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Prop chips from other sources? — Parallax Forums

Prop chips from other sources?

coffeelovecoffeelove Posts: 14
edited 2011-08-23 11:03 in General Discussion
did i screw myself over by getting the propeller chips from digikey? no matter which programming method i use ( serial transistor or prop-plug ) i am unable to find the chip on any com port. :frown:

i've setup my breadboard using the schematic in the datasheet, but with no such luck.

thanks in advance for any suggestions / ideas.

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2011-08-15 23:10
    It's the same Propeller chip no matter who you buy it from. The published serial transistor interface works as well as the PropPlug and the schematic in the datasheet works. There's something in what you're not telling us that's probably the reason it's not working for you. Note that you don't need an EEPROM or a crystal to have the Propeller recognized by the Propeller Tool, just the Propeller chip itself and the programming interface.

    Best thing to do is to come up with a schematic of exactly what you have on your breadboard (not what you think you have) and how it's connected to the PC and your power source (3.3V regulated) and post it. If you're running the Prop off batteries, make sure the batteries are fresh and that your regulator is producing what's expected.
  • coffeelovecoffeelove Posts: 14
    edited 2011-08-16 07:21
    Thank you for the info. in the attached schematic, just pretend that the 40pin JP1 is the propeller with standard numbering from pin 1 around the outside. battery is fresh, and VOUT from LM317 is 3V3.

    prop_prog.png


    happen to have an eagle library for the propeller?

    edit: geh.. that 230R on the eeprom is actually a 10K on my board.
    prop_prog.png
    823 x 448 - 8K
  • LeonLeon Posts: 7,620
    edited 2011-08-16 07:39
    You need a capacitor or two on the LM317 (see the data sheet) and decoupling capacitors on the Propeller.
  • Mike GreenMike Green Posts: 23,101
    edited 2011-08-16 07:39
    I don't know what you're trying to do with the regulator, but it can't work properly as drawn. Have another look at your schematic and compare to the examples in the LM317 datasheet or pretty much any examples on the internet.

    The first thing that jumped out at me was the complete lack of capacitors. The LM317 can theoretically work without input or output capacitors, but, in practice, you need at least a 0.1uF input capacitor and a 1uF or higher output capacitor. In addition, the Propeller has to have, at a minimum, a 0.1uF bypass capacitor across the Vss/Vdd pins on each side of the package, as close as possible to the pins.
  • coffeelovecoffeelove Posts: 14
    edited 2011-08-16 08:01
    thank you again. i'll be adding those today & keep you updated.

    like i stated, i went directly from the schematic in the datasheet for setting this up. please forgive the utter newbness of the schematic.
  • ctwardellctwardell Posts: 1,716
    edited 2011-08-16 08:03
    The regulator circuit is wrong. Disconnect Vcc and Gnd from the Prop and EEPROM and work on getting the regulator working BEFORE connecting it back to the other chips.

    Check the datasheet for the LM317:

    http://www.national.com/ds/LM/LM117.pdf

    Look at where you have pin 1 (adj) of the regulator, it should be at the junction of R4 and R5.

    Look at where you have the GND pins of the Prop and Propclip, you have them at the junction of R4 and R5 instead of ground.

    Plus you need the caps that others have suggested.

    C.W.
  • coffeelovecoffeelove Posts: 14
    edited 2011-08-16 09:19
    Ok, so all the way back to the basics.. i've redone the 317 according to datasheet including caps, added in the caps to the prop, and removed everything that was listed as optional ( eeprom & xtal ).still no luck. see schematic attached.

    prop_prog.jpg


    battery output is still around 8v5 while 317 is putting out 3v1...
    prop_prog.jpg
    1024 x 557 - 31K
  • Mike GreenMike Green Posts: 23,101
    edited 2011-08-16 09:33
    The 10uF capacitors on the Prop's Vss/Vdd pins are not adequate (more isn't better). You really need ceramic 0.1uF capacitors. The reason is that the Propeller's system clock runs anywhere from 12MHz to 20MHz while it's talking to the Propeller Tool on the PC and 80MHz or above when it's running under control of the crystal. There are switching transients on the Vss/Vdd pins on the order of 50ns to as little as 10ns and the 0.1uF capacitors help provide the current for those transients. The 10uF capacitors can't respond fast enough.

