Synthesizer

In October, 2014, we did a pair of PCB layouts for an analog synthesizer for music recording. This design is a basic demonstration of the superior capabilities of Altium Designer over CadSoft Eagle. The simple fact is that a project like the FPGA-DDR3 board we designed before this is impossible to do in Eagle, whereas a basic project like this is merely painful to do in Eagle.

Our client provided us with his schematics in Eagle format. Altium’s Eagle importer works very well for both schematics and PCB’s. Eagle allows placement of designators in the library, but Altium does not, so the redundant designator fields appeared as dots in the schematics which were somewhat difficult to eliminate.

Very few changes were made to the client’s schematics, but switching to a heirarchical structure would have improved the relatability of the net identifiers between similar sheet modules in the design and also avoided potential naming conflicts. Eagle V7 only just implemented heirarchical design which has been in Altium since at least 1994 when I started using Protel. The real issue with Eagle isn’t how they’re just catching up to Altium’s most basic features, it’s the extremely poor user interface.

Our client provided a PCB file with board dimensions and positions of the panel controls. Slot holes in the PCB were imported as polygon shapes with just round holes which needed to be corrected, but per my habit the symbols were completely verified against datasheets. Altium imported all of Eagle’s extraneous layers as mechanical layers. There seemed to be hundreds (numbered up to 255) of layers to search through and delete the junk objects on them (this is actually much worse to deal in Eagle itself which has no way to disable or hide layers or to tell if anything is even on a layer). The ratsnest was imported on one of the mechanical layers as lines which had to be deleted, but this was not apparent at first because, you know, they deceptively look like the ratsnest.

The main PCB is a 4-layer design intended to minimize crosstalk between the various analog modules. The layout was not especially challenging except for the need to route so many signals to banks of header strips connecting to the control panel which caused lots of contentions. The panel PCB is extremely basic, consisting of the user interface components: jacks, switches, sliders, and dials. The headers could only be placed in gaps between the controls, which consequently restricted the layout of the main board.

After completion, the client requested the files to be converted back into Eagle format. Eagle can import the Altium PCB if you save it in ASCII format first, which you can only do if you have a license for Altium, which our client does not. Eagle really needs to stop treating the old P-CAD file format as current. Eagle could not import the Altium 14 schematics at all unfortunately. The importer is not even up to date on the nearly decade out of date P-CAD schematic file format.