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Is this right? Schematic for FTDI to BS2P40 — Parallax Forums

Is this right? Schematic for FTDI to BS2P40

W9GFOW9GFO Posts: 4,010
edited 2012-08-22 14:27 in BASIC Stamp
This is my first time messing with an FTDI chip. I have tried to figure out the proper wiring using a combination of the QuickStart schematic, USB BOE schematic and the Bs2P40 schematic. Unfortunately, none of them quite exactly match what I need so I am unsure if I have done it correctly.

Comments are appreciated.

attachment.php?attachmentid=94971&d=1345243408

Comments

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2012-08-17 19:56
    Rich,

    The safest thing to do would be to compare yours with the BOE USB schematic:

    -Phil
  • W9GFOW9GFO Posts: 4,010
    edited 2012-08-17 20:17
    That is exactly what I did. The BS2P40 seems to be slightly different in that there is no data sheet for it specifically. I had to use the SX 48 part and rename/number all the pins. Lots of opportunity for errors I think.

    Also, the BOE schematic shows test left open. The data sheet says to ground it and the QuickStart shows it that way. Why is it not grounded on the BOE?
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2012-08-17 20:21
    Rich,

    The serial interface to all of the BASIC Stamps should be the same, else how could they plug into the BOE and be expected to work? If you're interfacing directly to an SX48, though, things will definitely be different.

    -Phil
  • W9GFOW9GFO Posts: 4,010
    edited 2012-08-17 20:41
    The BS2P40 schematic shows a module instead of the actual TQFP chip. The data lines go through other "stuff" before reaching the chip.

    I think you know, the BS2P40 is an SX48 chip. I can find no schematic or data sheet for the BS2P40 flavored SX48 - other than the drawing that is on the BS2P40 module.

    I was hoping someone knowledgeable could double check my schematic for peace of mind.
  • W9GFOW9GFO Posts: 4,010
    edited 2012-08-17 21:18
    I just realized - I am sure the schematic is not correct since the BOE example is meant to mimic the old serial interface to connect it to a module.

    I need to find out what is the minimum required to go from the FTDI directly to the chip - not a module.

    Just to be extra clear, I want to have the FTDI and the BS2P40 (chip, not module) right next to each other on the same PCB.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2012-08-18 08:09
    chip, not module
    Oh, that's a different story. In that case replace the transistor inverters with 74LVC open-drain non-inverting buffers, powered from VCCIO. RxD will be pulled up to VCCIO; RX, to Vdd. Take a look at the schematic for the MoBoStamp-pe (#28300) for the full story. You also need to create a loop-back from RX to TX, but the MoBo includes a way to disable it.

    -Phil
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2012-08-20 13:53
    I think I have provided the needed information via another channel. If not, please let me know. Didn't realize you had this thread originally.
  • RobotWorkshopRobotWorkshop Posts: 2,307
    edited 2012-08-22 14:27
    If it helps you can checkout the schematic I made for a board using the BS2p40 OEM chip and a MAX232 chip

    http://www.robotworkshop.com/robotworkshop/projects/parallax/BS2p40OEMschematic.pdf

    Robert
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