    The Propeller Education Kit lab tutorials are good references for what you're trying to do.
  • Beau SchwabeBeau Schwabe Posts: 6,568
    edited 2011-08-16 09:45
    coffeelove,

    Ignoring the erroneous regulator connections, if the rest of your schematic is true to what you have, your VSS, BOEn, RESn, and VDD are all shifted one place to the right from where they should be.
    Propeller.JPG
    768 x 456 - 70K
  • RDL2004RDL2004 Posts: 2,554
    edited 2011-08-16 11:38
    Just because it might be helpful, a drawing I made.
    Everything you really need to know about LM117/317 in one picture.
    (Well, I probably should add the equation for setting the output voltage)
    If anybody sees any errors, please let me know so I can fix.
    LM117317.jpg
    640 x 448 - 160K
  • davejamesdavejames Posts: 4,047
    edited 2011-08-16 12:22
    RDL2004 wrote: »
    If anybody sees any errors, please let me know so I can fix.

    RD - the values for R1 on your diagrams create the impression that 240 Ohms is for one model of the regulator and 120 Ohms is for the other.

    R1 is used in conjunction with the x17's reference volatge (typ. 1.25V for both the 117 and 317) to set the programming current that will be used (in conjunction with R2) to set the output voltage.

    So, one could use 120 or 240 Ohms on either x17 regulator.

    If the datasheet of the National Semi LM117 is used as the source, page 9 delves into this in detail.
  • RDL2004RDL2004 Posts: 2,554
    edited 2011-08-16 14:25
    It is my understanding that this is a better way to do it. The way it was explained to me is that not all LM317s will work correctly with 240 ohms, they may need more than the "typical" adjustment pin current (even though they are still in spec). If this is the case the output voltage will rise with no load. The LM117 is a better quality part and normally doesn't have this problem. National almost always shows an LM117 with the 240 ohm, though they are pretty inconsistent about this in general.
  • Daniel HarrisDaniel Harris Posts: 207
    edited 2011-08-16 14:51
    Coffeelove,

    Beau's right. Those need to be re-wired. Also, I have minor issue with your ground rail. Particularly, to reach Ground (Vss), the Propeller has to go through that 470 ohm resistor (R5). I haven't messed with adjustable regulators, but that could be an issue. If you re-wire those pins and it still doesnt work, try wiring the Propeller up in such a way such that Ground is run straight to the negative terminal on your battery/power supply.

    Thanks,
    Daniel
  • davejamesdavejames Posts: 4,047
    edited 2011-08-16 17:51
    RDL2004 wrote: »
    If this is the case the output voltage will rise with no load.

    Maybe that's why the datasheet states a minimum load current for the x17.

    Just guessin'...
  • coffeelovecoffeelove Posts: 14
    edited 2011-08-16 23:49
    ok.. ignore the retarded schematics. i can't draw for Smile.

    i've followed every single suggestion on here with a different propChip each time in place of the original, so if i've fried all 5 of em. damn...

    my big question from the original statement is this "did i screw myself over by getting the propeller chips from digikey?", meaning: do the chips from a non-parallax source still have the bootcode in ROM, or do i need to find a high-voltage-programmer for these confounding chips? an example would be the "AVRDragon" for atmel chips.

    if the answer is yes, kindly point me in the direction to find it, else i have NFI what i'm doing wrong anymore.
  • LeonLeon Posts: 7,620
    edited 2011-08-17 00:09
    There is no equivalent of AVR high-voltage programming for the Propeller, and there is no boot code in ROM. You just need to connect the chip properly, with the correct voltage supply, and it should work. I've only had a Propeller chip fail on me once, and that was because I had a tiny short on my home-made PCB which put 12V across it.
  • coffeelovecoffeelove Posts: 14
    edited 2011-08-17 00:41
    Thank you.

    I'll redo my board again n see where I've gone so horribly wrong that its not working.
  • Jorge PJorge P Posts: 385
    edited 2011-08-17 03:09
    @coffeelove
    Before plugging in your prop to PC, did you install the FTDI drivers, if not download and install them from http://www.parallax.com/tabid/530/Default.aspx . As a general rule of thumb, never plugin new hardware to your PC until after you install the drivers. Make sure the propclip/plug is not connect to the PC while installing the drivers or you will need to restart your PC.

    Double check your board with the PE Kit manual page 31 to 38... 38 shows what Mike Green was talking about with the Caps. Also make sure your propclip is not plugged in upside down, I did that the first time I connected it. If you wire your board exactly like the PE Kit diagrams, the propPLUGs Paralax Logo should be facing down, I am not sure if it is the same with the propCLIP....
  • Heater.Heater. Posts: 21,230
    edited 2011-08-17 03:12
    coffelove,

    I would be very surprised if you got 5 dud chips from any reputable supplier. The Propeller proves to be quite a rugged chip and one of the easiest MCUs to get going. To be clear, it does have a bootloader but it is in mask ROM meaning it is built in when the chip is made so they all have it out of the factory.

