Astrocade Interface – Building the PCB

Whether you got a kit of parts or a PCB and sorted out the necessary parts yourself, you now need to put it all together, test it and get it up and running in your cabinet.

This sequence is putting together one ready for use in a Gorf cabinet, there is a difference if you are using it in other cabinets, but it mainly means populating different areas and I will mention that at the end. The board here is V2.2, but nothing (visible) changes for V2.3

I usually start with the shortest components and work up, so that means I commence by putting all of the resistors in first. Since this is going to be for Gorf, the area in the middle has been populated as well. (marked Gorf Only) – This section controls the ranking lights and the light in the joystick.

Next I have added the sockets for the TTL chips, the Daemonbyte controller, the connection to the DE10-Nano, the connection for the RGB Daughterboard and the OSD button. (to bring up the on screen display in MiSTer). There is also a couple of pins that you can use to extend this button elsewhere in the cabinet if you wish.

Now I add all of the capacitors and transistors. As you can see the area middle right (marked WOW only) is left clear, this provides the third audio channel for Wizard of Wor which none of the other games use.

All that is left to add now is the pins to connect to the cabinet loom to (Power and controls / outputs). As this PCB is for a Gorf cabinet, we have put the pins in the Gorf row. (If you are doing one of the other games, then you must populate the row relevant for that game.) I recommend using pins at least 17mm long for the control connections, the original connectors need the extra length to stay in place.

Power options

There are 4 ways that you can power the DE10-Nano once it is in the cabinet. The first of these is to simply use the PSU that came with the DE10-Nano and connect it to 110v / 240v as required. In this case you do not need to change anything on the PCB and leave all of the power option area blank. The power still needs to be connected as the board needs a common ground for the controls to work. It also uses 5v from the cabinet to power the Gorf lamp outputs.

The second is to use the 5v supply direct from the cabinet. To enable this simply add a solder bridge to the pad marked Direct 5v (just above the 6 pin socket). I would only do this personally for a cab that has had a switcher fitted, but if you have confidence in your PSU, then this can be done.

The third option, which I have used most, is to install a 2 amp version of the 7805 and two capacitors. I have used K7805-2000 and R-78K5.0-2.0L – the latter usually being cheaper to obtain. This generates 5V for the DE10-Nano from the cabinets 12V line.

The final option is to use a commonly available LM2596S DC Buck Converter PCB. These are frequently listed on ebay. Just make sure you line up the ins and outs accordingly. These are adjustable so make sure that you set the output voltage to 5v BEFORE connecting up the DE10-Nano. The last ones I purchased came pre-set for 9V. This also generates 5V for the DE10-Nano from the cabinets 12V line.

Completing the main PCB

Finally, if you used one of the on board power options you need to install the lead to the barrel plug. This should be centre positive. It is also the time to fit the TTL chips and the Leonardo pro that you have programmed the Daemonbytes software into.

Here are two completed boards, the one on the left is for Gorf and the one on the right is for Wizard of Wor. You can see the difference in which areas have been populated.

RGB Interface PCB

This is the easy one, it simply converts the 6 pin IDC extension from the main PCB to the normal 9 pin connector used as the output from the Astrocade RGB PCB. You just need to solder a 6 pin IDC socket and some long pins. The section on the right is to generate a composite signal for use on a black and white monitor in some Space Zap cabinets.

Safety Check

Before connecting everything up I always perform a few checks to make sure I haven’t made any mistakes and that the important bits are working as expected. Apart from the 5v line to the barrel plug, there should be no way that power can pass from the interface PCB to the DE10-Nano, so I check that this is the case.

Connecting just the power block from the cabinet I power it up. Using a logic probe, I check all 40 pins of the IDC socket to make sure that nothing has power applied to it, everything should be floating or GND.

Then I check the power out on the barrel plug (if you are using the on-board regulation or direct DC option) with a meter. This should measure 5v centre positive.