centroid file top and bottom orientation differ by 90 degrees
I am using PCB version 1.99z. I have attached a small double sided example pcb with one component on each side. The file->export->bom xy-file is:
# RefDes, Description, Value, X, Y, rotation, top/bottom
# X,Y in mils. rotation in degrees.
The locations are correct but the top is rotated 90 degrees wrt the
I think the "heuristic" approach to determining the device orientation in the gEDA pcb code is mistaken (see src/hid/bom/bom.c and pcb.pdf section "E.3 Computation of Centroid and Rotation"). The orientation is assumed to be that between pins 1 and 2. Unfortunately, IC manufacturers are not consistent in the orientation of these pins. For example in one of my designs I have DIL pin-outs like:
and 4-sided SMT packages like:
3 2 1 20 19
144 143 142
ScreamingCircuits gives a guide to its expectations of device orientation in a centroid file in "http://
To do centroid output reliably, gEDA pcb should maintain an internal record of the rotation that has been applied to each footprint.