible to roll to a new revision when some portion of the system architecture changes. This is somewhat less common, and the idea of a system architecture change is rather ambiguous. There is really no required scope change that would demand rolling to a new revision of a design. Instead, this could be more of a data management driven decision based on company policy, or based on new or modified engineering requirements.

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