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Any chance of seeing an SX48 con carne??? — Parallax Forums

Any chance of seeing an SX48 con carne???

cbmeekscbmeeks Posts: 634
edited 2005-12-12 15:50 in General Discussion
Anytime soon?

I have the protoboard and it is great. However, I am finding that when I need to run a lot of lines (for parallel memory lines) I have literally dozens of 8" wires when if it were on a breadboard, that could be shortened to 2".

Just a thought. smile.gif

cbmeeks

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Comments

  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2005-12-11 16:00
    Personally I don't like the 40 pin DIP interface.
    I have a BS 40p and it is hard to plug-in and remove.
    If I try to unplug it, I really feel that great care is needed to avoid damage or bent pins.

    Why not get rid of all the individual wires?

    What I have done to the SX-52 protoboard is to build a ribbon cable adapter that alternates signals and ground lines [noparse][[/noparse]to eliminate cross-talk].
    I can use 34pin ribbon cables to get two sides. and a smaller 16pin ribbon cable to the other.

    The two ports closest to the center of the board are the most problematic as the cable may interfer with the reset button and be subject to heat from the microprocessor.

    Also, I have made a prototype SX-28 board that runs 16 lines into a 34 wire ribbon cable with the RTCC and the RESET included.
    The other·4 lines are interfaced via another ribbon cable that plugs into a DIP socket. The first 4 Port B lines are available both at the 34pin header and the DIP plug.· I can easily split that into two 8 wire cables and use one for serial with hardware handshaking while the other can have the comparator in use eslewhere.

    As you can see, I strongly prefer the ribbon cable to a 40pin DIP kind of setup.
    It is easy to plug and unplug. Also, you don't have the problem of inflexible connections between two devices [noparse][[/noparse]which may cause failure].

    I will try to get some photos to post.

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    ······································································ Warm regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan

    Post Edited (Kramer) : 12/12/2005 3:53:03 PM GMT
  • Mike CookMike Cook Posts: 829
    edited 2005-12-11 16:55
    Personally I just use the SX52 con carne and ignore the upper nibble on port A. But at almost $60 each, I would strongly consider doing a one off board with www.expresspcb.com 's mini board service.

    Sorry I'm CHEAP!

    Mike

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  • Ken GraceyKen Gracey Posts: 7,401
    edited 2005-12-11 16:59
    Hi cbmeeks,

    Unfortunately, no. The SX48 Proto Board is our primary solution. The SX52 Con Carne never sold very well, mostly due to the cost. But the proto boards - they're another story. Use them if you can. There are at least five to six variations customers would like to have on SX48/52 boards, which is why we designed the Proto Boards and sought their input in the early design phase. To keep everything inexpensive, we need a small number of solutions with a reasonably high volume. This way we can serve a hobbyist as well as a volume consumer.

    And that's a tough message for me to write, considering I'm a "yes" kind of guy.

    Ken Gracey
    Parallax, Inc.
  • Mike CookMike Cook Posts: 829
    edited 2005-12-11 17:19

    Hi cbmeeks,

    If you use expressPCB, BTY there is a part for the SX48 listed in the forms:

    http://forums.parallax.com/showthread.php?p=560489

    You could do the following:

    Their mini board service is for 3 2.5" x 3.8" boards. If you could lay out 4 carrier boards on each panel then you would have a total of 12 carrier boards for about $61.00. Now you need SX48 chips, some headers and socket, for the resonator, if you add it on the carrier. So figure another $75 or so for SX48's and headers/sockets. Now your up to about $136, about 11.34 each plus your time.

    Don't need 12 of these things? Sell the excess on ebay for $25.00 each, I'd buy one! So 11 @ 25.00 is: $275.00. So for a little bit of your time, yours is free and you made about $139.00 for your time. Seems like a deal to me!

    Mike

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    "OEM NMEA GPS Module" Now available on ebay for only $19.99, FREE shipping until 2006!

