bcombee

I finally got my SDrive Nuxx built up and working today... I ended up having to do a bit of circuit debugging that I wanted to document here. I was using c0nsumer's circuit board, and I'd order all of my parts from Digikey and Newark. First problem: when installing the SD card holder, the pins on the side are important for detecting the card and for detecting the read-only switch. I didn't realize this and installed them with too much solder, causing a bridge. I had to remove the R/W switch in order to get access to the pads to rework this, and even now, my board doesn't detect card removal because I wasn't able to find the last bridge that's tying the card detect pin to the SD card shield. Second problem: be sure to double check that all your components are soldered and that your IC is in the right way. When I first tested the board, I'd installed the ATMega8 chip backwards AND I'd left the socket unsoldered. Oops. Fortunately, there was no damage to the chip. Third problem: the sideways switchs are a bit fragile. I busted my "Right" switch while working on the board. Fourth and most major problem: be careful with installing the right size capacitor. I kept trying the board and not seeing any of the LEDs light. I spent a lot of time trying to verify that the ATMega8 chip was OK and was programmed right, and in the end the problem was that I'd installed 22nF caps with the crystal instead of 22uF. This meant that the crystal didn't oscillate, which meant no clock for the circuit. It's working now, and I should soon get a SIO connector so I can stop using the makeshift SIO cable I'd setup from the remnants of my XM301. It's a very nice setup, and c0nsumer was quite helpful with debugging things. I ended up doing quite a bit more work than needed, including writing a test program for the board using an Arduino board as my programmer. I've got an idea or two for other 8-bit hardware projects, and we'll see if I end up developing them. I've also not given up on the idea of a SDrive that would fit in the XM301 enclosure, but I'm not completely sure how to handle all of the controls and indicator lights for that one.

I think the circles just indicate that there's an intersection. Where lines cross and there's no circle, that's supposed to mean no intersection. I've seen that kind of notation used before in schematics of simple ROM chips. It looks like they're used here as a simple ROM to select other components based on the data lines.

I got my PC board, chip, and panel set in today. I've got half-a-dozen kits waiting to be assembled right now, but I hope to get to it soon. The only thing I'm varying from the standard form is that I've got a SIO cable scavenged from a XM301 modem, so I'm planning on soldering that directly to the DB15 holes. If I get a spare SIO connector in the future, I can replace it then.

This is fascinating. The difference between this and the common CX85 is the order of the numbers. The CX85 has them in standard calculator order with "123" at the bottom, where this has them like a telephone keypad with "123" at the top. This is almost certainly a bit of prototype hardware, as I can't find any references to it being released. Atari may have tested this and found that it was the wrong layout to bundle with their Bookkeeper application, leading to a reordering of the keys and a bump in the version number. I expect this has a similar circuit to the CX85, although some lines may be wired differently. The CX85 uses a 74C923 keypad encoder chip which reads the 17 keys in a 4x5 matrix and outputs what key is hit using 6 output lines -- one line indicates that there is a key down and the other five encode its position in binary. The keypad could have supported an extra three keys without any big changes. The joystick trigger input is used for the "there's a key" signal, and the four directions and one of the paddle input lines are used to identify the key. I expect that the CX84 may have been wired to use POT A instead of POT B, and Atari changed the schematic slightly when they changed the layout. You definitely need to document this find, it's very cool.

Hey, I don't know if you've got your PCB house lined up yet, but I recently found out about the Propaganda service that Seeed Studios is doing for open source hardware projects -- $30 gets you five boards as long as your designs are released in an open-source compatible license like Creative Commons SA. I'm going to use it for an Arduino shield I'm working on. I've ordered a few products from them and I like their service. Details on this deal are at http://www.seeedstudio.com/depot/propagand...orks-p-111.html.

Ah, that's "This Planet Sucks", a really nice and hard homebrew. More details at http://www.atariage.com/store/index.php?ma...products_id=197 -- I've got one of the pre-AtariAge copies that I got at a CGExpo.

The last game is Chopper Command, just a rather extreme closeup. I was wanting to show the color in the skyline. The camera probably made it worse than it looks on the set. It's a 40" 1080p LCD TV, and the input was using film mode. Thanks for the broken pin fix idea. If I have problems and need to resolder it, I'll try that out.

No, they're s-video only. I used a composite cable for testing, but I didn't have it hooked up at all when taking the screen shots. However, I did have my set in film mode and it was mid-day with a lot of extra light.

I'd also add a quick guide to soldering to pins. I've done a lot of through-hole soldering and some surface mount, but getting a good bond to a chip pin requires a few different techniques. What worked best for me was to tin the wire with extra solder, then hold the wire to the pin and apply heat to wire while pressing it against the pin. I had some problems initially with the stranded wire getting frayed when I was trying to work like I normally solder, where I apply solder to the joint after it's had a moment to heat. I'd also include tips on using a multimeter to check for continuity to make sure there's no solder bridges between the pins. I ended up with one that I found before powering up my device that I was able to fix, but if I'd not done the check, I might have messed up the circuit.

Do you feel like the current 1.0 schematic is accurate for the purposes of ordering parts? I need to make an order with Digikey for other projects, and would like to add these to the order so I'll be ready when you get production parts.

Here's the console Here are close-ups of the jacks Here are some screen shots: The only oddness I've noticed is that the TV's video processor doesn't love double line kernels and will offset the second scanline some. However, the picture is still far nicer than I've ever seen a 2600 do. The colors look more subdued here; I'm not sure why, but it's likely just my screen's adjustment, since I like to have more of a film-like look. It may also be a weak joint with the color pin on the TIA, but I'd expect that to be more intermittent. I'd show the interior, but I'm not planning on opening this one up until I move the mod to another console.

