Building a Hydra system from the book. Need to confirm a few things.

RobotWorkshop

I had built most of a Parallax Demo board on a hand wired prototype board and am now going to convert it to a Hydra. I've purchased the SD Max storage card for the Hydra as well as the Hydra book. After going over the book I have a couple questions about the hardware and want to confirm them before I finish wiring it all up.

- For the game pad indicator resistors R32, R33 as 1-2.2K in value. What is the real value that is used on the production Hydra?

- Another resistor R31 is listed as 10-22K. I'd also like to get the value used on the Hydra for this one.

- In regards to the EEPROM on the Hydra itself is the 10K pull up really wired to the RESET line as shown in the book or should that really be 3.3v?

- The signal names for the VGA don't match up between pages 117 and 161. I think I can tell what they are supposed to be but would like to confirm them too.

At the moment these are the only questions I had on it. If anyone knows the answers that would be great! I've got some spare time this weekend and hope to have it all re-wired and working.

Robert

Post Edited (RobotWorkshop) : 4/11/2008 8:39:47 PM GMT

RobotWorkshop

One other question I have is in regards to the 74HC244 used to buffer the VGA signals. One 74HC244 should do the job. From the book it suggests that it may be using a pair of these chips and only half of each. Is that correct? If so why?

Robert

kuroneko

RobotWorkshop said...
- For the game pad indicator resistors R32, R33 as 1-2.2K in value. What is the real value that is used on the production Hydra?

- Another resistor R31 is listed as 10-22K. I'd also like to get the value used on the Hydra for this one.

- In regards to the EEPROM on the Hydra itself is the 10K pull up really wired to the RESET line as shown in the book or should that really be 3.3v?

- The signal names for the VGA don't match up between pages 117 and 161. I think I can tell what they are supposed to be but would like to confirm them too.

- One other question I have is in regards to the 74HC244 used to buffer the VGA signals. One 74HC244 should do the job. From the book it suggests that it may be using a pair of these chips and only half of each. Is that correct? If so why?

1. 1K [noparse][[/noparse] 1 ]
2. 10K [noparse][[/noparse] 1 ]
3. Can't really say, the demo board seems to use a pull-up. Probably best to ask Andre' about this design decision.
4. Well spotted, p.161 doesn't make much sense (how much blue do you need), the suffix is correct. I'd use p.171 for reference.
5. The 244 has 2x4bit buffers (marked A and , it's still the same chip.

[noparse][[/noparse] 1 ] measured on my Hydra board

OwenS

[noparse][[/noparse]quote]
- In regards to the EEPROM on the Hydra itself is the 10K pull up really wired to the RESET line as shown in the book or should that really be 3.3v?

If I remember correctly, a while ago someone noticed that this caused issues with some Hydras. The connection is wired to the RESET line, but it would be better wired to the 3.3v line (As it is, it is possible to accidentally reset the Propeller when using the I²C bus, if I remember that post correctly)

RobotWorkshop

I have the most of the Hydra assembled now and should be able to test it out this afternoon. I think for the moment i'm going to leave the pull-up going to 3.3v and can change it later if needed.

If anyone knows the reason to connect it to the RESET line instead and it should be there then please let me know and i'll make the appropriate change on my board.

At the moment the only differences on my hand wired version is:

- EEPROM line tied to 3.3v instead of reset line
- Left off the gamepad inserted LEDs
- 8 extra LED's wired in parallel with VGA signals on output out 74hc244 (these are left over from when it was a demo board so I kept them)
- DAC Resistors on VGA connector are the values like the demo board instead of the Hydra (should be ok)

Since the gamepad connectors don't seem to be available I found an NES Four Score adapter on ebay. I'm going to cut the end off that and hook it up to my board. With that it should be a full Hydra!

Robert

AndreL

That original design element was recommended by chip gracey when I initially did the design, for reasons relating to the reset, and brown out. Just put it thru the pull up and 3.3v.

Andre'

RobotWorkshop

Hello Andre'

Thanks for the clarification! I've got some of it up and running now. The system comes up and I can use the game pads to play some of the games with my son. Sound works fine too. I'm having a problem with the keyboard and mouse but it may be an issue with my wiring. It's nice to finally be able to start going through the book in more detail now.

I've noticed that the games sometimes come up in black/white even though it is a color game. I'm using a 560 ohm resistor for the broadcast mode (like the demo board) instead of the 470 ohm like the Hydra. Would that cause this sort of issue?

Robert

RobotWorkshop

I fixed the Keyboard/mouse issue. It was a silly mistake. The emitter and collector on the 2n3904's were swapped. I guess that can happen when it's near 2am when installing them...

The only remaining issue is the one regarding the lack of color in some programs which should have it. I'm going to try another monitor to see if that helps.

In the meantime we're having fun playing some of the games that came on the SD Max storage card for the Hydra. I'm really pleased with that optional card and it was nice to have some of the games pre-loaded on it.

Are there any programs that require the 512K SRAM card yet? I may have to pickup one of those.

Robert

AndreL

There are a couple demos/games that use the SRAM card, it will interesting to see if it works on your board since its VERY fast. And the color issue, like others have noted is just xtal variance, make sure you have the right kind of crystal the is oscillating in parallel mode, not serial. And you have to fudge the frequency +- 2-5Khz if you have an iffy xtal. Otherwise, 99% of all the demos work as is with the xtals that we manufacture the Hydra with.

Andre'

RobotWorkshop

Hello Andre'

I've got some 10Mhz crystals on order and i'll see how they work. They are cheap so I got a few different styles and manufacturers so I hope to find one that makes it better. I think it's close now and by changing the crystal I can get it right on.

Your book has been an excellent resource and I had bought it early on before I thought I would want the whole Hydra. It's been fun to build and only took a couple evenings to convert my hand wired demo board to make it a Hydra clone. Even though some prototypes can be a bit unwieldy I am pretty particular about keeping all my wiring neat and tidy, using the bypass caps, and do whatever I can to ensure it works reliably. I don't expect any issues with the SRAM card but it is something to watch out for I suppose.

Since the connectors for the gamepads are nowhere to be found I had picked up an NES FOUR SCORE adapter and just chopped off the end to wire it up to my board. I was a bit concerned if that would work at 3.3V instead of 5V and through I may have to hack that board to make it work. Luckily it didn't seem to be a problem and it works just fine at 3.3V. It makes a great solution for anyone that wants to build their own board and wants a nice way to connect the gamepads!

For the cartridge connector I just bought a 20-pin edge card connector w/mounting ears. This is on a pair of metal standoff's with a short ribbon cable going down to the board. I kept the wiring as short as possible to avoid any noise issues. So far so good.

The only mistake I made was installing the four 2n3904 transistors. It was late and I knew I should go to sleep but figured I would do just a little more. Well I guess I should have had another cup of coffee because I had reversed the E and C on them. Didn't damage anything but the keyboard and mouse didn't work. I just turned them around in the morning and that fixed it.

Robert

AndreL

Sounds good, yup, there is no way to tell EBC on a transistor, its supposed to be EBC, left to right on the flat side, but that's not necessarily true, I have seen two manufacturers label them EBC, CBE from the flat side, so not only do you have to be careful, you have to make sure you look at the manufactures docs!

And on the NES connectors, yup, you have to cannibalize them, no one sells them to the public.

Andre'

RobotWorkshop

Swapping the crystal got the color working! On the Toshiba set all the color programs work perfectly. I now get color on most programs when plugged into the Sony set as well. Things are good now....

Robert