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SD2IEC - modifying a board, questions about two SD cards.

  • First of all, sorry for my English. And unfortunately I don't speak German.
    I'm planning to build a two-card SD2IEC, but I can't build devices using SMD parts - so I'm going to design another board for it, using, if possible, only one layer (I'll figure it out if I have a schematic). I have some questions about designing it:
    1. As I look to a Shadowolf's schematic here: http://www.pitsch.de/stuff/mmc2iec/index.htm#A11 there's a resistor R13 between PB2 and PA0 (IEC_ATN). According to 1.9 firmware config file, PB2 is an interrupt pin used by SD2 presence detect. Should this resistor be removed?
    2. There's a way to connect a PCF8563 RTC to I2C, as I think to mark file dates properly. Are there any schematics showing how to connect this?
    When RTC is powered up from circuit's power supply, it's OK, but after the power is turned off, RTC will loose its data. Will it be enough to connect CR2032 battery to RTC's Vcc thru 2 diodes (to avoid Vcc "charging" not rechargeable battery)?
    3. Are there any pins/pins+small logic on the SD card socket, which can blink LED when the card is in use? ;)
    4. I'm going to build it on small boards to fit it easily in some old modem case). How long uC-SD cable can be, to not worry about interferences?
    5. Should the IEC leads for Shadowolf's board be connected to two IEC connectors (like inside 1541)?


    Thanks in advance
    MCbx

  • 1. As I look to a Shadowolf's schematic here: http://www.pitsch.de/stuff/mmc2iec/index.htm#A11 there's a resistor R13 between PB2 and PA0 (IEC_ATN). According to 1.9 firmware config file, PB2 is an interrupt pin used by SD2 presence detect. Should this resistor be removed?


    Yes - the pads for that resistor were added to the PCB, but the resistor was meant to be left out. It was designed in in case there were problems with interrupt-based ATN handling, but was found not to be required after all so the pin was repurposed for the dual-SD-card-hack (now deprecated).


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    2. There's a way to connect a PCF8563 RTC to I2C, as I think to mark file dates properly. Are there any schematics showing how to connect this?


    I don't think so and I can't draw one right now.


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    When RTC is powered up from circuit's power supply, it's OK, but after the power is turned off, RTC will loose its data. Will it be enough to connect CR2032 battery to RTC's Vcc thru 2 diodes (to avoid Vcc "charging" not rechargeable battery)?


    Yes, that's the usual way to supply power to this RTC. You may want to use Schottky-type diodes (e.g. BAT85 or similiar) because they have a smaller voltage drop.


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    3. Are there any pins/pins+small logic on the SD card socket, which can blink LED when the card is in use?


    You could build something based on the clock line of the card.


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    4. I'm going to build it on small boards to fit it easily in some old modem case). How long uC-SD cable can be, to not worry about interferences?


    That depends on the cabling - some people have reported success with 30cm, others had trouble with just 10cm. Use a flat ribbon cable, don't leave out "redundant" GND or VCC lines.


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    5. Should the IEC leads for Shadowolf's board be connected to two IEC connectors (like inside 1541)?


    That's up to personal preference, the connectors of a 1541 are just wired in parallel after all.

  • First of all, sorry for my English. And unfortunately I don't speak German.
    I'm planning to build a two-card SD2IEC, but I can't build devices using SMD parts - so I'm going to design another board for it, using, if possible, only one layer (I'll figure it out if I have a schematic). I have some questions about designing it:

    First question: Why not take an already existing layout? It's one layer and no SMD.
    The only real difference is that it's using the LarsP-Variant sd2iec firmware due to some ports being used differently (and the LEDs being reversed polarity). But if you look at the Shadowolf version of the board (which is missing the external oszillator, so just look at the port connections) you can easily identify the differences.


    - The IEC-Bus uses different Pins.
    - The LEDs use different Pins (and they pull against GND for shadowolf, but against Vcc on LarsP)
    - The Device# and Disk Change jumpers/buttons use other Pins.
    - And yes, it uses a voltage divider instead of FETs...


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    5. Should the IEC leads for Shadowolf's board be connected to two IEC connectors (like inside 1541)?

    As you wish. It's probably easier to work with both a Floppy and a sd2iec if you have two connectors installed.

  • One more thing - I read somewhere that Shadowolf's IEC circuits (with MOSFETs) are more compatible while working with many IEC devices. And I have some questions about them:
    1. Is IEC_RESERVE pin (defined in config.h as IEC_SRQ) needed? In schematic, it's labelled like temporary.
    2. About MOSFETs, because I don't know much about them - what are non-SMD alternatives to IRLML2402? Will MOSFET with higher power (non-SMDs usually are) be good?

  • One more thing - I read somewhere that Shadowolf's IEC circuits (with MOSFETs) are more compatible while working with many IEC devices.

    I read that too, maybe Unseen can shed some light on this.
    I never used more then two devices on the IEC bus so far.

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    1. Is IEC_RESERVE pin (defined in config.h as IEC_SRQ) needed? In schematic, it's labelled like temporary.

    No, not really.

  • One more thing - I read somewhere that Shadowolf's IEC circuits (with MOSFETs) are more compatible while working with many IEC devices.


    With more than three or four original CBM drives (and probably other serial devices, although not any hardware that sd2iec runs on) connected to the serial bus the AVRs outputs are not strong enough to provide reliable signals on the bus - the additional MOSFETs of Shadowolf's design can pull "harder" on the lines and IIRC have been tested with up to 10 drives on the bus.


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    1. Is IEC_RESERVE pin (defined in config.h as IEC_SRQ) needed? In schematic, it's labelled like temporary.


    In theory it could be used for the C128's burst mode, but that is not implemented in sd2iec.


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    2. About MOSFETs, because I don't know much about them - what are non-SMD alternatives to IRLML2402? Will MOSFET with higher power (non-SMDs usually are) be good?


    Sorry, I have no clue about that - I'm primarily a software person.