nesdev.org

I'll be submitting an order later this week to the PCB fab for ~100 EXP boards. I received a few good suggestions last week regarding the EXP layout. I revised the board based on these...

Move 3.3v VREG and CPLD to CPU board.
This will free up space for additional headers and consolidate all the components on the CPU board.

Add 16-pin IDC header that is Famicom EXP compatible.
Using an IDC16(F)/DSUB15(M) cable, you can plug in Famicom EXP peripherals such as the Famicom keyboard.

Add a 4.7K through hole resistor between EXP port pins 3 (Audio In) & 9 (Cart-EXP6).
This way you can play Powerpak/MMC5 games with extra audio output without doing a hardware mod. I also added one for the Famicom EXP port header since it has an audio in.

Here is pic of the board in FreePCB...



All EXP port signals are available through one of the headers (some are on multiple headers).

J1 - EXP 48-pin Connector

J2 - Famicom EXP Pin Compatible Header (16-pin R/A IDC)

J3 - ENIO CPU Board Header (26-pin R/A IDC)
1 -> 5V
2 -> GND
3 -> A15
4 -> $4016.b2
5 -> $4016.b1
6 -> $4016.b0
7 -> EXP9
8 -> EXP8
9 -> EXP7
10 -> EXP5
11 -> Joy2Strobe
12 -> Joy2D0
13 -> Joy2D1
14 -> Joy2D2
15 -> Joy2D3
16 -> Joy2D4
17 -> PRG D0
18 -> PRG D1
19 -> PRG D2
20 -> PRG D3
21 -> PRG D4
22 -> PRG D5
23 -> PRG D6
24 -> PRG D7
25 -> Unregulated VDD
26 -> (N/C)

J4 - Misc Signal Header (16-pin unpopulated)
1 -> 5v
2 -> GND
3 -> EXP0
4 -> NMI
5 -> EXP2
6 -> EXP1
7 -> EXP4
8 -> EXP3
9 -> Joy1D4
10 -> Joy1Strobe
11 -> Joy1D2
12 -> Joy1D3
13 -> Joy1D0
14 -> Joy1D1
15 -> 4MHz CIC
16 -> IRQ

J5 - Audio and Video Out (3-pin unpopulated)
1 -> GND
2 -> Audio Out
3 -> Video Out

If anyone can think of any other minor improvements, please let me know ASAP. Thanks!

Now I do kinda wonder if a separate power connector would be better - or at least using multiple wires per connector for power and ground. If the max current rating of an IDC cable is 1A, I think the 5V line could exceed that, and I'm sure the unregulated line could exceed that. Through shorts, faults, or even regular use if someone wanted to make such a power-hungry add-on. Might want wider traces for power and ground as well, to be on the safe side.

Having multiple connectors of the same type (the 16 pin one) seems to be an open invitation for users to hook things up the wrong way.

Why 'unpopulated' connectors? Most end-users don't have soldering irons, so it would be nearly impossible to convince anyone to use a device that needed those connectors.

Not having audio in to the NES available (except on the cart) is kind of a bummer, it's an option I'd considered for my synth exp board. But for that I'm leaning more towards using the audio out for the NES, and mixing that with my synth on the exp board and outputting stereo sound (which needs it's own audio cabling from my board, of course).

Memblers wrote:Now I do kinda wonder if a separate power connector would be better

If you planned on powering a device >200mA solely off the 5v rail, then yes. I can definitely add a two pin header for 5v/GND. On the ENIO CPU board the 5v rail is only used for powering the USB KB (< 100mA). The current draw on the UnregVDD line is less than 200mA under load to power the PIC32 and ethernet components. The CPU board will also have a miniUSB jack so it can be powered from a common 5v cell phone charger. I added this so that it could be used with other 8-bit/16-bit systems where a console's onboard 5v regulator may be overtaxed by the additional draw from the 3.3v regulator.

Memblers wrote:Having multiple connectors of the same type (the 16 pin one) seems to be an open invitation for users to hook things up the wrong way.

Why 'unpopulated' connectors? Most end-users don't have soldering irons, so it would be nearly impossible to convince anyone to use a device that needed those connectors.

The J2 & J3 headers are populated with keyed right angle IDC headers because there is very little distance between the PCB and the surface the NES is sitting on. There is not enough headroom to put in straight headers and still plug in the IDC cable. These two headers are meant for "plug 'n play" type users who want to buy a device and simply plug in a cable.

The J4 & J5 headers are meant for tinkerer types. Those who want to play around with the extra signals and don't mind soldering some wires. Also keep in mind that there is not enough overhead room to install a straight IDC header.

Memblers wrote:Not having audio in to the NES available (except on the cart) is kind of a bummer, it's an option I'd considered for my synth exp board.

I was thinking you could use the audio in pin on the Famicom EXP header for input. Are you thinking of a 3.5mm mono audio jack for input? If so, I may be able to add a footprint for one immediately above the resistors and tie the input to the Famicom EXP header audio in signal.

chykn wrote:

Memblers wrote:Now I do kinda wonder if a separate power connector would be better

If you planned on powering a device >200mA solely off the 5v rail, then yes. I can definitely add a two pin header for 5v/GND.

I had the unregulated voltage more in mind, because of a couple of optional things on my board - one is supplying the full 500mA as a USB host (may be overkill, but why not), the other is an external display that will draw about 300mA @5V. Since my board can function outside the NES also, I went with a dual 5V/3V switching regulator - so about any 9V or 12V transformer should work. Would be great to make that unneeded when it's connected to the NES.

