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Trying to find USB interface — Parallax Forums

Trying to find USB interface

aviator3.1aviator3.1 Posts: 20
edited 2010-01-15 20:45 in BASIC Stamp
I'm working on a project and have moved all my components to my own PCB board including the BS2. I want to be able to directly program the BS2 while it is on my own board and not have to move it over to the Discovery Board to program it. Another reason I want to have a USB interface on my own board is so I can read all the outputs on my desktop while the chip is running. I was looking at USB2SER Development Tool Item code 28024, but it says in the description that I cant use this to program the BS2 since

"Programming a BASIC Stamp from a USB Port
The USB2SER is not able to program BASIC Stamps. BASIC Stamp modules require an inverted signal. If
you need to program a BASIC Stamp, use the Parallax USB to Serial (RS-232) Adapter (#28030)."

What I'm getting from this is that I need to get the RS-232 adapter instead and wire it up as shown below.><table border=Image Attachment :
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Comments

  • aviator3.1aviator3.1 Posts: 20
    edited 2010-01-15 16:49
    I would like to avoid the whole RS-232 idea and use USB directly. I would like to find a way or product that will function the same way as the USB interface on the Discovery Board. Any ideas would be greatly appreciated.
    -Thanks
  • Mike GreenMike Green Posts: 23,101
    edited 2010-01-15 17:05
    The schematic for the USB Board of Education is available via a link on the Parallax webstore page for the product. You could duplicate the circuit if you want. It would be easier and cheaper to buy one of the adapters (#28030), remove the DB-9 socket, and wire the adapter directly into your circuit as shown in the diagram you attached.

    www.parallax.com/Portals/0/Downloads/docs/prod/boards/BOE_USB_D_Schematic.pdf
  • allanlane5allanlane5 Posts: 3,815
    edited 2010-01-15 17:29
    The BS2 is 'natively' programmed using RS-232 -- so really there's no way to "avoid the whole RS-232 idea". The simplist approach is to make a small 4-pin MOLEX connector on your board (TX, RX, ATN, Ground), and attach a small 'dongle' to that to connect to a DB-9, then use a $20 USB-to-RS232 adapter to connect to the other side of the DB-9.

    This IS in fact the way the USB interface on the Discovery board works, except the USB to 4-pin interface is replaced by an FTDI USB chip and wire on the board. I suppose you could pay the extra bucks to have the FTDI USB interface chips on your own board -- but really, 4-pins and a reuseable adapter is WAY cheaper (and easier to get right) than a USB interface installed on every one of your target boards.
  • aviator3.1aviator3.1 Posts: 20
    edited 2010-01-15 17:31
    So your saying to unsolder the DB-9 socket and just wire the pins directly to my board as if the socket where still there?

    Thank you Ill give it a try
  • allanlane5allanlane5 Posts: 3,815
    edited 2010-01-15 17:51
    Wait -- you ALREADY have a DB-9 on YOUR board, wired correctly?

    Then all you need IS a $20 or less USB to RS-232 adapter module -- it's gonna cost WAY more than that to re-invent the wheel.

    And the USB2SER adapter STILL isn't going to work -- the BS2 requires RS-232 signalling levels, +- 3 volts. The USB2SER is TTL only, as I understand it.
  • JDJD Posts: 570
    edited 2010-01-15 20:45
    Aviator3.1,

    That is correct, the USB2SER is used for communication only not for reprogramming. The USB to Serial adapter (#28030)·is the far easier way of converting serial to USB; however if you want build the USB circuit, than Mike's suggestion to use the BOE schematic is going to be the best example to follow.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Respectfully,


    Joshua Donelson
    www.parallax.com
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