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  • ForrestForrest Posts: 1,341
    edited 2005-12-11 17:51
    I think Ken posted the gerber files for the SX52 Con Carne board on this forum shortly after the SX48/52 Prototype boards started shipping. I tried using the search feature in this forum but couldn't find them - you might want to try searching yourself.
  • Mike CookMike Cook Posts: 829
    edited 2005-12-11 18:00
    They're here:

    http://forums.parallax.com/showthread.php?p=539600

    Mike

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  • cbmeekscbmeeks Posts: 634
    edited 2005-12-11 19:19
    Thanks guys for all the suggestions!

    And I understand what you are saying Ken. smile.gif

    But I have to admit, I didn't think of ribbon cables! Great idea.

    Kramer: I would love to see those photos.

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  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2005-12-12 08:06
    A promise is a promise. I just have to start digging things out and readying a photo shoot.
    Another busy day.

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    ······································································ Warm regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan
  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2005-12-12 12:39
    This are the photos regarding using a ribbon cable connector.

    I must say that I had a lot of trouble with the camera, so please excuse the quality.· Hopefully you can see that I have modified the connector rather than the board.· I simply soldered a buss wire to all of the pins on one side.· This can then be connected to ground on either the SX-48/52 Protoboard [noparse][[/noparse]via a yet to added jumper wire] or to the other board.· The purpose is to eliminate crosstalk. I suspect leaving them completely unconnected will not affect anything.

    The main fact is that you can easily·move 16 to 18 wires in a row to another board or breadboard.

    Included is my SX-28 board which interfaces 32 pins via a ribbon cable w/ RTCC and reset on two additional pins.· The RA port is interfaced from the 16pin dip along with an alternate route for the rb0-3.


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    "When all think alike, no one is thinking very much.' - Walter Lippmann (1889-1974)

    ······································································ Warm regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan

    Post Edited (Kramer) : 12/12/2005 12:46:40 PM GMT
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  • cbmeekscbmeeks Posts: 634
    edited 2005-12-12 13:18
    Those look really cool.

    I'm still not sure what you mean about the ground wires. I understand you need a gnd wire to help reduce crosstalk but out of the 36 pins of the SX48, how many gnd pins? Do you have a gnd pin for EACH I/O pin? Are the interleaved?

    Thanks!

    cbmeeks

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  • LoopyBytelooseLoopyByteloose Posts: 12,537
    edited 2005-12-12 15:50
    I really should be preparing for my teaching for tomorrow, but fun is fun.

    You don't ground the SX48's pins, they are all available for use. You do ground alterating pins in the ribbon cable connector, which reduces the capacity by half. {The· 2nd photo is a bit unclear, but you can see the glint of solder in the top line of pins - I ran a wire to the top 17 and soldered each pin to it.]

    In the photo, every other connector pin is connected to a common wire which may be grounded by connecting a wire to the board's Vss which has a lot of locations. If you managed to fit in all three [noparse][[/noparse]the second 34pin connector is a bit tricky as it might block the reset button and interfer with cooling the microprocessor], you would have to daisy chain them all to ground to the board at one and only one location.

    So the 34pin connector has 17 pins that are grounded and virtually unused. You could provide other signals on those pins by bending them straight. Then connecting as required. If these signals were comparatively 'slow', they would similarly dampen crosstalk. You could even provide a variety of votages if you set up the proto board as the main source of power [noparse][[/noparse]I suspect you would want to add another regulator or several].

    Here is the rationale.
    It really is inconvienent to go from a Single-in-Line format to the ribbon cable format [noparse][[/noparse]which alterates]. But ribbon cables really eliminate a lot of messy wiring. When you get to the breadboard at the other end, you want to preserve the single in line format again. So basically you must use merely half the wire and cross talk prevention is a justification for the waste.

    So, Grounding is just an additional cross-talk prevention.

    There are a number of ways to do this with ribbon cables and some of the others may work just as well and require less costly connectors.
    The only oddity that comes into play is that larger ribbon cable plugs don't come in multiples of 8. If you look carefully at the 34 pin in the·third photo, you may notce that the two extra pins are bent to the left side so that I could use them to either provide Vdd, Reset or RTCC in any combination.

    Optionally, you may just remove them as redundant. They become a crowding issue if not really needed and may cause shorts.

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    "When all think alike, no one is thinking very much.' - Walter Lippmann (1889-1974)

    ······································································ Warm regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan

    Post Edited (Kramer) : 12/12/2005 4:09:06 PM GMT
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