Propeller Development Kit

How to make a Propeller Development Kit

Read through the instructions carefully before attempting. Also read the disclaimer.

I needed a Parallax Propeller Development Board so I could keep working on my projects. Having to pull out my only prop from the pinball machine to test circuits was slow. I looked into getting the Gadget Gangster which lays out the propeller in a form familiar to those that have worked with the Arduino boards and has “shields” being built for it.

However at the time of this writing it was out of stock and I needed the board quickly so I decided to build my own on proto board. The Gadget Gangster is built off a .1″ pitch so copying the layout was easy to do on proto board. I decided that the Dev Board I would make would be much more flexible as I can add on more standard features like an Analog to Digital Convertor without having to add a shield.

I looked up a couple schematics and layouts which I have included below.

Gadget Gangster PCB Layout
Gadget Gangster PCB Layout 2
Gadget Gangster Full Schematic
Propeller Proto Board Schematic – Refer to Pg5.
SD Card Pinout – Not mine, found it on the web.
SD Card Pinout 2 – Look at SPI mode.
Interfaceing a SD card with the propeller

Besides VDD and VSS on the SD card every data line (CLK, DO, DI, RSV) should be pulled up to VDD with a 10k resistor.

Here is a incomplete parts list for the project. It just includes all what you will need. Some stuff like capacitors are not on the list as I had those on hand.

Digi-key Part #’s

1 – P8X32A-D40-ND – DIP Propeller
1 – 101-00405-75-ND – SD Card Slot
10 – CF18JT10K0CT-ND – 10kOhm Resistors
1 – 24LC512-I/P-ND – EEPROM
1 – LM2937ET-3.3-ND – 3.3V Regulator
1 – XC1711-ND – 5Mhz Crystal
2 – S7014-ND – 14 Pin Female Headers
2 – S7002-ND – 4 Pin Female Headers

Some things you will also need. I had these on hand so I don’t have part numbers.

3 – 100uf 16V Capacitors (Electrolytic)
2 – .1uf 50V Capacitors (Ceramic)
1 – Power Connector
1 – Power Switch
1 – 7805
1 – Power LED and Resistor to match for +5V source
1 – Normally Open Tact Switch
1 – 4 Pin Male Right Angle Header

You will also need a 7-12V DC power supply that fits the power jack. I used a Sony 9V DC supply that I had lying around.

This Dev Board also needs the Prop Plug for the USB connection. This can be used over and over again so if you are planning on making several Propeller projects then it is cheaper to go this route.

I would suggest you build the power circuit first and test it with a multimeter to make sure it is operating correctly before hooking it up to the microcontroller. This ensures you don’t ruined your $8 part and have to wait 4 days for the replacement to come in.

For the proto board; Radio Shack sells really inexpensive proto boards. For $4 they sell there 4″x6″ which is what I used for this project.


Don’t sue me for doing something stupid

I cannot be held responsible for any damages that could occur to you, your equipment, your property, or your electronics while following the procedures present on this website. Any acts of God(s) or stupidity caused by you is not my fault or problem. Please note that the procedures on this site have worked in my case without any damages or problems. I do not support any of the modifications on this site with any kind of guarantee.

Creative Commons License
All work on this site is licensed under the Creative Commons Attribution-ShareAlike 4.0 International License unless otherwise noted.
The Longhorn Engineer is copyright (c) 2022 to Parker Dillmann.

Sega Neptune

How to make a Sega Neptune

Read through the instructions carefully before attempting to start this project. Also read the disclaimer.

This guide is sponsored by Super Fighter Team.

The first Neptune I built can be found here. Since then I have updated the design to require only one power supply. The Genesis 2 and 32X module can run off of 650mA which is under the 850mA that the stock power supply offers. You may wonder why Sega didn’t just have the 32X draw power from the cart slot or just have a jumper cable running from the back of the Genesis power supply to the 32x? Well the cart slot can’t power the amp hungry 32x but I don’t know why Sega went with a separate power supply over a just a splitter/jumper.

This guide is a step by step overview of how to make a Sega Neptune that only uses one power supply and features region mods. This project may look daunting but it is fairly simple and straight forward. There are no supper tricky soldering situations (unless you do the region mods) so anyone that has moderate experience with a soldering and desoldering iron can build a Neptune.

Sega Genesis 2 with a 32X module on top. Our goal is to squeeze all that into the Genesis 2 case.

