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DB9 and max2322 circuit? Maybe rs232 power also — Parallax Forums

DB9 and max2322 circuit? Maybe rs232 power also

rwgast_logicdesignrwgast_logicdesign Posts: 1,464
edited 2012-07-08 04:46 in Propeller 1
Im prototyping out a new propeller board for use with propalyzer as a genral purpose logic analyzer. Im thinking I would like to use a db9 connector instead of a prop plug header so the board is easier to work with and functions more like a tool than a dev board. So im thinking basically you wire the db9 pot to the level shifter then throw a .01uf cap 10k resistor and bjt transistor on dtr? Im wondering if there is a board that uses db9 for a programming connection and a max ic which has open schematic? The parallax schematics all seem to use some multiple rc circuit/transistor setup instead of a max ic, I have like 10 of these chips so id like to use it.

The next question I have is there anyway to power the board from the serial line? I looked it up and everything i found uses rts and dtr to power a few mA project. Just guestimating from my other overclocked prop boards this thing will need about 150-300mAs and the other issue is it needs DTR for reset. Im just trying to figure out the best way to power this thing without a wall adapter and was thinking drawing the power from the pc somehow would be great!

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2012-07-07 14:39
    RS232 can't supply any significant amount of power. You would be better off using a USB interface since USB can supply approx. +5V at up to 500mA. You will still need the DTR reset circuitry. Note that USB will normally provide up to 100mA once the USB device has been recognized by the PC. The USB adapter has to tell the PC that it might require up to 500mA for it to be able to draw that.

    FTDI has adapters that can provide 3.3V logic levels and up to 250mA at 3.3V here and they have other adapters that can supply 5V logic levels with up to 450mA at 5V here. With the higher current 5V adapter, you'll need 3.3K resistors in the transmit signal line (from the adapter) and maybe in the receive signal line as well (to the adapter). The reset circuitry should isolate the Prop's reset pin from the 5V DTR signal from the adapter.
  • msrobotsmsrobots Posts: 3,709
    edited 2012-07-07 15:08
    The PPDB has a MAX232 and you find everything you need in the docs...

    Enjoy!

    Mike
  • rwgast_logicdesignrwgast_logicdesign Posts: 1,464
    edited 2012-07-08 00:27
    ok guys thanks for the info ill figure out how to power the thing another way.

    i have pdb schematic its very useful. unfourtantely its not what im looking for in this instance its only a schematic of a serial port for extra com with the prop i.e mot for acual programing of the prop there is no dtr line and rc circut to pull rest. im looking to basically use a max232 in place of a prop plug.
  • TubularTubular Posts: 4,706
    edited 2012-07-08 04:46
    For a good example of a max3232/max232 see Phil's Propstick, scroll down the page and download the full documentation here:-
    http://smorgasboard.wikispaces.com/Designs
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