Fped GUI Manual

This manual introduces the basic concepts of Fped and explains the elements of the graphical user interface. Please refer to the file README for more technical details and a discussion of the scripting language used by fped.

Objects and instances

Footprints tend to be highly repetitive, with many pads placed in a simple geometrical pattern. With fped, the user specifies the elements to repeat and the way they are repeated. Fped then generates the repetitions automatically.

Hands-on example

Here is a simple example that illustrated the basic steps of constructing things with fled:

Start fped without a command-line argument.
Right-click on the yellow field that says "(root)" and select "Add loop". An entry saying "_ = 0 ... 0 (0)" appears next to the yellow field.
Click on the underscore, type n=1,5 and press Enter. The entry should now show "n = 1 ... 5 (1 2 3 4 5)"
Click on the dark-yellow vector icon on the right-hand side. A red frame shows that it is selected.
Move the mouse pointer to the green dot in the middle of the black canvas. A red circle appears when the pointer is over the dot.
Press the left mouse button, drag a little to the right, and release the mouse button. A white line appears and changes to dark yellow after the button is released.
Click on the yellow line. It is now shown in bright yellow and a number of text entry fields appear below the canvas.
Click into the field on the top that probably says "0.1mm", change it to n*1mm and press Enter.
Select "Zoom all" from the "View" drop-down menu. The canvas should now show the green dot on the left, with a yellow arrow pointing to the right, and four more even darker arrows following that arrow.
Click on the icon depicting a light-blue circle.
Move the mouse pointer over the green dot, then drag to the circle at the end of the vector, and release the mouse button. A series of partial circles should appear.
Select "Zoom all" again to show the full circles.

The graphical items you have entered are a vector and a circle with the radius determined by the vector. We call these items "objects". Furthermore, you have defined a variable that gets set to the values from 1 to 5, in increments of one. Fped had repeatedly drawn the objects for each such value. We call the item that have been drawn "instances".

The innermost vector and circle are highlighted. You can highlight other instances of the same objects by clicking on the numbers (1 2 3 4 5) shown next to the loop.

Conceptual view

The following picture illustrates the concept: the model is defined in terms of objects, in this case a vector from the origin to the circle's center, a vector for the radius, and the circle itself.

The vector to the center uses a variable that gets iterated through the values 0, 1, and 2. For each iteration, an instance is generated.

Only the instances of silk screen objects and pads are exported to KiCad. Elements used for construction, such as vectors, only appear in fped.

Frames

Frames serve various purposes:

To structure the footprint drawing by grouping like elements. For example, one may want to place pads, outline, and the keep-out area in different frames, and probably subdivide some of those constructs even further.
To define an element that is used in several places. For example, a pad.
To define a repetition through a loop or a table.
To set variables for child frames.

Variables

Iconography

The right-hand side of the fped window shows the component being drawn on a black background. We call this the canvas. It is surrounded by a toolbar on the right side and a few buttons with visibility options at the top.

The canvas

Blue screen

When an expression uses an unknown variable or evaluates to an incorrect value (e.g., a bare number where a dimension is expected), the instantiation fails. Fped indicates this by changing the background color of the canvas from black to blue. The cause of the failure is explained in the status bar at the bottom.

In this state, the canvas is no longer updated when making changes until the problem has been resolved. The most common causes are a misspelt variable name in an expression, the use of a number without unit where a dimension is expected, or the removal of a variable that's still used somewhere.

If the location of the error is not obvious, the list of objects can be shown by selecting "Swap var&code" from the View menu. The object in which the error occurred is shown in red. If the error occurred in a loop variable, the variable name is shown in red.

Visibility options

When working on a complex component, the number of elements shown can be overwhelming. The visibility options help to quickly hide irrelevant details and get one's bearings. They are located in the menu bar at the top.

: Show all frames. If disabled, only show the currently active frame.
: Show vectors and frames.
: Show measurements.
: Highlight the elements that will be exported to KiCad, i.e., the pads and the silk screen drawings. To show the component exactly as it will appear in KiCad, also turn off vectors, frames, and measurements.

The visibility options can be combined.

Tools

Tools are used to add new elements and to manipulate existing ones.

The pointer. This is the default tool. The pointer is used to select items and do move points of the selected item.

Clicking on an item selects it. If items overlap, the one with the highest priority is selected. The priority is based on how difficult it usually is to select an item, with frame references having a low priority, pads, circles, arcs, rectangles, measurements, and lines having increasingly higher priorities. There are a few special cases:

The circle at the end of a vector has the highest priority while its line has the lowest priority.
To select a frame reference, click on the L-shaped upper left corner.
To select a measurement, click on the line with the text, not the (hypothetical) line connecting the points being measured.

If multiple items are under the mouse pointer, repeatedly clicking iterates through them.

To move points, select the item, then move the mouse pointer over the point to move. A red circle will appear under the mouse pointer. Then drag the point to its new location and release the mouse button.

Delete the currently selected item. Whenever an item is selected, the delete icon lights up. Clicking the icon deletes the item. To undelete the item, press U.

Add a vector. To add a new vector, move the mouse pointer to the new vector's starting point then drag towards the desired end point. Vectors are normally specified via parameters. To enter the parameters, click on the new vector.

Note that the starting point of the vector has to be in the same frame as the vector being drawn. This limitation also applies to points defining pads and silk-screen items.

Add a frame reference. A frame reference inserts the content of a frame into another frame. There are three steps in this process:

Select the frame to be inserted and click on the frame icon. A large black dot appears in the icon to indicate that a frame reference has been chosen.
Select the frame into which to insert the reference. The dot changes to green to indicate that the reference can now be placed. If the dot stays black, then the selected frame is not a valid destination, i.e., because the reference in turn references this frame.
Click on the location at which to attach the reference. This location can be either the end of a vector or the frame's origin.

When finished, don't forget that the destination frame is still selected. In order to add elements to the newly referenced frame, you have to select it first.

Add a pad. Pads are either rectangular or rounded. They are defined by two points which are opposite corners of the rectangle containing the pad. Move the mouse cursor to the first point, then drag to the second point. The pad's name can be edited after selecting the pad.

Add a line or a rectangle. Similar to pads, lines and rectangles are defined by two points. The width of the line can be edited after selecting the line or rectangle.

Add circle or arc. Circles are defined by their center end a point at their radius. An arc has a third point, which defines the angle at which the arc ends. If this third point is not located on the radius, the arc ends where an imaginary line between the center and the end point would intersect with the radius.

An arc is made by first drawing a circle with the radius point at the location where the arc should start. Then click and hold the radius point to drag the end point to the desired location.

To change the radius point of a circle, first drag the end point, then drag the radius point itself to that same location.

Add a measurement. Measurements show the distance between points. They can either measure diagonally or only horizontally or only vertically. Unlike other items, measurements are not limited to points in the same frame. Instead, they operate on the minimum, maximum, and next greater coordinates of instances of objects.

A measurement is added as follows:

Click on one of the three measurement icons to select the measurement type. All possible endpoints are highlighted.
Drag from the desired starting point. Now all the endpoints available for this starting point are highlighted.
Drag to the endpoint and release the mouse button. The measurement will now appear as a double-headed arrow and text between the two points (if this is a diagonal measurement) or extending vertically or horizontally from one of the two points.
To move the measurement arrow away from the two points, select the measurement and set an offset.

Sometimes, the second point becomes unavailable after selecting the first point. This means that the two points are not a minimum or maximum, or a minimum and the next greater neighbour. In this case, just try another pair of points measuring the same distance.