Upgrade your Pineapple PCB designer with the latest autorouting facility. Geoff Bains reports.
PCB Autoroute (Pineapple)
The biggest bugbear of designing a printed circuit board is actually deciding where all the copper tracks must go to make the connections needed, without crossing over each other or attempting other such impossibilities.
Although a software package such as Pineapple's PCB (see Beebug Vol. 5 No. 8) is a great help to board designers, it still leaves the real decision making up to you. PCB is essentially only a specialised drawing package. Now (and somewhat miraculously) PCB autorouting has come to the BBC micro in the form of an add-on package for Pineapple's PCB.
PCB Autoroute is, like PCB itself, in ROM. It interleaves with the existing PCB program perfectly. When you get to the tracking stage of designing a board, a function key is pressed to enable the new software addition.
Now you enter the connections to be made. This is all done visually. From each component lead (already marked on the board with a solder pad) the cursor is used to rubber band a line directly to where that pad is to be connected. This doesn't have to be another pad - it could be just an empty point on the board or, more likely, to join onto a 'bus' of connections.
At this stage some intervention can be made on the forthcoming automatic course of events. Each connection can be biased towards the topside or solderside of the board, or with equal preference for either. You can also bias the connection from the start point in a particular direction (entered as compass directions NE, NW, SE and SW) so as to start off the autorouting algorithms in the correct direction.
There is nothing to stop you entering some tracks completely by hand, either at the start or half way through the interconnection defining. You just switch back to the routing stage of the normal PCB program and take it from there.
The interconnections can be easily edited too and they are all stored on disc like all other stages of the design process, so you do not have to finish it all at one sitting - very useful for complex boards which get a little mind-boggling after staring at the screen for a while. You do have to be pretty methodical when making the connections or you get in a terrible mess with nothing more useful than a spaghetti picture on the screen. However, if you are logical and ordered about the whole procedure it is simple enough. Once all the desired connections are made, another function key is pressed and the software gets on with it. The autorouting process takes anything from 30 seconds to a few minutes depending on the complexity of the board, but it draws tracks as it goes along so it is great fun to watch. When it is finished, it reports connections it cannot complete, which can be simply highlighted to be altered or drawn in by hand.
PCB Autoroute will not solve all your PCB design problems - it does require both careful thought beforehand and a fair amount of tidying up afterwards. Although it appears expensive, there is nothing else remotely similar, even on other micros, for less. Many would have said it couldn't be done but it just goes to show there is life in the old Beeb yet.
1st April 1988