For this project you will need the following tools

  • Soldering Iron – 15W-25W
  • Desoldering Iron – 25W
  • Needle Files
  • Assorted Screwdrivers
  • Dremel like tool with Cutting Discs
  • Needle Nose Pliers
  • Hot Glue Gun

Parts Needed

  • Sega Genesis 2
  • Sega 32X
  • Lots of Ribbon Cable
  • 3 DPST Switches (for region mods)
Back of the 32X.

First start by disassembling the 32X. There are a lot of screws so make sure to get them all. Some are hidden on the vertical part of the 32X so make sure to get those too.

Top off of 32X.

After taking the top off the 32X remove all the screws holding the RF shielding and 32X board to the casing.

With all the screws gone the vertical portion of the 32X should slid through the bottom casing. The sides of the vertical portion should then be removed.

Flip the 32X over and find these tabs near the underside of the cart slot. Straighten them out with pliers and flip the 32X back over.

Take a small flat head screw driver and pry the RF shielding off the 32X cart slot. Make sure to be careful and not slip as damage to components and traces can occur.

There are two white ribbon cables that connect the two 32X boards together. Take these ribbon cables off by pulling them straight out of the slots that hold them in place.

Using a hammer, smash the ring to remove it. This ring is used to help prevent data corruption over the ribbon cable and please the FCC but the 32X seems to work fine without it and the 32X needs the space to fit inside the Genesis 2 case. After removing the ring replace the ribbon cables back into the slots on the 32X.

Using a desoldering iron remove the video output from the 32X. Don’t force it as you will have to use this part again. When removed take the metal shielding around it off.

Video output removed and shielding taken off.
Reattaching the video output jack.

Solder some wire about 6 inches long to the video output contacts. I used standard ribbon cable wires for it.

Then take those wires and solder them to their corresponding points on the jack. Its a good idea to test the 32X now. If it fails to work make sure you haven’t bridged a connection anywhere.

Now to disassemble the Genesis by removing the 4 screws that hold the Genesis 2 case together and take the top off.

Take the cart flaps off the underside of the top of the case by removing the 3 screws that hold it in place.

Now remove all the screws that hold the Genesis board to the RF shielding and case.

Some boards have different layouts. This one has the 7805 voltage regulator and filter capacitor right next to the cart slot so it will have to be relocated to the back of the case. If the board has the 7805 located at the back of the board skip the relocation of the 7805 and large capacitor.

The offending 7805 and capacitor.

Flip the board over to the bottom and desolder the 7805 and capacitor. Pay attention to how both where orientated on the board.

Reattach the 7805 by soldering 3 wires of about 4 inches in length to the 7805 and the board. Make sure to get the orientation of the 7805 correct. Use a heavier gauge like 20 AWG for this.

And do the same for the large cap.

Location of the capacitor. Pay no attention to the 7805 as I found a better location for it.

Now flatten the capacitors on the board to reduce the overall height off the board. Just heat up the contacts and pull them slightly to extend the leads a bit then fold the capacitor over. Be careful not to pull the traces off the board or rip a leg off a capacitor.

Now for the tricky part. Desolder the 64 contacts to remove the cart slot on the Genesis board. However, the cart slot won’t come off the board without removing some rivets.

Bottom of rivets
Top of rivets

To remove the rivets take a small flat head and position it like shown above. Push the edge inward. Be careful not to slip.

Edges of the rivet pushed in.

Then take a Philips head screwdriver and push the rivet out of the board. The cart slot should come free from the board now.

Clean the contacts on the 32X by rubbing some fine steal wool on them. This removes the oxidized layer on the metal and makes soldering easier.

Tin the contacts on the 32X. Make sure to use plenty of flux.

Connecting the Genesis to the 32X!

Using ribbon cable attach the 32X to the Genesis. The wires closest to the front of the Genesis need to be cut at 4″ and the other row needs to be 3.5″ in length. This will ensure that the wires are straight and untangled.

On the far side of the 32X the wires need to be attached upside down. When the 32X is folded down on top of the Genesis these wires will lie straight. I should have taken more pictures of this part but my first Neptune I built has some pretty good pictures of this part Neptune. I used thicker wires in that version but the method is the same.

Make 3 aluminum shields. I think I made them 3.75″ by 4″. They are 4 layers thick and covered in packaging tape to prevent short circuits. These help separate the two sets of wires and help prevent cross talk.

Place one in between the two sets of wires and one on each side of the wires like a sandwich. This is a good time to see if the Neptune is working. If it fails double check every connection and inspect the board for solder spills.

