Page 224 - Make Your Own PCBs with EAGLE from Schematic Designs to Finished Boards

CHAPTER 10

Commands, Scripts, and User-Language

Programs

S ometimes, when designing an electronic project in EAGLE, you will come across activities

that are repetitive or that you seem to need to do for every project you start. It would be nice
to be able to automate such activities and save yourself some time.

Fortunately for us, EAGLE includes technology to do just such automations. Scripts are simple
lists of text commands to be invoked and are useful enough. However, EAGLE also includes a user-
language program (ULP) language. This is a fully featured programming language that allows you to
branch off and do different things under different circumstances or repeat certain instructions a
number of times in a loop. For example, later we will look at how you can use a ULP to automatically
smash all the parts on a schematic.

Ultimately, whether you use a ULP language or a simpler script, the end result will be the
invocation of commands, and it is here that we will start.

Commands

You may have noticed the command line beneath the toolbars. You can type commands here that do
the same things as you can otherwise accomplish using your mouse. Figure 10-1 shows a command

ready to be run.

FIGURE 10-1 Entering commands.

Start a new project with a schematic, then enter the command add R-US_VMTA55@rcl (0
0.1), and then hit “Return.” You will see a resistor appear just above the origin. Let’s now examine
this command.

The command is Add, and this can be specified in uppercase or lowercase—it doesn’t matter.