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Posted - 30 Apr 2002 :  16:37:25  Show Profile  Email Poster
Bitsy Personality Board for BitsyXb, BitsyX, Bitsy Plus and Bitsy
Schematic and Parts List

The schematic for the Bitsy Personality Board is supplied as a reference design.

There are two population options for this board: CF socket and 10/100BT Ethernet. Standard evaluation systems ship with the CF socket installed and Ethernet components removed.

See the notes below for details about compatibility between versions of the personality board and members of the Bitsy family.

Quad UART Design (New!)

We have a reference design for a personality board that sports 10/100 Ethernet and a quad UART. See topic 1293 for details.

Revision B
Shipped with BitsyXb development systems.

  • Socketed battery for real-time clock
  • Can be manufactured with RoHS processes

  • Revision A
    Shipped with Bitsy Plus, BitsyX and BitsyXb development systems.

    Acrobat Schematics (.PDF, 2pp, 150kB)
    ORCAD Layout (.MAX, 232kB)
    ORCAD Schematics (.OBJ, .DSN, 242kB)
    Mechanical and assembly drawings (topic)
    Bills of Material/Parts List: Compact Flash build, Ethernet build (PDF, 2MB)

    If you are developing an Ethernet personality board, we suggest you follow the layout recommendations suggested in this Intel app note: Intel site, ADS local copy (PDF 183kB).

    Known issues:
  • See Personality Board topic for basic issues.

  • Ethernet sometimes does not connect (topic 409) (see below for fix)

  • SPI TX and RX signals on J3 are reversed (see topic 679)

  • Revision 2 (Not for new designs)
    Shipped with prototype Bitsy Plus systems.

    Rev 2 schematic (PDF, 1pp, 83kB)

    Known issues:
  • Ethernet sometimes does not connect (topic 409) (see below for fix)

  • SPI TX and RX signals on J3 are reversed (see topic 679)

  • Voltage sensing for CompactFlash does not work (details)

  • Does not include CompactFlash power control interlock(details)

  • Revision 1 (Not for new designs)
    Shipped with Bitsy development systems.

    Rev 1 schematic (PDF, 1pp, 90kB)
    Mechanical and assembly drawings (topic)

    Known issues:
  • Battery charger does not work. It is not populated. D3 is stuffed with a shunt.

  • Header J3 matches the Rev B Bitsy and doesn't reflect the changes made in the Rev C Bitsy. SMTIO2 and SMTIO2 (PC6 and PC7) are not available at J31 of the personality board.

  • See Personality Board topic for basic issues.

  • The full part number for U5 is 93LC46BX

  • Description for J31 should read "Spare UCB1200 I/Os"

  • The node between R20 and R21 (Ethernet transformer) should be tied to 3.3V

  • Either R16 or R17 (Ethernet IRQ) may be populated, but not both.

  • Same for R4 and R5 (IrDA power).

  • Voltage sensing for CompactFlash 3.3V does not work (details)

  • ------------------
    ADS Knowledge Base

    Edited by akidder 2-Jul-2002: UCB12000 -> UCB1200
    Edited by akidder 25-Nov-2002: Add link and text for rev A design
    Edited by akidder 19-Dec-2002: Add link for rev 2 design; move all rev 1 known issues to this page from user manual page
    Edited by akidder 29-Jan-2003: Add bills of material for rev A
    Edited by akidder 13-Mar-2003: Add link about rev 2 Ethernet; place rev A schematic first
    Edited by akidder 27-May-2003: Update layout; add note about what product each personality board was used with
    Edited by akidder 3-Jun-2003: Note SPI signal reversal on rev 2 an A boards
    Edited by akidder 3-Jun-2003: Add link to Intel app note re: Ethernet signal layout
    Edited by akidder 10-Jun-2003: Add notes about voltage sensing, 3.3V CF power
    Edited by akidder 23-Sep-2003: Add link to rev A assembly drawing
    Edited by akidder 23-Dec-2003: Add link to quad UART design
    Edited by ctacke 16-Jan-2004: Add link to ORCAD Schematic for RevA
    Edited by akidder 1-Nov-2006: Corrected rev A schematic; incorrect PDF had been linked from this page since Apr-2006.
    Edited by akidder 5-Dec-2007: Add note about rev B


    1519 Posts

    Posted - 02 Jul 2002 :  11:50:19  Show Profile  Email Poster
    Rev. 1 Corrections

    The following are additional corrections and notes about the rev 1 Bitsy Personality Board schematics:

    • Pull the W/R signal (U3.36) up to 3.3V (the schematic erroneously shows it pulled down)

    • Tie TPICT to 3.3V through a 0.01uF capacitor for proper high-frequency bias

    • Ethernet drivers currently use /EXT_IRQ1

    • If you populate the Ethernet circuit, tie the /CARDBDET1 and /CARDBDET2 signals to ground. ADS drivers use the card detect signals to establish that an Ethernet personality board is connected to the Bitsy.