Solder some wires to the contacts shown. I cut my wires to be 7 inches long. This is to replace the cable that connects the Genesis A/V out to the 32X A/V in. Attach some heavy duty wire (18AWG) from the power input on the 32X.

Now desolder and remove the video output on the Genesis board. Then attach the wires from the 32X to the exact same spots on the Genesis video output. Make sure to solder to the bottom of the board and leave the top clean. Then attach the power wires from the 32X to the input on the Genesis.

Now take the Video output from the 32X and hot glue it upside down to the old spot of the Genesis video output. The port may be a little high so file down the hole to make it bigger.

Back of the Genesis. Ignore the fact that the power plug is missing...

Double check every connection and test the Neptune. Remember to inspect the board carefully for solder spills. If it doesn’t work the problem most likely lies with your 32X/Genesis cart connection. Check to make sure the wires are straight and untangled.

If region mods are wanted this is the time to do them. The mods are everywhere on the net so I won’t post on how to do them. MMMonkey has a really good guide on MD2 mods and for the 32X head on over to here. The 32X one is in french but google translates it pretty well. I used the simple version. I attached the switches to the back of the Genesis casing.

Location of region mod switchs

Bend the 7805 so it lies on in this corner. You may have to bend the bottom RF shielding to get it to fit.

Can't play doom yet.

Genesis games are smaller then 32X games the cart slot needs to be widened. Place a 32X cart on top of the slot and trace around it with a pencil. File down the plastic till it fits.

Can play doom now!

If you have an import JPN game you will have to cut some more of the cart slot. Use the same method.

Modified cart flap doors.

If cart slot flaps are wanted take the cart slot mechanism from the 32X an cut it down like shown above.

Hot glue these flaps to the inside of the Genesis 2 case.

Use #4 1″ wood screws to attach the 32X to the genesis board and casing. The holes around the 32X cart slot will line up with the holes on the Genesis board. Go ahead and test the Neptune to make sure it works.

Side view of the PCB sandwich.

Place the cover back on the Neptune and test the cart flaps if you have them installed. Most likely the flaps will hit the cart slot. If so cut off the edges of the cart slot with your dremel.

Put the cover back on the Neptune and replace the 4 screws. It is now done.

Some final pictures.

Beggar Prince by Super Fighter Team.
Plays any region!

A special thanks goes out to Super Fighter Team for sponsoring this how to!

A/V Install Guides

Guides for the Atari A/V Mods

Read through the instructions carefully before attempting. Also read the disclaimer.

Atari 2600

Kit Install Guides

Assembling a 2600 Kit. V2.2E
Assembling a 2600 Kit. V2.2F – Current Version

Schematic NTSC V2.2F
Part List NTSC V2.2F
Schematic PAL V1.0
Part List PAL V1.0

Atari 7800

Kit Install Guides

Assembling a 7800 Kit. V2.1

Schematic NTSC V2.1
Part List NTSC V2.1

Printout and Drill Template


Reset Vector – The circuits have turned to glue man

This will be my first pinball machine to custom build. Everything will be custom built down to the programming. For the majority of the parts I bought a broken Pinbot pinball machine and removed the working parts. Other parts are sourced from ebay or pinball conventions.

The virgin plywood and its journey into the greatest pinball machine ever to grace mankind.

The old coin door. Its pretty beat up so I will be stripping the paint off with a brass wire brush and then repainting it.

Side rails and topper bracket is installed.

Close up of the topper bracket. I took it off the old Pinbot cabinet as it was still in decent shape. Had to sand it down and fill in some holes tho.

This is the hold down bar bracket. The hold down bar is the piece of metal that locks on the top of the front. Removing it allows you to remove the glass.

Cutting the opening for the coin door.

After painting with some hammer-on finish spray paint. I chose a silverish paint to match the stainless hardware better. The legs of the machine will be painted the same color.

Cutting the test playfield out of cheap pine plywood. Using a test playfield will enable me to test shots and move parts around without worrying about drilling and cutting the playfield. The final playfield will be made out of birch plywood.

Heres what it looks like with it installed in the new cab.

Installed the coin door.

Flipper buttons installed. They use leaf switches as these are directly in series with the flippers so the need to handle 50VDC and 3-4 amps.

Powersupplies and the flipper solenoids are installed.

The powersupply setup. The left one is a 50VDC powersupply and the one on the right is a computer powersupply that will supply the 12V, 5V, and 3.3V for logic.

