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Prop not recognized — Parallax Forums

Prop not recognized

slosjoslosjo Posts: 25
edited 2007-09-26 22:57 in Propeller 1
Hello-

I am having a few issues with my propeller prototype board and was hoping·someone could help me troubleshoot. Yesterday, my propeller was being recognized and compiling normally. After a few program changes, I tried to compile and a message came up saying 'no propeller found on com port x'. After looking over my circuit and code·very carefully and trying to recognize the chip several times with F7, I came to the conclusion that the chip had been fried. Today, I had a·new propeller chip soldered·onto my prototype board. I again checked my circuit and code to make sure everything was ok, turned the board on for the first time since the new chip was installed and hit F7, and again got the same error message. Another thing to keep in mind is that I also connected a new proto board and it was recognized right away, thus ruling out a bad USB cable or other computer related issues. Please help me figure this out, I'm not sure what else to troubleshoot on the board.

P.S. FYI: there was no smoke or burning electronic smell yesterday

Thanks


Post Edited (slosjo) : 9/26/2007 6:49:37 PM GMT

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2007-09-26 18:47
    There's not much that has to work for a Propeller to be recognized by the Propeller Tool. You have to have power, well regulated and bypassed near the chip as is true for any logic. The serial connection to the PC has to be intact in both directions and the Reset line has to be triggered by asserting DTR as is shown in the various sample schematics. The PropStick ones (serial and USB) are good examples. The crystal is not used, so that doesn't matter. None of the other I/O pins should have voltages on them above +3.3V or below ground. The EEPROM isn't used for this function of the boot loader.

    It's odd that the board should work several times, then stop working and not work when a new Prop chip was substituted. Since the only other section of the circuit that's critical is the serial interface, I'd check that.
  • RaymanRayman Posts: 14,789
    edited 2007-09-26 18:49
    I guess the first thing to check is that Vdd=3.3V. Then, I guess make sure the reset switch didn't fail closed. I don't see what else could go wrong...
  • slosjoslosjo Posts: 25
    edited 2007-09-26 18:56
    Mike-

    With the power on, no pins are above 3.3 or below 0. As I said, a brand new proto board was recognized right away. I checked the continuity between the 4 pins on the prop plug and their destinations and there are no open circuits.


    Rayman: VDD is 3.3V, and yes the reset switch is still working normally.


    ·
  • rjo_rjo_ Posts: 1,825
    edited 2007-09-26 19:14
    slosjo,

    Do I understand you correctly... that you have designed your own prototype board and this is the one that is failing?
    What happens on the reset pin when you try to find the Prop?

    Rich
  • Fred HawkinsFred Hawkins Posts: 997
    edited 2007-09-26 19:34
    Tell us about how you power these boards. Are their power supplies the same?

    (Your first post sounds like what happens to a 9volt battery powered board, signaling that it is new battery time.)
  • slosjoslosjo Posts: 25
    edited 2007-09-26 19:46
    OK everyone let me clear a few things up:

    This is the parallax propeller prototype board on which I have designed somthing. I am using a Radio Shack 13.8 V power supply (the spec for the DC-DC converters on the proto board is something like a max of 27V input) so that should be ok, and yes I checked that it was putting out 13.8V and the second DC-DC was putting out 3.3V.

    If I put a DMM from ground to the prop plugs' RES or to the RESn pin on the prop(pin7) the results are:

    Turned on: 3.3V
    Pressing Reset Button: 0V
    Searching for prop: 3.3V and dosen't appear to go to 0 at any time
  • Thomas StickneyThomas Stickney Posts: 23
    edited 2007-09-26 20:15
    13.8 volts in is alot for a 5 volt regulator to handle, I use switching type DC adaptors of 7.5v to 9v.
    The voltage is more stable under various loads.
  • slosjoslosjo Posts: 25
    edited 2007-09-26 20:24
    There are 2 regulators on the proto board, one that takes the voltage from Vin(in my case 13.8) to 5, and the then the other takes it from 5 to 3.3. According to the data sheet for those regulators, the maximum difference between vin and vout for the LM1085CS-5.0 should be no more than 25V, and I am well within that spec.

    I also checked all of the Vdd pins on the prop, they are all at 3.3v when the board is on.·

    Post Edited (slosjo) : 9/26/2007 8:35:42 PM GMT
  • RaymanRayman Posts: 14,789
    edited 2007-09-26 22:18
    Well, you must be good at soldering to put in a new MCU... Maybe you could remove a loaded EEPROM from your other board and put it on this one and see if the Prop is working at all...
  • slosjoslosjo Posts: 25
    edited 2007-09-26 22:57
    good suggestion...I'll try that

    and no, i'm not that good at soldering to attempt that....but a guy that I know is
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