OK, a few more minutes of fiddling, and I think I've got an OK joint for now. However, I'm going to try to find my 4-switch or 6-switch and move the mod to there. No only does it have more room inside, it really would look nicer too to have all the ports on the back. However, I still get video out after putting the case back on, so I'm counting this a success.

Success! Then failure. I got everything soldered onto Junior #2. While opened up, I verified that S-Video and sound were working, and the picture looked quite nice. Then, while trying to get the board positioned, pin 9 of the TIA which I'd desoldered and lifted broke off the package, leaving me just a little thin strip of metal to try to connect. Grrr! The wires going to the TIA are pretty stiff. One thing that helped -- I opened the images from Longhorn's guide up in their own pages and used Firefox's zoom to make them larger. The default size on the guide page is a little small for me to easily follow. I'm going to try to get it reconnected, but so far my attempts have come loose almost immediately, so I may have to try some alternative method, like adding a second wire and then soldering to that. If I can't get this going, I guess I'll have to try console #3

It's actually on the Longhorn PC board pretty well -- it was the contact with tops of the other ICs that was problematic. I ended up scavenging some parts from the 2600 board for other projects; you never know when switches, DB9 connectors, and a 2600 cart connector will be useful. Maybe I'll finally do a Flashback 2 conversion. I'm going to pull another Junior from my storage room tonight and try it out.

OK, I got the mod installed in my 2600 Jr, but I get no video. I suspect that a lead came off the TIA. Lifting the leads wasn't too bad, but I had some difficulty soldering the wires to the chip and probably need to redo those connections. Getting everything to fit inside the case was also a bit tough, snd the sticky tape just doesn't work to hold the board in place while you're working. I verified that there were no bridges and that I had continuity from the TIA pins to the 4050. I also read 5V between the buffer's VCC and GND pins. At this time, I think I may have pulled a bad 2600 Jr... I made the mistake of not testing the console first. The main reason I suspect this is that the sound also wasn't working, and that's a totally different part of the circuit. Fortunately, I've got a few more Juniors, so I can pull a motherboard from one of them and reuse the case I already drilled. I'll be sure to verify the console works first before I start opening it up and soldering.

I got my kit in the mail today and it's already soldered up waiting to be installed one of my 2600s tonight. For the most part it was a smooth assembly. The surface mount chip wasn't too hard to get into place. I did find the two .1uf caps next to that chip to be a little problematic -- they were wider than the space on the board, and I'm afraid of a short between the legs. The resistors weren't too bad; I first installed all the 75ohms, then used a multimeter to get the values of the rest and stuffed them in the board. I really like that you have the resistor values silk-screened instead of R numbers; it was much easier to match things up. The only other footprint issue was the 7804; it took some delicate work to avoid solder bridges.

So, looking at the SCRAM manual, they just say the 16K version takes longer to load. After you load the initial loader using CLOAD, the 16K version pulls the rest of itself into memory in two parts. If it's loading BASIC code that then used DATA statements to load machine language, that would explain how a second load would reduce the memory usage.

The Atari 800 originally shipped with a single 8K memory module, so adding a 16K module to get to 24K wouldn't be too unusual.

Thanks. I like my projects to look as Atari as possible. Can you send me the PCB files when you get it done? Yeah, I'd follow NUXX's lead and have all the design files in the open. I may end up using ExpressPCB -- they do three boards for $51+shipping and the size is pretty close to perfect for the project. What PCB house are you using?

Hmmm... I actually like the XM301 case idea. I've got a spare one here that's waiting to be Dremmeled. Advantages: 1) you can get XM301's new for $15 from B&C, so the case is much less expensive that a new enclosure and panels. 2) they come with a SIO cable with a strain relief clip; just cut it from the PC board them solder it to the SDrive PCB. No need to destroy a cable or use a DB15 adapter. 3) there is a slot up front that will let a power LED shine through. It's got red plastic on it, but you probably could still see different colors if you used a bicolor LED to indicate R/W. 4) genuine Atari look and feel The case is setup to handle a 122mm x 62mm PCB with notches in the back and two support holes. I just traced my own PCB and measured the dimensions. The telephone port on the back is large enough to support a MicroSD slot, but that's a pain to work with as it's surface-mount with the contacts under the shield! That means having to do reflow for that one. However, there's room on the back for mounting buttons and a real SD slot, you just want to be careful to avoid cutting away too much plastic. I'll probably go ahead and build one from the NUXX PCB to try out the device. Then, I'll make my own PCB and try that too. Then, it looks like I could probably sell my original one, as there's a market for prebuilt units This sounds like a fun way for me to get into PCB layout too. The freeware version of Eagle CAD can only do 100mm x 80mm boards, but I figure one that size will fit OK in the XM301 case, it just won't reach to both sides.

At $40 per panel, I'd probably be more interested in just going without or doing one myself using plastic with a local laser cutter. Does the Front Panel Express software export in any formats that can be reused by other programs?

I was wondering about the cost of the Front Panel Express pieces. I looked on their site, and those seemed fairly expensive. Are there discounts for multiple panels; if so, would you consider bundling those with your PCB?

I'm very interested. I just read through the SDrive documentation, and it looks like a very nice project. It also seems like it would be doable as a shield for an Arduino board, although there might be problems with the clock rate being different, since it uses a 16MHz oscillator instead of the 14.31818 MHz one in the SDrive schematic. I assume that was picked to sync up with the clock rate used by the Atari, but I've not read the source yet to see.

What about a complete kit, but with the buyer having to solder up the PC board himself?

You can get a listing from Digital Press by going to their search page at http://www.digitpress.com/DP/cmf/search.cmf and only picking the "Atari XE" system choice, then hitting "Find It".