Put the legs on. Won’t repaint them till its out of the shop so the paint doesn’t get chipped.

Bracket for the legs. I chose to use the heavy duty variety as a couple modes I have planned require you to tilt the machine.

How the layout of the head unit will work out. The score wheels are the “roll over digit”. Basically when you hit 9999 the machine will “lockup” in blue screen of death mode. To reboot the system you hit the CTRL-ALT-DELETE targets and the score resets to 0000 and the score wheel increments 1.

How the head unit is built. It has two doors. open the back one to move the score wheels out of the way and the other doors allows access to the LED displays.

Justa close up of the displays. That LED display is not functional.

Installing the pop bumpers.

Shooter lane. You can see the skill shot near the top.

Drop targets. One feature I really like about pinball machines are drop targets so I have lots.

This is what the pinball machine currently looks like. You can see the LED dot matrix display on the head unit. its resolution is 16×72. It will most likely be multiplexed and controlled via shift registers.

Mode Ideas

  • Kid Hacker Mode: All 12 year old kids can hack computers in an instant. When in this mode it will randomly pick a “kid hacker” from a movie.
  • Jurassic Park: In the first movie the young girl hacks a Unix graphical interface to lock down the compound.
  • HAL 2001: Knock down the drop targets to do what Dave does in the movie. As you progress in the mode HAL speaks slower.
  • USSR Mode: Upon entering this mode the machine will randomly freeze up. You fix it you have to “tilt” the table simulating smacking a computer to get it working again. This happens 9 times. If you keep your ball alive during it you get a big bonus. Keeps track with a nixie tube.
  • Hacking Mode:This is multistage and is the default mode.
  • Dial-in: First you have to establish a connection. Hit targets around the play field to connect. sounds will be like a 56K modem.
  • Connect to router: You need a password. Targets turn into password inputs. Will enter generic passwords like “PASSWORD”, “1234”, “PACKER04”.
  • Once connected it will randomly pick which mode you can do. Themes range from the WOPR terminal in Wargames to stopping Skynet.
  • Independence day: Upload a virus to the Aliens before the world is blown up.
  • Mission Impossible mode: A floppy disk acts as a barrier and only inserts into the floppy drive when in this mode. Copy all the files (hitting all targets) before the time runs out.
  • Golden Eye: I’M INVINCIBLE! is what is said when you lose all your balls.
  • Rick Roll is going to happen somewhere.
  • Hello World shall make an appearance.
  • Dot Matrix Printer parts will be used in the field.
  • Every so often you will get a “Permission Denied” on the screen. You can not score any points till the “Override” button is pressed.
  • Blue Screen of Death
  • Firewall mode: To get past the firewall you need to traverse all ramps.

This is a video dump of the pinball machine.

This is the second work log for the pinball machine. Not much has changed but there are a few ramp ideas and such.

Little demo of the flippers and various shots around the playfield. Next video should have working I/O so the slingshots will work.

Here is a little test of one of the 4-digit 7-segment LED displays. This is just a prototype and does not have the 16-segment alphanumeric units on.

The PCB for the solenoid controller is almost complete. Just need to wrap up the Watch Dog circuit. A Watch Dog just makes sure that the solenoid controller doesn’t lock up in case of a CPU lock up (i.e. crash). I am going to try a timer (kinda like a 555 timer) to the Reset Pin of the 74HC595 and the input of the timer to CLK signal. If the CLK signal doesn’t change for 1 second the 74HC595s will reset.

PCB done. I decided to use a 555 timer as the watch dog. Keeps part count low and reliability high. I will post some more technical details later.

PCB done for the input. It pulls all the inputs high and when the ball activates a switch the pin on the 74HC165 gets pulled low. The 74HC165 is a parallel in serial out which is the reverse of a 74HC595 essentially. This PCB has 32-bits worth of inputs and can be cascaded to allow more bits on the same DATA line.

Finished designing the PCB for the 4-digit displays for the Reset Vector pinball machine.

Along with the 4 7-segment LED displays it also has 2 16-segment LED displays to show which player belongs to that score.

Left to be designed PCB wise is a 16 x 72 LED matrix board, a 7-digit 16-segment display, and a RGB LED driver board.

I had some issues with my 74HC595’s. They seemed to “reset” periodically. Figured out the real problem while working on my displays. Fixed it with software.

My old routine

Latch Low
Repeat x times { Clk low , Shift bit out , Clk high }
Latch High

Seems that when that is low it can easily pick up interference from the data and clock line. To fix this I can put a pull down resistor on the Latch line but this requires me redesigning all my PCBs thus have to pay tooling costs again if I need spares or fix it in software like so.

