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undo patch for 232 inversion?

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  • Jason Winningham
    Once upon a time, after I blew three 2n7000s, I retrofitted a MAX232 onto my T2 (beta A, I think). Scott helpfully supplied a patch command to allow my to
    Message 1 of 3 , Dec 6, 2007
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      Once upon a time, after I blew three 2n7000s, I retrofitted a MAX232
      onto my T2 (beta A, I think). Scott helpfully supplied a patch
      command to allow my to skip an internal inverter on port A.

      Now I want to back this out. I want to add port B, plus the config
      program won't talk to me (that inversion is still expected). I've
      got a new MAX232 circuit (complete with 7404 this time), all I need
      to do is un-flip that bit.

      So, Scott, what value do I PATCH to f9b0 to get things back to the
      original settings?

      -Jason
      kg4wsv


      > Well, there's the PATCH command... that *might* work. Let's see...
      > the byte is at 0xf9b0. For a Proto A board it should be 0x00 by
      > default. To make it not invert the signal you need to set it to
      > 1. So the on-air command (you did remember to set the AUTHLIST,
      > right?) would be:
      >
      > CMD PATCH F9B00101
      >
      > You just have to hope that nothing needed by the patch command
      > itself resides in that particular erase block! So you've got to
      > ask yourself... do you feel lucky? =]
      >
      > I've also heard that the MAX232 will tolerate having one of its own
      > outputs looped back to an input, so you could try that to add
      > another inversion.
      >
      > Also, just to clarify, only the TX side is inverted in software,
      > and only on port A. The RX side needs external inversion, either
      > through the 232 chip or the FET. Port B has no invert option, so
      > it always needs external inversion.
      >
      > Scott
    • Scott Miller
      From hw-ot2.h: 55 #define HWCFG (*(volatile unsigned char*)(0xf9b0)) 56 #define CFG_NO_TX_INVERT 0x01 57 #define CFG_DCD_ON_PTB1 0x02 58 #define
      Message 2 of 3 , Dec 6, 2007
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        From hw-ot2.h:

        55 #define HWCFG (*(volatile unsigned char*)(0xf9b0))
        56 #define CFG_NO_TX_INVERT 0x01
        57 #define CFG_DCD_ON_PTB1 0x02
        58 #define CFG_NO_SENSORS 0x04
        59 #define CFG_OPEN_SQUELCH 0x08
        60 #define CFG_1WIRE_RTS_SHARED 0x10


        So what you set before was the CFG_NO_TX_INVERT flag. If you want to
        clear it, you need to PATCH F9B00100 (the 01 after the address is the
        number of bytes to patch.)

        The other flags can be added together if you want to set other hardware
        options.

        Scott

        Jason Winningham wrote:
        >
        >
        > Once upon a time, after I blew three 2n7000s, I retrofitted a MAX232
        > onto my T2 (beta A, I think). Scott helpfully supplied a patch
        > command to allow my to skip an internal inverter on port A.
        >
        > Now I want to back this out. I want to add port B, plus the config
        > program won't talk to me (that inversion is still expected). I've
        > got a new MAX232 circuit (complete with 7404 this time), all I need
        > to do is un-flip that bit.
        >
        > So, Scott, what value do I PATCH to f9b0 to get things back to the
        > original settings?
        >
        > -Jason
        > kg4wsv
        >
        > > Well, there's the PATCH command... that *might* work. Let's see...
        > > the byte is at 0xf9b0. For a Proto A board it should be 0x00 by
        > > default. To make it not invert the signal you need to set it to
        > > 1. So the on-air command (you did remember to set the AUTHLIST,
        > > right?) would be:
        > >
        > > CMD PATCH F9B00101
        > >
        > > You just have to hope that nothing needed by the patch command
        > > itself resides in that particular erase block! So you've got to
        > > ask yourself... do you feel lucky? =]
        > >
        > > I've also heard that the MAX232 will tolerate having one of its own
        > > outputs looped back to an input, so you could try that to add
        > > another inversion.
        > >
        > > Also, just to clarify, only the TX side is inverted in software,
        > > and only on port A. The RX side needs external inversion, either
        > > through the 232 chip or the FET. Port B has no invert option, so
        > > it always needs external inversion.
        > >
        > > Scott
        >
        >
      • Jason KG4WSV
        ... Ah, now I know where to look in the future. Only there shouldn t be a future - if I need to do much more hacking, I ll get another T2. And probably a
        Message 3 of 3 , Dec 6, 2007
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          On Dec 6, 2007 11:48 AM, Scott Miller <scott@...> wrote:
           From hw-ot2.h:

          Ah, now I know where to look in the future.  Only there shouldn't be a future - if I need to do much more hacking, I'll get another T2.  And probably a DR135 to put it in. (:

          Got the PCB layout done for my MAX232/7404 board, need to etch one and build it this weekend.

          thanks Scott.

          -Jason
          kg4wsv
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