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Re: RS232 Again?

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  • Jeff Jonas
    ... I m not at home this week so I can t check what parts/boards/assemblies I have but there are many lovely choices - the Adafruit FTDI friend converts TTL
    Message 1 of 12 , Jul 12 1:01 AM
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      > This is where you can find some info about the
      > Seagate serial port being only TTL

      I'm not at home this week so I can't check what parts/boards/assemblies I have but there are many lovely choices

      - the Adafruit "FTDI friend" converts TTL serial to USB, so it naturally works with Linux, Windows, OS/X, etc. There are several variations of the FTDI chip board, the most important options being jumpers for power source, 3.3 or 5V serial, and how many signals are available (the FTDI chip offers a lot for handshaking and "bit banging")

      - there are several MAX232 chips from which to choose. The most basic converts 5V TTL to RS232 using 4 external capacitors. Others allow 3.3V logic and/or no external capacitors. For breadboarding and experimenting, I prefer the pre-assembled postage stamp size boards, available from many sources.

      --jeff Jonas
    • joshbensadon
      ... I recently bought 5 Maxim RS-232 chips from China, very cheap. But I got burned (literally). Those chips had some defects. They would get extremely hot
      Message 2 of 12 , Jul 12 6:27 AM
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        --- In midatlanticretro@yahoogroups.com, "Jeff Jonas" <jeff_s_jonas@...> wrote:
        >
        > - there are several MAX232 chips from which to choose. The most basic converts 5V TTL to RS232 using 4 external capacitors. Others allow 3.3V logic and/or no external capacitors. For breadboarding and experimenting, I prefer the pre-assembled postage stamp size boards, available from many sources.
        > --jeff Jonas

        I recently bought 5 Maxim RS-232 chips from China, very cheap. But I got burned (literally). Those chips had some defects. They would get extremely hot and pop. I tried some Intersil chips from my old (diminishing) stock pile, no problem.

        :)J
      • dfnr2
        ... The *-232A versions are easier to work with and require only 0.1uF caps. New chips from reputable vendors can be had for a little over $1:
        Message 3 of 12 , Jul 12 7:40 AM
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          --- In midatlanticretro@yahoogroups.com, joshbensadon <no_reply@...> wrote:

          > I recently bought 5 Maxim RS-232 chips from China, very cheap. But I got burned (literally). Those chips had some defects. They would get extremely hot and pop. I tried some Intersil chips from my old (diminishing) stock pile, no problem.
          >
          > :)J
          >

          The "*-232A" versions are easier to work with and require only 0.1uF caps. New chips from reputable vendors can be had for a little over $1:

          http://www.mouser.com/Semiconductors/Interface-ICs/RS-232-Interface-IC/_/N-45lx1Zscv7?P=1yztkj3Z1z0xwq2Z1yzrawtZ1z0y3waZ1z0z44dZ1z0y33tZ1z0y33vZ1yzspjfZ1z0xuzo&Keyword=232a&FS=True&Ns=Pricing|0

          Dave
        • Mike
          From time to time, those RS232 to TLL adapters come in handy. I use the MAX202 instead of MAX 232, as it is a little easier to deal with. This single sided
          Message 4 of 12 , Jul 12 8:07 AM
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            From time to time, those RS232 to TLL adapters come in handy. I use the MAX202 instead of MAX 232, as it is a little easier to deal with.

            This single sided PCB I designed for the SCELBI does essentially what you need, It does have an extra flipflop needed for the SCELBI TX interface that can be bypassed (leave off the 7474 and jumper pin 9 to 13).

            http://www.willegal.net/blog/?p=4459

            I originally did a version of the board without the flip flop, that I used to reprogram a Sony CRT a while back. That is probably exactly what you need, but I don't know where the artwork is, at the moment.

            One of my PS/2 to ascii keyboard adapters could also be adapted, by leaving off the micro-controller and connecting directly to where the TX and RX pins on the micro-controller would normally be.

            http://www.willegal.net/appleii/appleii-kb-int.htm

            If you are familiar with AVR programming, the PS/2 adapter could also be repurposed as a parallel to RS232 converter (paper tape reader?), but that is another story.

            regards,
            Mike W.


            --- In midatlanticretro@yahoogroups.com, joshbensadon <no_reply@...> wrote:
            >
            > --- In midatlanticretro@yahoogroups.com, "Jeff Jonas" <jeff_s_jonas@> wrote:
            > >
            > > - there are several MAX232 chips from which to choose. The most basic converts 5V TTL to RS232 using 4 external capacitors. Others allow 3.3V logic and/or no external capacitors. For breadboarding and experimenting, I prefer the pre-assembled postage stamp size boards, available from many sources.
            > > --jeff Jonas
            >
            > I recently bought 5 Maxim RS-232 chips from China, very cheap. But I got burned (literally). Those chips had some defects. They would get extremely hot and pop. I tried some Intersil chips from my old (diminishing) stock pile, no problem.
            >
            > :)J
            >
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