Latch High
Repeat x times { Clk low , Shift bit out , Clk high }
Latch Low
Latch High

This way the latch hasn’t “reset” and eliminates glitches. Working fine now.

And it worked first try!

This will be a display above the row of targets in the middle of the playfield. It will display different words or numbers depending what mode the player is in.

To make sure the LED matrix setup will work I am going to get this board made. It will only cost $15 to get the test prototype PCB made compared to the $120 to get the entire matrix PCB made. With this I can test the programming and make sure the 74HC595’s and propeller are fast enough to do it all.

2 out of the 4 score displays are now working. Currently the code supports all 4 displays. Just waiting on more parts. Next video will feature the input and output boards working.

This will be a display above the row of targets in the middle of the playfield. It will display different words or numbers depending what mode the player is in.

To make sure the LED matrix setup will work I am going to get this board made. It will only cost $15 to get the test prototype PCB made compared to the $120 to get the entire matrix PCB made. With this I can test the programming and make sure the 74HC595’s and propeller are fast enough to do it all.

The 32-bit input driver and the 32-bit solenoid driver.

Finalized side art.

Some specs of the display:

  • 16×96 resolution, single color (red)
  • LEDs run at 1/8 duty cycle due to updating the display 2 lines at a time. Line[n] and line[n+8] get updated at the same time.
  • Row selectable for the fastest update speed.
  • Estimated refresh rate of 100Hz. It is written in spin so the driver is fairly slow but this is mainly limited to the speed you can clock into the 74HC595s that do the row and column addressing.
  • With all LED’s lit it will draw roughly 1.5Amps.

Received my JWS480P-48 power supply. It provides the 48V needed for the flipper coils. At 10A of continuous current it has plenty of power to cope with it. It also does 20A peak for awhile which is enough to power a couple pinball machines at once!

Got a lot of work done on Reset Vector. I/O is working along with sound. The game currently supports 4 players. Need to finish the playfield layout and get the dot matrix display running.

Atari A/V Mods

You’re not getting old. Thats RF fuzz! – SOLD OUT – NOW OPEN SOURCE

I used to offer a variety of A/V mods choices for the Atari 2600 and Atari 7800 consoles. The modification adds a S-video and composite video output to the Atari along with Stereo sound. The mods where very easy to install. If you can solder a wire you could install these kits.

Comparison between stock RF and the mod on a 7800.

Different Modding Options.

The install guides to the mods can be found here.
All FreePCB Files can be found here.


Ben Heckendorn’s Video Review of the 2600 mod: Link
Garner’s Video Review of the 2600 mod: Link
Chris Kennedy’s Review of the 2600 mod: Link

Atari 2600 Video Mod V2.2D PCB

Atari 2600 P V1 – Design Phase

Ahh the Atari 2600. Beautiful, majestic, and erm ancient? Codenamed “Stella”, it was one of the first home consoles to feature a CPU. This enabled the 2600 to basically do anything the game programmer wanted it to do. Also, It was one of the first to feature a cartridge based system for games.

As always heres a sketch of the Atarip design I drew up.

I decided to get a little fancy this time and do all the designing in Lightwave instead of using Sketch-up. Surprisingly It took roughly the same time to finish the design. Also, Lightwave’s wireframe rendering looks much more professional than Sketch-up’s.

This time around I decided to use a 3″ LCD instead of the usual 5″ PSone screen because it enabled me to shrink the size of the portable to about half of what my NESp is. The 8 AA batteries should give it a decent battery life to. There is going to be a built in paddle controller on the left side as well.

I tried to make this portable look as much like the original Atari 2600 as possible. Wood Grain and brushed-chrome switches are a key features to this design.

Drew up this Adobe Illustrator Layout of the case design for the Atari. The gird is set in 1/8″ increments so it is easier to hand make. Plus I can print the design out in real size and test out the control layout before cutting. There is a slight design change from the Lightwave renders and the Layout. I added another switch so I can have the reset switch identical to the select switch.

Updated the render of the case to include the extra switch. To be honest, I am kinda liking the crazy layout of this portable. Starting to look more like an old time radio of something along those lines. I also redid the wood textures like I did with the NESp V2.

Here is a view of the portable like it you where actually playing it. The Cart does not get in the way and even acts like a sun visor keeping the glare off your screen (cough* design feature).