1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/BoardOutline/README.txt Thu Feb 16 23:24:53 2017 +0100
1.3 @@ -0,0 +1,79 @@
1.4 +Files
1.5 +-----
1.6 +
1.7 +The cartridge_board_measurements.svg file was converted to the form defined by
1.8 +cartridge_board.svg by removing dimension details, setting stroke widths to 0
1.9 +for all objects, converting shapes to paths, performing a union operation on
1.10 +the main board shape with the rectangles providing material for the edge
1.11 +connector curvature (see below), then using the difference operation to remove
1.12 +all cutout shapes. This should leave a single path object defining the board
1.13 +minus the cutouts.
1.14 +
1.15 +The cartridge_board_rear.svg file takes the board shape, flips it
1.16 +horizontally, and converts all curves to lines by adding more points (three
1.17 +times appears sufficient) and then using the curve-to-line operation. This
1.18 +file is then exported to DXF (version 14) and produces the
1.19 +cartridge_board_rear.dxf file.
1.20 +
1.21 +Importing the cartridge_board_rear.dxf file into KiCad with the connectors
1.22 +aligned to a 0.127mm grid, the offsets 60.445mm (3in - 15.755mm) and 127mm
1.23 +(5in) can be used. The DXF file is suitable for designs where the rear of the
1.24 +board is the focus, typically because that is the side on which components
1.25 +will be mounted.
1.26 +
1.27 +PCB Measurements
1.28 +----------------
1.29 +
1.30 +The cartridge_board_measurements.svg file summarises the details below.
1.31 +
1.32 +ROM cartridge board width is 84.85mm, height is 62.5mm.
1.33 +
1.34 +Mounting holes are at 4.975mm and 79.875mm horizontally with small holes
1.35 +having a radius of 1.6mm and large holes having a radius of 3.75mm. Small
1.36 +holes appear at 5.875mm and 45.875mm from the top of the board (56.625mm and
1.37 +16.625mm from the bottom). Large holes appear at 36.875mm from the top of the
1.38 +board (25.625mm from the bottom).
1.39 +
1.40 +Two mounting slots of 2.2mm width are centred on 14.825mm and 70.025mm
1.41 +horizontally. The front left (rear right) slot starts at 23.475mm from the top
1.42 +of the board (39.025mm from the bottom) and ends at 35.575mm (26.925mm), then
1.43 +being extended by a circular cutout of 1.1mm radius. The front right (rear
1.44 +left) slot starts at the same vertical location but ends at 33.075mm
1.45 +(29.425mm), being extended by the 1.1mm radius cutout. Thus, it is 2.5mm
1.46 +shorter.
1.47 +
1.48 +Edge Connector Pads
1.49 +-------------------
1.50 +
1.51 +Edge connector width is 56.5mm, height is 11.85mm.
1.52 +
1.53 +The edge connector on the Advanced Computer Products cartridges (and
1.54 +presumably the Acorn ones) curves into the lower edge of the main board area.
1.55 +This curvature has a 1.1mm radius.
1.56 +
1.57 +AppNote-014.pdf indicates that "Cartridges plug into a 44 way gold plated edge
1.58 +connector arranged on each side of a 0.05 inch slot as 22 ways of 0.05" x 0.5"
1.59 +on 0.1" centres."
1.60 +
1.61 +Note that 2.54mm = 0.1in. Thus, "0.1" centres" indicates a spacing of 2.54mm.
1.62 +The connectors are therefore 1.27mm x 12.7mm. The slot is 1.27mm (0.05in)
1.63 +wide, presumably requiring such a board thickness.
1.64 +
1.65 + 1.58mm margins from the edges to the centre of the first connector
1.66 +
1.67 + 2.54mm between the centres of each connector
1.68 +
1.69 + 22 connectors gives...
1.70 +
1.71 + (22 - 1) * 2.54mm + 2 * 1.58mm = 56.5mm
1.72 +
1.73 +The edge connector has an offset of 14.175mm from the left edge of the board.
1.74 +
1.75 + (84.85mm - 56.5mm) / 2 = 14.175mm
1.76 +
1.77 +The first connector has an offset of 15.755mm from the left edge of the board.
1.78 +
1.79 + 14.175mm + 1.58mm = 15.755mm
1.80 +
1.81 +The base of the connectors has an offset of 62.5mm from the top of the board,
1.82 +being the base of the board.