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Serial to USB — Parallax Forums

Serial to USB

CraXzCraXz Posts: 3
edited 2008-12-09 08:21 in BASIC Stamp
Hi,

I am having a problem with a USB to serial connection, The serial port is detected by windows and works fine with different RS232 programs.
When I am using the self created cable on my BASIC Stamp 2 Module the program doesn't see the board.
The only thing i get is an echo, I have seached this forum for similiar problems, and I know that not al cables work because of the DTR signal ( Handshaking signal ).
I have also read that almost all FTDI chips should wordt with the parallax drives.

For my own serial/USB cable I am using a FT232BL chip. This chip has the standard RX and TX pins. Like i said before, these pins work great on different applications.
This chip also has the DTR pin on it, The only thing is, is that this pin is inverted.

I have tried different setups, With an MAX232, without it, With Transistors and without them, I also tried to invert the DTR line with an inverter. But all these diffirent settings gave me the same result.
I also tried diffirent drives, I tried the officals drives and the parallex drives, But I am shure that the drives aren't the problem.

When buying a development board they also use the FTDI chip, But this time they use the FT232RQ, Should i give this chip a try or does anyone has encounterd these problems before?

Hoping for an awnser







Comments

  • allanlane5allanlane5 Posts: 3,815
    edited 2008-12-08 18:12
    Your "Self-created cable" DOES have TX, RX, GND, and DTR, right? And it's a "straight-through" cable, not swapping TX/RX, right?

    I'm not sure what you mean by an "inverted DTR signal". That assumes you know which voltage is actually "Active".
  • CraXzCraXz Posts: 3
    edited 2008-12-08 18:21
    The USB to Serials cable works. But not with the basic stamp. The DTR signal is an inverted pin on the FT232BL chip.
    I have searched some more around the web and i figured out that u need to place a 12.2K resistor in the EEDATA pin on the FT232BL chip.
    I don't think that this solves the handshaking problem with the basic stamp program. Because windows sees my usb/serial cable as a working convertor.

    The basic stamp program also reconises my cable as an com port. but al i get is an echo, so the problem is not in my convetor but in the DTR ( Handshake ) signal

    I u used my own serial/USB cable before with a visual basic program. Then i had no problems with sending and getting data. ( I didn't use the DTR pin then ).
    The problem i got is that i need to handshake with my basic stamp, and i need to do that with the DTR pin, But somehow i can't get this working.
  • allanlane5allanlane5 Posts: 3,815
    edited 2008-12-08 20:05
    An off the shelf FTDI USB to Serial cable costs like $20, so I'm not sure what you're trying to achieve with your home-made cable.
  • FranklinFranklin Posts: 4,747
    edited 2008-12-09 02:00
    The fact that the computer sees the FTDI chip as a serial connection in no way means the stamp does. You will probably have to scope the data comming out to see if the pins are supplying what you need and that the timing is correct. Unless this is a learning experience just buy a proper cable and if this is a learning experience then you are (learning that is)

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    - Stephen
  • CraXzCraXz Posts: 3
    edited 2008-12-09 08:21
    Well the fact is that i am creating my own microbasic stamp delevopment board. But i want to build the FTDI chip on my own print. As My board works great. I can use al ports an its a working development board. So i want to test my own cable and put this FTDI chip on my own basic stamp board. So that is where I am going. I think i am going to try to order a new FTDI chip that is also used on the USB development board from parralax.
    ·
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