    Drew Kidder
    ADS Technology Transfer

    Edited 25-Nov-2002: Note that these comments are for Rev 1 schematics.
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    1519 Posts

    Posted - 25 Nov 2002 :  12:06:10  Show Profile  Email Poster
    Rev. A Schematics Posted

    We have posted the Rev A schematics for the Bitsy Plus Personality Board reference design. This board is part of standard Bitsy Plus evaluation systems.

    Prototype Bitsy Plus systems shipped with Rev 2 Personality Boards. Schematics are posted above.

    Edited by akidder 19-Dec-2002: Post rev 2 schematics and eliminate link to request them.
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    1519 Posts

    Posted - 20 May 2003 :  13:23:08  Show Profile  Email Poster
    Clarification: "Rev. C"

    There are several references to "Rev. C" around the resistors connected to J3. "Rev. C" refers to the Bitsy. Removing these resistors allows us to adapt revision A Personality Boards for use with the older Bitsy systems.

    Personality boards for use with Bitsy Plus and BitsyX systems should include the resistors indicated for the Bitsy Plus.
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    1519 Posts

    Posted - 22 May 2003 :  14:54:14  Show Profile  Email Poster
    Rev. 1 Correction: USB Function (Upstream) Port

    This note applies only to rev 1 Personality Boards that were shipped before October 2002. Rev 1 personality boards are used only with Bitsy development systems.

    USB function port pull-down resistors R45 and R46 should be 470k instead of the 15k resistors populated on the board. This can prevent Bitsy systems from communicating successfully with some PCs.

    Resistors R45 and R46 are located on the underside of the board near the USB connectors. If your PC does not acknowledge that a Bitsy system is connected, you might try removing these resistors.
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    1519 Posts

    Posted - 06 Jun 2003 :  16:37:34  Show Profile  Email Poster
    Recommendation: Ethernet Circuit Layout Guidelines

    If you are planning to use the Ethernet circuit in your product, we recommend you follow the design layout guidelines we've added to the initial post in this thread (see the link to the Intel app note).
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    1519 Posts

    Posted - 10 Jun 2003 :  17:01:30  Show Profile  Email Poster

    Rev 2 Design Issue: 3.3 and 5V Power Can be Enabled at Same Time

    The Bitsy, Bitsy Plus and other SA1111 products can connect both 3.3 and 5V to the CF slot power simultaneously. Some operating system and boot code builds momentarily enable both power supplies. This can cause boot and hardware failures by shorting the 3.3V and 5V supplies together, especially on systems that use transistors that switch slowly.

    Products Affected
    • Bitsy Plus with rev 2 Personality boards

    • Systems connected to custom personality boards

    • The SA1111 can be initialized such that both the 3.3V and 5V power signals are enabled at the same time (/CARDBON_3P3V and /CARBON, respectively).

    • This problem manifests in systems that use transistors with slower switching times (usually higher-current parts). Systems with fast transistors may not ever see this problem, as on-board capacitance can cover the momentary short. The standard Bitsy Plus is the only off-the-shelf ADS system that exhibits this issue. However, it may affect customer personality boards.

    • Past builds of CE and its boot code set the data direction of the SA1111 GPIOs before setting your initial values. Updates to the builds now set the initial values of the GPIOs before configurint them as outputs.

    • In addition, numeric revisions of the Bitsy Plus (prototypes) did not include pull-up/down resistors. The transistor inputs floated and could mistakenly turn on during board initialization.

    1. Update boot code and operating system.
      CE builds that incorporate a software fix include the following:
        Bitsy Plus
        Graphics Master

      CE boot code that incorporate a software fix include the following:
        Bitsy Plus
        Graphics Master

    2. Remove power transistor for voltage not used. Set CF port to a fixed voltage.

    3. Design a hardware interlock so only one voltage can be selected at a time. Include pull-up/down resistors to turn off transistors during system intialization.
      The Bitsy Personality Board rev A schematics illustrate one such solution.

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    1519 Posts

    Posted - 10 Jun 2003 :  17:09:47  Show Profile  Email Poster

    Rev 1 and 2 Design Issue: CF Voltage Sensing

    Revs 1 and 2 of the Bitsy Personality Board do not support voltage sensing for CompactFlash(CF) cards. You must select the voltage to use in software. Rev A corrects this issue.

    Since the CF socket on the Personality Board accepts only 5V-tolerant cards, there is no risk of damaging a 3.3V-only card, as it won't fit in the socket. However, 3.3V CF cards will consume more power than necessary if run at 5V.


