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Quickstart quirkiness — Parallax Forums

Quickstart quirkiness

simonlsimonl Posts: 866
edited 2012-06-27 11:02 in Propeller 1
I just bought 2 Quickstarts and see the same issue on both: When placed flat on the table or paper pad, the LEDs all flicker or light permanetly. If I lift the boards by the USB cable - keeping them flat - the LEDs go out. If I place them flat on my laptop, the LEDs stay off. And if I then run my finger across the header socket, the LEDs seem to light in accordance with where my finger is!

If any of the LEDs are on, I cannot program the Quickstart!

Anyone else see this quirky behaviour?

Comments

  • g3cwig3cwi Posts: 262
    edited 2012-06-23 14:00
    The sensitivity is pretty normal. I have not noticed the programming problem though.

    Cheers

    Richard
  • Duane DegnDuane Degn Posts: 10,588
    edited 2012-06-23 14:26
    As Richard pointed out the LEDs lighting is normal. It's due to the buffer used on the board so the LEDs don't interfere with the I/O pins in case you want to use the I/O pins for some other purpose.

    I also haven't had a problem programming a QuickStart when the LEDs are on and I haven't hear of this being an issue. There are other issues wth the QuickStart though.

    I've tried to gather some links to QuickStart projects in this thread. There's probably a link to discussion about the LED quirks somewhere in the thread.
  • jazzedjazzed Posts: 11,803
    edited 2012-06-23 15:48
    Which tools fail to program the Quickstart?
  • jmgjmg Posts: 15,183
    edited 2012-06-23 15:53
    simonl wrote: »
    If any of the LEDs are on, I cannot program the Quickstart!

    Classic floating CMOS, and here it may be that when 'on' they are actually oscillating on the edges at high frequencies, which I have seen can disturb some designs. Depends on the PCB, but high MHz can do funny things.

    If you feel like an experiment, grab a '541 with Schmitt trigger pins, and see if that makes a difference.
    Many octal parts have schmitt IPs, you just need to chase the fine print, and be brand selective.

    http://www.nxp.com/documents/data_sheet/74AHC_AHCT541.pdf

    If I was designing the Quickstart, I'd use a AHCT541 with an option to power the 'T541 from 5V, as the LED driver, to also give users a free 5V Out shifter, and allow better access to the Pins.

    If Parallax swap from Digikey 296-8335-6-ND to 954-74AHCT541PW118-CHP, they will actually save 1.08c, and make Quickstart more useful ;)
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2012-06-23 15:56
    The correlation of loading issues with the LEDs being lit is likely a random coincidence. See this thread that discusses QuickStart loading problems and the "magic resistor" solution:

    -Phil
  • simonlsimonl Posts: 866
    edited 2012-06-23 16:38
    Wow! Loads of response - thanks folks :) I'll take a look at the threads offered. I'm glad it's not just my Quickstart (QS) boards!

    @jazzed: None of the following IDEs could see either QS when the LEDs were on: PZST, Proptool, SIDE, ViewPort.

    Interestingly, once I got the QS programmed, laying it flat on the table or paper pad didn't interrupt the program.

    I can live with it - I just place the QS on my laptop or hold it at an agle whilst programming it - but it seems a bit odd that Parallax would allow this past QA, especially as it was originally intended as a demo board for potential commercial customers.
  • mindrobotsmindrobots Posts: 6,506
    edited 2012-06-23 16:52
    Simon, try the magic resistor!
  • jmgjmg Posts: 15,183
    edited 2012-06-23 17:13
    Phil Pilgrim (PhiPi) wrote: »
    The correlation of loading issues with the LEDs being lit is likely a random coincidence.

    Not entirely random, his observation is likely correct.

    The P3.0 issue is a Floating-Pin one, that sidetracks a boot flow, and if the stray field is strong enough to 'fire' LEDS, it will likely be strong enough to 'fire' P3.0, so I would expect a good correlation between the two.
  • simonlsimonl Posts: 866
    edited 2012-06-23 17:18
    Thanks all - wish I'd found the other thread sooner. I'll try the magic resistor between 33 & 38 and will post here again if I have further trouble.
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2012-06-23 20:35
    simonl,

    Just out of curiosity, what Rev letter are your QuickStart boards?
  • RaymanRayman Posts: 14,827
    edited 2012-06-24 04:56
    LEDs on could be related to the loading issue... The LEDs are driven by a floating buffer, just like the FTDI chip...
    The LEDs are probably not steady on, but toggling randomly... This is what messes up the FTDI chip and the loading process, I think.
    So, LEDs off may mean that the pins steady...

    I wonder if putting the QS on anti-static plastic would be another way to solve the loading issue...
  • simonlsimonl Posts: 866
    edited 2012-06-24 08:18
    Beau Schwabe (Parallax) wrote: »
    simonl,

    Just out of curiosity, what Rev letter are your QuickStart boards?
    @Beau: They're both Rev A (BTW: Does that mean they've only got 32K EEPROM? How would I find out?)
    Rayman wrote: »
    LEDs on could be related to the loading issue... The LEDs are driven by a floating buffer, just like the FTDI chip...
    The LEDs are probably not steady on, but toggling randomly... This is what messes up the FTDI chip and the loading process, I think.
    So, LEDs off may mean that the pins steady...

    I wonder if putting the QS on anti-static plastic would be another way to solve the loading issue...
    @Rayman: Yup - they're toggling fast - I just viewed the pins using ViewPort and they're all over the place.

    Placing on anti-static plastic also stops the issue (maybe that's why they got off when resting on my laptop too?)
  • cavelambcavelamb Posts: 720
    edited 2012-06-24 10:00
    Four little tiny stick on footies on the bottom of the board will absolve all sins.

    Conductive surfaces under the boards, even high impedance surfaces,
    are shorting pins together causing all manner of unproductive issues.
  • Duane DegnDuane Degn Posts: 10,588
    edited 2012-06-24 10:53
    simonl wrote: »
    (BTW: Does that mean they've only got 32K EEPROM? How would I find out?)

    Post #24 here has a program attached that will tell you the size of your EEPROM.

    It will likely write to your EEPROM twice. Once to place test data in the EEPROM and a second time to restore the original value of the EEPROM. You don't have to load the program to EEPROM for it to work. IIRC it only gives you two seconds to get a terminal window open, so it might be easier to use if you do load it to EEPROM and then reset the Prop if you miss the message at the beginning of the program telling you the size of the EEPROM.

    The part of the program that tells you the size of the EEPROM works fine but the rest of the program is very buggy.
  • varnonvarnon Posts: 184
    edited 2012-06-24 13:41
    Is REV B any different aside from the EEPROM?
    I had a REV A a while back and I really didn't like some of the finickiness of the touch pads and leds. I never had a problem loading a program though.
    With the gadjet gangster USB module gone, I think I'm going to have to start recommending quickstarts to students, and I'm kind of nervous about that.
  • cavelambcavelamb Posts: 720
    edited 2012-06-27 11:02
    I have a Rev A QuickStart nd have no qualm about the touchpads at all.
    Once I got the driver right it has worked perfectly,

    The LED thing is a NON-issue.

    Would you fondle your VGA video card while it is running?

    Like the doctor sail, "Don't DO that!)
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