The J2 & J3 headers are populated with keyed right angle IDC headers because there is very little distance between the PCB and the surface the NES is sitting on. There is not enough headroom to put in straight headers and still plug in the IDC cable. These two headers are meant for "plug 'n play" type users who want to buy a device and simply plug in a cable.

Makes sense, yeah there isn't much room.

I was thinking you could use the audio in pin on the Famicom EXP header for input. Are you thinking of a 3.5mm mono audio jack for input? If so, I may be able to add a footprint for one immediately above the resistors and tie the input to the Famicom EXP header audio in signal.

True, yeah I didn't think of the FC EXP header. I've wanted my synth to be compatible with that as well on a real FC, but it seems really hard to find the right kind of 15-pin connector (normal D-type connectors don't fit). 3.5mm stereo audio jack is what I would have on my synth for output, so that audio jack idea would work (if someone needed the synth audio to go through the RF modulator). Interesting idea, though not a big deal if it can't fit on the board.

I think I've found a suitable polarized power header. It's the same type used by 3-pin ATX fan cables so you could use a fan extension cable (~$2) to connect the EXP board to an accessory board.

Male right angle header for the EXP board
http://www.mouser.com/ProductDetail/TE- ... VB00MpI%3d

Female right angle header for the accessory board
http://www.mouser.com/ProductDetail/Mol ... f7J0OnQ%3d

3-pin ATX Fan Extension cable
http://www.ebay.com/itm/210mm-8-27inch- ... 2484wt_992

I've added this header (J7) to the EXP board with 15 mil traces so that it can handle at least 1A.

On the audio input, I'm afraid I can't work a 3.5mm jack into this layout due to all the headers. Jacks that are not low profile are too tall. Low profile jacks would have to be located next to one of the three channels on either side or the rear. The side channels are ruled out since the rear of the jack would overlap the EXP connector. The rear center channel could be used on another design, but there is not enough room on mine due to the positions of J2 & J3. I've put a 2-pin .100" header (J6) on the top left that connects to GND & the Audio In on the FC EXP header.

I would try to fatten up all power traces, especially grounds.

They were 12 mil (enough for 1A w/ 1oz copper) except for the 15 mil traces to J7. I've bumped them all up to 15 mil just for grins. Thanks for the input.

I was more thinking something like this (one thing I will get made in not so far future) :

http://www.fileden.com/files/2008/4/21/ ... SMSDMA.png

The EXP boards and cable components have been ordered. Should get them in by August 3rd.

That was fast. The PCBs got here before most of the components. Still waiting on the power header, 16-pin header and cable parts for the Famicom EXP connector, but here's what the board looks like installed.

Who did you order the boards from out of curiosity?

Also I saw your old youtube video from when you were working on this last year. I must say your etched PCBs are immaculate. I've tried a few method and been getting better but yours turn out AWESOME. I saw you mentioned that you use a laminating machine. Any suggestions as to what type works best, or what you use specifically? Also do you have any recommendations as to what type of glossy paper you specifically use? I found best success with laser transparencies but they are fairly expensive compared to glossy which seems to work even better for you.

I went to Gold Phoenix to get the EXP boards done. I was pretty certain I got the design right so I ordered a full panel from them. Pretty happy with the speed and quality. Since the CPU boards are much more complex, I ordered 5 of them from EZPCB. Those should be here in a little over a week.

Thanks! I spent some time trying to find a cheap but reliable method. So here's my setup...

Printer - Lexmark E260d (true 1200x1200, not 2400x600)
http://www.officedepot.com/a/products/7 ... r-Printer/

Paper - Hammermill Color Laser Gloss (cheap and almost falls off when soaked)
http://www.officedepot.com/a/products/6 ... r-Paper-8/

Laminator - Royal APL-330U (the reverse button is awesome)
http://www.amazon.com/Document-Photo-Pr ... B001B8P3TS

Paper Cutter - Some cheap-o thing from Office Max.

Drill Press - Ryobi 10" from Home Depot

Software - FreePCB & GIMP


Use your PCB software to generate at least 1200x1200 dpi images. I take the design and add at least 1/2" around all sides then cut the unetched PCB to that size. The more border the better when running through the laminator. For double sided, print the top and bottom designs on the same page (I use GIMP to combine) and fold in half around the PCB. I eyeball the board lines and tape the paper to the PCB. Put the laminator on high. Take your PCB sandwich and run it through a bunch of times (I do at least 6). Let cool for a minute then throw it in warm or hot water. After 10 minutes, slowly remove the paper and use a soft washcloth to wipe off any residue. Etch in your favorite etching solution and pop it on the drill press (if applicable). I ordered a variety of inexpensive bits from Drill Bit City.

Hope this helps!

yeah thanks for the tips and links.

Looks like EZPCB is pretty decent especially since you can get small runs with 1.2mm (0.47") board thickness. Not a big issue for your stuff here but it's pretty much a requirement for cartridge boards. They are one of the only places I've seen with decent prices for that thickness including gold plating which is key.

Didn't see much special with gold phoenix. Did they have some sort of panel deal or some other reason you choose them? Just curious, I'm always interested in finding good PCB suppliers. I've found some are better for some specific needs than others.