    Basically, to get a prop running you don't need the crystal, it will run from it's internal slow clock without. You don't need the EEPROM, the Prop Tool can detect it and load it's RAM without one.
    So all you need is:
    Be sure your power supply voltage is correct before connecting to Prop.
    Be sure the ground pins are connected to together at the chip.
    Be sure the power pins are connected together at the chip.
    A sprinkling of smoothing capacitors and decoupling capacitors, the later should as close to the Prop as possible, see many typical circuits for details.
    Ground pins connected to ground.
    Power pins connected to power.
    Take care of BOE pin as per data sheet.
    Connect to your Prop plug.

    The Prop Tool on should now detect your Propeller. Try and down load a simple program.

    Download a simple program to set a pin high, you can see it work with a multimeter or LED and resistor on the pin.

    After that you can add the crystal and add the clock setting statements to your simple program.
    After that you can connect up the EEPROM and try to get your code into there.
    Then the world is yours:)

    That's basically how I got my first DIP Prop running.

    I have not followed all the tribulations of this thread in detail but, sadly, I suspect you have indeed fried the Props. The steps above will find out how badly.

    Don't give up yet!
  • coffeelovecoffeelove Posts: 14
    edited 2011-08-17 10:58
    well, it would appear that i have fried all but one of the chips. :(

    thank you all for your help. after re-reading all your comments and the datasheets over and over, i finally "got" the 317 setup correctly, seems that if you wire it backwards it will still output 3v1 but with odd spikes in current. :innocent: ...

    lesson learned! :thumb:

    and now onto figuring out XBee & NMEA parsing... wish me luck!
  • ctwardellctwardell Posts: 1,716
    edited 2011-08-17 11:13
    Good luck! You may have had a rocky start, but I think you will learn to like the prop.

    C.W.
  • vanmunchvanmunch Posts: 568
    edited 2011-08-23 10:45
    Hello,

    I'm glad you guys were having this discussion, because I just populated my first surface mount board using a QFP last night and I can't detect my prop. I think it's because I don't have any capacitors across the prop's Vss/Vdd. (or one of a 100 other possibilities, but this sounds the most likely)
    Mike Green wrote: »
    The 10uF capacitors on the Prop's Vss/Vdd pins are not adequate (more isn't better). You really need ceramic 0.1uF capacitors. The reason is that the Propeller's system clock runs anywhere from 12MHz to 20MHz while it's talking to the Propeller Tool on the PC and 80MHz or above when it's running under control of the crystal. There are switching transients on the Vss/Vdd pins on the order of 50ns to as little as 10ns and the 0.1uF capacitors help provide the current for those transients. The 10uF capacitors can't respond fast enough.

    The Propeller Education Kit lab tutorials are good references for what you're trying to do.

    I didn't even realize that these capacitors were needed because I had followed and built the PEK following the schematic in the box insert:
    http://www.parallax.com/Portals/0/Downloads/docs/prod/prop/PEKit_40PinBoxInsert-v1.2.pdf

    Are the 0.0uF capacitors something that's needed with the QFP but not the DIP chips? I just figured that I'd ask before I start soldering some 0.1uF capacitors tomorrow. If it still doesn't work I'll bring it to the UPE this weekend and bug anyone form Parallax. ;)
  • RonPRonP Posts: 384
    edited 2011-08-23 10:59
    vanmunch,

    The caps are a suggested PE Platform Circuit Enhancement . This and other info can be found here.:smile:

    Not sure that is the reason you can't detect your Prop.

    -Ron
  • Mike GreenMike Green Posts: 23,101
    edited 2011-08-23 11:03
    The 0.1uF capacitors are really needed for pretty much any digital IC, one for each IC. In the case of the Propeller or other complex chip with multiple power supply pins, one for each pair of supply pins. The fact that you can "get away" without them doesn't mean that they're not necessary. It depends on the amount of power the chip draws, how fast it's capable of switching, how fast it actually switches, the stability of the power source, etc. The basic issue is that wires have some inductance and capacitance. Particularly at higher switching speeds, the power from the power source itself can't reach the chip via the wiring fast enough for the switching that the chip is trying to do. The 0.1uF capacitors provide a local power buffer. In the case of the Propeller, you need more than one capacitor because the wiring on the chip itself is very small and has some significant resistance and capacitance (for the circuits involved). If the power for some rapidly switching portion of the chip has to travel across the chip to get there, there are voltage drops and induced voltages that can throw off other parts of the chip in the process.
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