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Proto board and regular serial interface instead of USB issue — Parallax Forums

Proto board and regular serial interface instead of USB issue

RaymanRayman Posts: 14,789
edited 2007-09-25 02:12 in Propeller 1
I had an extra proto board but no more USB interfaces to go with it, so I built the little circuit in the documentation to connect with a regular RS-232 serial port on my computer...

Strange thing is that it only works when directly connected to the port on the back of my computer!· When I try to bring it out with a regular 6' straight-through extension cable, it doesn't work (the Propeller Tool doesn't find it).

Isn't this strange?· Is the Prop Tool trying to connect at some insane speed that doesn't work over an extension cable?

I looked in all the documentation I have and can't find any mention of what rate the Prop and the Prop tool are communicating...

It's a bit inconvenient to crawl under the desk and hook it up right now, so I'd appreciate any suggestions!

Can I lower the com rate between Prop and Prop Tool?

Comments

  • Peter JakackiPeter Jakacki Posts: 10,193
    edited 2007-09-23 02:16
    Rayman,

    Why do you assume that it is a speed issue? The RS-232 drivers are normally only rated up to 115K baud and no way that would ever be a problem over 6' of cable.

    The most logical conclusion would be your "regular" cable, is there really such a thing? Make up your own or at least check the cable with a meter which is surely a lot less inconvenient then crawling under a desk.

    *Peter*
  • Ken PetersonKen Peterson Posts: 806
    edited 2007-09-23 02:20
    Rayman-

    Things to check:
    1. Is the cable good? Have you used it before?
    2. Are all of the lines connected in the cable, including DTR? Otherwise it won't reset the chip.

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    The more I know, the more I know I don't know.· Is this what they call Wisdom?
  • parts-man73parts-man73 Posts: 830
    edited 2007-09-23 02:43
    Definitely check that it's a straight through cable, perhaps it's a null modem cable???

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    Brian

    uController.com - home of SpinStudio
  • RaymanRayman Posts: 14,789
    edited 2007-09-23 02:52
    I double checked the cable. Even used a different one. It is straight through. But, it's pretty late here... Maybe I'll triple check tomorrow...
  • Graham StablerGraham Stabler Posts: 2,510
    edited 2007-09-23 08:02
    I'd be half expecting the cable to have a cross over so you end up with rx-rx and tx-tx

    Graham
  • deSilvadeSilva Posts: 2,967
    edited 2007-09-23 08:27
    Use a simple terminal program and send things to your prop
    - If you don't want to write a program just use an LED
    - Check the reset pulse! Sometimes funny connections are inside a sub-D plug wrt DTR, CTR, and RTS smile.gif
  • RaymanRayman Posts: 14,789
    edited 2007-09-23 13:51
    Very strange. Got same result with a different computer! Quadruple-checked cable and it is straight trough!

    I think I did find a fix though. I don't understand why, but adding a 0.1 uF cap between reset and ground solves the problem...
  • deSilvadeSilva Posts: 2,967
    edited 2007-09-23 15:05
    Has your reset logic really been o.k. from the beginning?
    This cap will most like extend the reset-down time. So it seems possible that your differenciating series cap in the DTR line was too small..
    Generally a 10nF + 10k high-pass at a transitor base is fine, as done on the demo board....
  • RaymanRayman Posts: 14,789
    edited 2007-09-23 17:13
    I just made the circuit exactly as it appears in the Proto Board documentation. I wonder if anybody but me actually tried it? Maybe everybody uses USB?
  • deSilvadeSilva Posts: 2,967
    edited 2007-09-23 23:03
    ? In the "Proto Board Documentation"? I can't find a serial adapter in it...
  • RaymanRayman Posts: 14,789
    edited 2007-09-24 00:35
    Sorry, It's in the "Datasheet", page 5.
  • BTXBTX Posts: 674
    edited 2007-09-24 11:37
    Hi Rayman.

    Modestly I suggest you to try the following:
    Rayman said...
    Strange thing is that it only works when directly connected to the port on the back of my computer!
    1-So, do a little code communicationg the propeller with the PC at 2400 bps sending some text lines.
    2-Use no cable to download the code to the pchip.
    3-Use hyperterminal to check the code and data sent with NO cable attached.
    4-Connect the cable after get all work and try again..

    5-If·still wont work, check the cable again and again, no proper shield could be the problem at high rate speeds. If this work at 2400 bps you're proving that.

    I used that circuit exactly as it appears in the datasheet , and it works fine for me. Do you assemble it more or less "appropriately" ?


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    Regards.

    Alberto.
  • RaymanRayman Posts: 14,789
    edited 2007-09-24 12:42
    BTX said...

    I used that circuit exactly as it appears in the datasheet , and it works fine for me. Do you assemble it more or less "appropriately" ?

    Did you do this with the Proto board?· How did you connect to the reset pin?· I had to run a jumper over to the Prop-Clip connection...
  • BTXBTX Posts: 674
    edited 2007-09-24 13:13
    NO Rayman...
    I mean I used the serial circuit to program the propeller...I assembled that with a pchip, xtal, eeprom, in a board.
    Point 2.3.2 in page 5. Schematic point 2.3.1 of pchip datasheet. I used a homemade 3 ft serial cable.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Regards.

    Alberto.
  • ForrestForrest Posts: 1,341
    edited 2007-09-24 17:06
    FYI that serial-Propeller circuit has gone thru at least 3 revisions. I believe the original version had (3) transistors and (10) resistors, and each time it was revised the part count dropped. What circuit revision are you using?
  • RaymanRayman Posts: 14,789
    edited 2007-09-24 17:56
    The one in the Datasheet v.0.3 It has 2 transistors.
  • IAN STROMEIAN STROME Posts: 49
    edited 2007-09-25 01:10
    Yes I'm using that one
    no probs,works absolutly fine with Hippy's VBLOADER, but not got it to work
    yet with DOS under FPC ( but that's my problem )
    Hippy I need your expertise,I've probably got a timing problem!!

    :- Wouldn't it be nice if the Wattage of a car stereo couldn't exceed the
    IQ of the driver.

    Regards to All
    Ian
  • hippyhippy Posts: 1,981
    edited 2007-09-25 02:12
    IAN STROME said...
    Yes I'm using that one
    no probs,works absolutly fine with Hippy's VBLOADER, but not got it to work
    yet with DOS under FPC ( but that's my problem )
    Hippy I need your expertise,I've probably got a timing problem!!

    Glad to hear my loader's working. As to expertise, you may be over-rating me, but you're welcome to run anything past me and I'll give it my best shot.

    A problem I found was that too long between any pulses and the Propeller timesout or something, communications is lost. I found the best thing was small buffers rather than large and keep the data churning out as quickly / as frequently as possible. In real world terms, keep the PropPlug blue Tx Led on as much as possible rather than pulse-gap-pulse.
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