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USB2SER the same as prop plug with different pinnout? — Parallax Forums

USB2SER the same as prop plug with different pinnout?

grindelgrindel Posts: 68
edited 2009-04-30 17:54 in Propeller 1
uhhh...the subject says it all: am I missing something?

Is the USB2SER (for sale now for $14) the same as prop plug with different pinnout?

Post Edited (grindel) : 4/30/2009 1:26:45 AM GMT

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2009-04-30 01:39
    No

    The USB2SER uses +5V logic levels and has one pinout.

    The PropPlug uses +3.3V logic levels and has another pinout.
  • grindelgrindel Posts: 68
    edited 2009-04-30 11:43
    The reason it came up is that I saw the Prop Protoboard (according to the documentation) had provisions for the USB2SER with no special current limiting resistor, it just switched around the pin outs. Looking at the USB2SER documentation, it looks like there are 150 OHM resistors on the TX and RX. Is that large enough? It just would surprise me that they would put it on the protoboard if it would fry the chip.

    I should have said, "Is it functionally the same, from a prop programming perspective, except for the pin out"

    Has anyone tried it?
  • ReiserificKReiserificK Posts: 24
    edited 2009-04-30 12:23
    I haven't, but I'd also be interested in finding out if it works
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2009-04-30 16:45
    The USB2SER has 1K resistors in series with its outputs, unlike the Prop Plug/Clip which uses 150 ohm. The 1K resistors allow the USB2SER to interface with the Propeller nicely, especially since the 5V VCCIO never really reaches 5V. However, 1K resistors will limit the bandwidth on these pins meaning the USB2SER will never realize the 3Mbps bandwidth.

    Almost forgot…the USB2SER was recently updated…so customers who purchased a newer unit will have the 150 ohm resistors. Again, due to the 5V VCCIO not being 5V (closer to 4V) the smaller resistors will be sufficient protection for 3.3V devices that have protection diodes on the I/O pins. I hope this helps. Take care.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Chris Savage
    Parallax Engineering
  • Tim-MTim-M Posts: 522
    edited 2009-04-30 17:11
    I thought the discussion was about the products...

    USB to Serial(RS-232) Adapter shown here:

    http://www.parallax.com/Store/Accessories/CablesConverters/tabid/166/CategoryID/40/List/0/Level/a/ProductID/378/Default.aspx?SortField=ProductName,ProductName

    vs.

    The USB2SER Development Tool shown here:

    http://www.parallax.com/StoreSearchResults/tabid/768/txtSearch/usb2ser/List/0/SortField/4/ProductID/32/Default.aspx
  • grindelgrindel Posts: 68
    edited 2009-04-30 17:54
    I was refering to the prop plug, seen here:
    http://www.parallax.com/StoreSearchResults/tabid/768/List/0/SortField/4/ProductID/398/Default.aspx?txtSearch=PROP+PLUG

    compared to the USB2SER, seen here:

    http://www.parallax.com/StoreSearchResults/tabid/768/txtSearch/usb2ser/List/0/SortField/4/ProductID/32/Default.aspx

    t'was a good deal on the USB2SER for $14...So of course I have one on order. We'll see if I have any issues, I am making my own board from soldered breadboard, so I can pick the pin out or add diodes or whatever it takes.

    Cris, just an observation: "Almost forgot…the USB2SER was recently updated…so customers who purchased a newer unit will have the 150 ohm resistors. Again, due to the 5V VCCIO not being 5V (closer to 4V) the smaller resistors will be sufficient protection for 3.3V devices that have protection diodes on the I/O pins. I hope this helps. Take care."

    The protoboard manual says nothing about protection diodes, and indeed, has nowhere to put them if they are really required for the new rev of USB2SER. Can you confirm that it needs the protection diodes? Do I need them both on the TX and RX sides? I wouldn't think it would need it on RX, but I just want to confirm.
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