Posted: Sun Jul 03, 2011 11:40 am
This is my solution I posted this a while back, it makes programming easy. Alternatively you can use a single gate, a 1-bit MUX for either polarity or a '157 if you have multiple clock sources.
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I didn't really intend for it to be used for sound. Since how the FC carts don't have any extra pins hanging around and most games don't use the sound pins I figured a developer may want to use the sound pins for other features like mapper disable which would seem highly desirable for someone developing on UNROM or whatnot. We could connect them to ADC into the AVR and that wouldn't take a pin since how we weren't using that one anyways. You're the only one that was asking for FC connector though Memblers, so I'll most likely do it how you see best. One free option could be to provide solder jumper for selection of analog or digital input to the MCU.Memblers wrote: I'm not sure why the MCU would connect to the audio pins, it seems like only an ADC and/or DAC would be usable.
I think we're all agreed to make EXP0 mapper disable, and since I see this as a common "multiuse" pin I think it would be good to give it one of the 3 pins we have left. Leaving us with 2. (This is what I also wanted to assign to FC "audio in" pin 45)Memblers wrote:Regarding the expansion pins on NES cartridges, that normally aren't used. It's time to use them, here is what I'm proposing:
Originally I thought I would use EXP7 for audio in (from the NES), it'd be nice to have but I'm not sure it's needed. So I put another ground there, to give the CAN bus some help (and maybe hope for higher speeds).Code: Select all
EXP0: in - CopyNES mapper disable EXP1: I/O - CAN bus H EXP2: out - A0 (PRG) EXP3: out - A1 EXP4: out - A2 EXP5: out - /CE for parallel port device EXP6: out - audio out EXP7: Ground EXP8: I/O - CAN bus L EXP9: out - PRG R/W
This standard would apply to both expansion port devices, and NES cartridges (and requires both to work, of course). So I'm curious if anyone has any thoughts on it, or other alternatives.
Problem is that they are always used. When there's not a sound expansion, the audio in and out pins are shorted together to pass the audio through.I didn't really intend for it to be used for sound. Since how the FC carts don't have any extra pins hanging around and most games don't use the sound pins I figured a developer may want to use the sound pins for other features like mapper disable which would seem highly desirable for someone developing on UNROM or whatnot.
Right, there are a lot of outputs from the cart. You probably know that the data bus is shared with the exp port, so when the cart is in the NES there is plenty of I/O since this standard provides the /CE and even some address lines. Other than the mapper disable, I just can't imagine what kind of input a cart could possibly use though, when it's outside the NES. Maybe in-circuit programming for an MCU or CPLD, but stuff like that I believe is better served by adding a dedicated connector to the cart and leaving the EXP pins free. Such as the programming voltage you mentioned, it makes more sense (IMHO) to have it on another connector instead of through the EXP connector. Mostly since it's all more of a one-time use thing (when initially building the cart) that is pretty boring for normal users. But programming voltages are a thing of the past, that would have been more useful 20 years ago instead of today, heheh. In fact, I believe there were some Atari 2600 carts (I wouldn't call them dev carts, more like homemade OTP bootlegs) where the cart does plug into a stand-alone programmer to burn an onboard ROM.While I can see why it would be OUT for use in a console, I can't see why they would be anything but IN for a dev cart.
Yeah I agree with what you're saying here. I didn't really see a large use for the EXP pins aside from mapper disable. But I figured if there was board space why not atleast provide the pads on the board for someone to make use out of the EXP pins.Memblers wrote:
Problem is that they are always used. When there's not a sound expansion, the audio in and out pins are shorted together to pass the audio through.
But yeah, if there's an ADC pin free, then connecting the audio out couldn't hurt anything. Anyways, if I make an FC dev board, the mapper registers aren't going to overlap memory, so nothing special will be needed.
No big deal what happens with the exp pins on this interface really I suppose, sounds safe enough with the tri-state buffer. If there are some I/Os from the MCU left over, I'd hook them up to some status LEDs or something. Everyone can appreciate some blinkenlights.
I'm onboard with the multiple standards. Maybe the best answer is to only standardize the pins already used with copyNES, powerpak, and sound.Main reason I'm so concerned over the EXP port, is that no one else has yet to use it for anything (other than CopyNES in rare cases, and PowerPak sound more commonly, and that dumb unreleased gambling modem thing). The cheap dev cart I'm making will use them however, I just want to make sure if people want to use it with an interface like this I don't have to give them special firmware to do it, or tell them to move jumpers around, etc, sorta defeats the convenience of it all. I don't think people would be too thrilled if the first real use of the expansion port includes multiple standards :/
Yes exactly it's an active low signal. Now I'm not sure it it's always the inverse of CHR A13, because I don't know enough about where those signals are coming from. But the Kazzo gave CHR /A13 a separate signal from A13. Presumably because it uses A13 for the PRG memory also, so for the Kazzo atleast CHR /A13 is not always the inverse of A13 because it's basically CHR /CE.qbradq wrote:
I am confused on the CHR /A13 bit. Shouldn't this be high when accessing CHR-ROM? This should always be the inverse of CHR A13.
Thanks for backup yes I am only working on Famicom. By the way my name is Farid not FarridSkinnyV wrote:I would be interested in having the space to solder a famicom connector. I always end up with pirate FC cart that I would be happy to have some way of connecting to the dumper without the use of an adapter. If you can find the space I think it would be useful for some. Look at Farrid, he almost only deal with FC cart, so i'm sure some people would use it.