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mytek

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mytek last won the day on September 26

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About mytek

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    Releasing Magic Smoke
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    Santa Rosa, CA
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    Electronics, Computers, Cryogenics, Embedded System Design

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  1. Here's the difference in a nut shell... They both have the same possible features, but the XLD has all of them integrated into the motherboard, whereas the XEL needs upgrade boards to do the same. Feature XEL XLD Built-in MIDI DIN Interface NO YES Built-IN S2 MIDI Synth Socket NO YES Built-IN CF3 IDE Interface NO YES Mouse Port assignment via keyboard NO YES Disk Swap via keyboard NO YES Specific Headers for Upgrades NO YES
  2. It's very simple to interface needing only one NAND gate, and it'll let you get rid of a lot of other stuff (DRAMS, Delay Line, and misc. glue logic). 64K SRAM Circuit
  3. Tell me about it... my mind has major brain farts all the time, my fingers spell out words my mind never even thought of, and damn if I don't keep dropping caps left and right. But thank goodness for the ability to edit posts .
  4. Huh 🙃 . He hasn't even begun deliveries on the Sophia 2, what makes you think there is Sophia 3? Do you have insider information?
  5. That looks like a very good solution, and eliminates the need for the inline resistors due to the voltage level translation. Also the price is very reasonable at close to $1. Good find.
  6. Yes something like a 4.7 k would do the trick, assuming that enable was connected to FujiNet switched power.
  7. I left off motor control because I assumed (maybe incorrectly) that it wouldn't require disconnection from FujiNet. It's an open collector PNP transistor output.on the Atari side. Only chance of back feeding FujiNet would be if it were switched ON. Since nothing is actually requiring current from that output in FujiNet, a high resistance serially connected resistor would certainly suppress any back feed.
  8. I like them both, but do find myself leaning towards the XLD, simply because it packs a lot of power and also looks like something that could of come from Atari due to the reuse of the 1050 case.
  9. And check here for more specific info on the XEL and XLD, as well as a few other items: AtariBits.com
  10. Replace the 74LS08 with a SN74F08N. This has fixed many a timing problem related to adding upgrades to your A8.
  11. You also might want to try SHIFT+CTRL+V when you paste it into the editor. That will remove any formatting and only paste it as plain text.
  12. I promise this will be my last one for a while. In this proposal no inversion of the SIO data is required, thus allowing the firmware to maintain compatibility with the old and new hardware. Although I believe the isolation will be better in the previous diagram with less tendency to back feed when FujiNet is off. However not having a real circuit setup to test, this one might be perfectly good as well. It does require an enable, although that could be done by using the FujiNet power as the gating signal. If the switch enable is handled by an IO pin, then the diode could be eliminated - in fact that may be preferred so that FujiNet SIO coms are only present when needed in order to avoid all conflicts.
  13. I agree 👍 . And because of all the activity, it tends to keep pushing other stuff very quickly off the first page.
  14. I did a bit more thinking about SIO isolation and came up with this as a possibility... This by far would be the simplest and cheapest solution ($0.78 for two 74HCT4066 chips), but wouldn't work out of the box for the present FujiNet design, since it requires inverted SIO data from FujiNet. Although that would be a fairly simple firmware change, it would break compatibility with older version hardware. You'll notice that it also gets rid of the diode in series with the DATA-IN line, since that would no longer be required.
  15. I was having a private discussion with Mr Robot about the following, and thought it might be good to share this idea over here. Topic: SIO noise issue when FujiNet switched off booting. What about disconnecting the analog connection to the SIO Audio-Input with an analog switch such as the CD4066 (or better yet the newer 74HC4066). These bi-directional switches will pass either analog or digital information. When the CTRL input is high, the analog switch will be closed. Think of it like a relay. Since there are 4 switches in the 74HC4066 package, the other 3 might be useful for something as well (substitute for individual gate in 74LS07) . Here's an example as to how that might be applied. Still one left over analog switch 🤔 . EDIT: I stand corrected, apparently the strange high pitched noise occurs when FujiNet is powered ON and booting a device. So in that case maybe the audio going to the SIO audio input can be disconnected during this booting state instead of when it's powered off, as I showed it above. EDIT2: The 74HCT4066 might be a better choice when the CTRL signal is less than 5V. Also another interesting variant would be the 74HCT4053 which has 3 x SPDT switches instead. And last but not least, two 4066 chips could be used to simply disconnect everything between FujiNet and the SIO as Mr Robot was suggesting, by using them as parallel connected switches (you would want pull-ups on the FujiNet side). Additional note - the switch IC that Mr Robot linked to would also work quite well and is capable of both digital and analog switching, but is a considerably more expensive chip due to its extremely high speed signal spec which would not be required for SIO.
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