    For systems with rev 1 or 2 of the Bitsy Personality Board you can do one or both of the following:

    1. Remove the power transistor for the voltage you won't be using.
    See this personality board issue for more details about why this may be important.

    2. Have the operating system set the voltage for the card to a fixed value.
    See the following for details.

    Fixed Card Voltage, Windows CE

    In CE, you can use the following entries to set the card voltage. Since the CF socket is for 5V tolerant cards, ADS recommends setting the voltage to 5V unless you are certain that all cards inserted will work at 3.3V.
    0xC0000F10 0x00000000 ; [00=5V] 01=3.3V

    "Socket2Power"=dword:0 ; 0=5V card, 1=3.3V card, other=automatic

    Fixed Card Voltage, Linux

    In Linux, you can modify the kernel to select the voltage you plan to use.

    If you are designing your own personality board...

    The CARDBVS1 and CARDBVS2 signals must be pulled up to Vddx (not CARDBVCC) for correct operation.

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    1519 Posts

    Posted - 17 Jul 2003 :  10:10:01  Show Profile  Email Poster

    Design Alert: BitsyX Ethernet Flicker

    Some displays flicker when Ethernet is in use on the BitsyX using the rev A Bitsy Personality Board. You must change the system bus timing (Linux kernel or CE adsload.hwt) and change a resistor on the personality board to eliminate the flicker.

    BitsyX systems that utilize Ethernet should change the pull-up resistor(RP4G) for CARDBWAIT from 10k to 4.7k ohm. This change can be accomplished by replacing RP4 or piggy-backing another 10k resistor pack on RP4.
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    1519 Posts

    Posted - 29 Aug 2003 :  14:01:14  Show Profile  Email Poster
    Design Alert: RTC Battery Power

    The RTC chip requires both main and backup power to operate correctly. Connector board designs should always supply power on the BATPOS input pin (J3.50), even if it is only Vddx(3.3V) looped back from J10.

    Reasons to have a functioning RTC on your system:
    • The RTC keeps better time than the CPU clock

    • The RTC can supply correct time when waking up from Sleep mode

    • Some OS builds will fail to boot if they cannot communicate with the RTC
    For designs that use no personality board, ADS can populate an on-board diode that supplies current to the BATPOS input. This diode is not normally populated because the diode reverse leakage current can prematurely drain coin cell batteries.
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    1519 Posts

    Posted - 10 Nov 2003 :  16:28:19  Show Profile  Email Poster

    Design Recommendation: Add Capacitance to Vddx

    If you are designing your own personality board, you might consider adding capacitance to Vddx(3.3V). We recommend adding a 330uF, 6V tantalum. This can help prevent the 3.3V PCMCIA reset issue described at topic 884 in rev A and earlier BitsyX systems.

    This is change is only necessary if users may insert unspecified cards into your BitsyX device in the future.
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    1519 Posts

    Posted - 20 Nov 2003 :  18:19:44  Show Profile  Email Poster

    Design Alert: Ethernet Crystal Caps

    If you plan to implement an Ethernet personality board design based on rev A or earlier, add capacitors between each leg of the Ethernet crystal and ground. This change appears to resolve the occasional connectivity problem described in topic 409.

    If you are experiencing problems with your existing systems(s), you can return the systems to ADS for repair or perform the rework yourself. Here's a diagram that illustrates what the rework looks like on rev A personality boards (*): GIF 13kB. You must scrape away the solder mask to solder the capacitors to the ground plane.

    SMSC recommends 30pF but we have found that 22 and 33pF caps work well and are more readily available in the market. We use 33pF 50V 0603 caps on our products (e.g. Panasonic ECJ-1VC1H330J).

    (*) Rev 2 board rework is slightly different, as there isn't a ground connection near the lower capacitor. You must run a wire from the lower cap to the upper one to get a good ground. GIF 7kB

    Edited by akidder 6-Jan-2004: Add part numbers and rework details.
    Edited by akidder 21-Jan-2004: Add notes about rev 2 boards.
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    1519 Posts

    Posted - 23 Dec 2003 :  12:17:24  Show Profile  Email Poster
    Quad UART Design

    We have published a reference design for a personality board that sports 10/100 Ethernet and a quad UART. See topic 1293 for details.
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    1519 Posts

    Posted - 23 Jan 2004 :  16:14:16  Show Profile  Email Poster
    ORCAD Schematics and Layout Files

    We've added the ORCAD files used to design the personality board. These are a useful starting point for new designs.

    Make sure to incorporate the various fixes defined in this posting, as the schematics posted are of the existing product and do not correct the issues we've identified.
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