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DE2-115 Prop1 - a PropPlug replacement question — Parallax Forums

DE2-115 Prop1 - a PropPlug replacement question

pik33pik33 Posts: 2,366
edited 2014-08-08 14:07 in Propeller 1
I have no PropPlug, but DE2-115 has an RS232 input. I will try to interface this to a simulated Propeller, but I have a simple question:

Is it sufficient to simply invert DTR signal and connect this to RESn? Or do I have to make a pulse generator? If I have to make a pulse - how long that pulse has to be?

And another question: I don't know if these USB to RS232 dongles have DTR signal active. My board has an real RS232 port so I can use it without such converters, but I want to know if it is possible to use it that way.

Comments

  • Bill HenningBill Henning Posts: 6,445
    edited 2014-08-07 05:48
    See the prop manual, it has an RS232 circuit

    Just adapt the DTR section, you can use that with any usb-serial that has either DTR or RTS.

    Or use a PIC18F2550 as a USB/serial adapter, see the code on GadgetGangsters site (search for usb serial)

    pik33 wrote: »
    I have no PropPlug, but DE2-115 has an RS232 input. I will try to interface this to a simulated Propeller, but I have a simple question:

    Is it sufficient to simply invert DTR signal and connect this to RESn? Or do I have to make a pulse generator? If I have to make a pulse - how long that pulse has to be?

    And another question: I don't know if these USB to RS232 dongles have DTR signal active. My board has an real RS232 port so I can use it without such converters, but I want to know if it is possible to use it that way.
  • pik33pik33 Posts: 2,366
    edited 2014-08-07 06:02
    I don't ned a circuit now. The circuit is included in DE2-115. I have 4 FPGA pins, 2 inputs and 2 outputs, connected to DB9 slot via max3232
    Now I can connect this to a Propeller with Quartus - inside the FPGA.
    I only don't know if I can connect DTR directly to RESn (inverting only) - or if I have to make a pulse generator (all in FPGA).
    Having "blocked" a Propeller (see attachment) it is possible to make full Propeller environment with DE2-115 only
    prop_cycloneV.jpg
    1024 x 598 - 104K
  • Tracy AllenTracy Allen Posts: 6,664
    edited 2014-08-07 09:18
    RSTn needs a low-going pulse. A microsecond (or more) will do, as the Prop latches it internally. RSTn has to go back high in order for the Prop to exit reset.

    P.S. This link relays a comment from Chip Gracey about the required length of the reset pulse.
  • Cluso99Cluso99 Posts: 18,069
    edited 2014-08-08 14:07
    The reset pulse is triggered by the DTR signal going inactive active.
    At a ttl level, active is 0v, so you need to create the pulse on the low to high high to low edge of the ttl signal.

    I hope this helps. I now see that you are going to create this circuit inside the fpga connection.
    There are reasons behind this way, but that is not relevant to getting you running.

    The reason is that for PCs running Windows programs (might be the same for other OSes), when switching between programs, windows removes/resets DTR (and RTS). This way, after running a program that sets DTR (such as the download program), when you switch to another program windows resets DTR & RTS. Now you the next program starts, and provided it does not turn on DTR, everything is fine. You see, with this method you can switch between programs and DTR will not reset your program.
    This is why the propplug uses the cap and transistor circuit.

    Now, if you don't need to switch programs, then you can just use DTR directly.
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