Propeller NANO

just got in and assembled my new boards. I was modifying the prop mini but this just seamed easier. I use them to control 1/87 scale RC cars and trains. i have access to 27 pins on the back and i added the 10k resistor so i can access the eeprom from my program.

Comments

  • Wow, that sure is a tiny board. Good work.
  • I do not see any caps?

    You need by pass caps on all power lines if the P1 or you will kill the PLL soon.

    Mike
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  • Hi Mike, what size caps would you suggest? i have been running the prop, trasceiver, two motors and some lights off a 100mah lipo and so far so good, but 30 chips for under $5 and 15 day shipping i wouldnt mind editing my file and reordering just to be safe.
  • Nice. I second the bypass caps suggestion, but have had 3 different very simply Prop setups run for up to 3 years without them, so how you use the prop plays greatly into how soon the PLL will get killed. Lack of bypass caps does not directly correlate to infant mortality of the PLL.

    Have any pictures of example installs? Would love to see them.

    You could get the board down even smaller if you used a QFN package, although much more difficult to place without proper equipment. You can pack a lot of stuff in a 1.1x1.4 space with a QFN. What are your size limits for the 1/87 scale "enclosures"?
  • AwesomeCronkAwesomeCronk Posts: 693
    edited 2019-07-16 - 22:28:43
    WBA, could you pass me the microscope? I want to see what bnikkel made!

    I have 0.1uf caps set up for my VIPMC(Virtually Infinite Propeller Modular Computer).
    Windows 10 Home:
    Propeller Tool 1.3.2, BASIC Stamp Editor 2.5.4, Javelin Stamp IDE x.x.x, Arduino IDE, PST
    Hardware:
    BASIC Stamp Board of Education, Propeller Board of Education, Propeller Project Board, Propeller Mini
  • You can get away without caps if the Prop is running slow or only a cog or two are being used etc. However ALL digital electronics require bypass caps due to the glitches that are caused on the supply line when logic elements switch. The fastest they switch and the more that switch, the more noise you will get on the supply which can very well cause your Prop to glitch and crash. I guess that means in this case that a software crash will result in a physical crash of your RC model. But bypass caps are EE101, anyone building any kind of digital logic should already know this.

    However I remember working on a big project years ago where a "pro team" came in and wanted to do things bigger and better. With their grand plans they designed this rather complicated whiz-bang board and couldn't understand why it wouldn't work. Glancing over their shoulders I asserted myself by connecting the scope part of the analyzer to the supply rails where there was a wall of noise and huge transients, well over a volt. There's your problem I said, what do you expect when you don't use bypass caps. The "qualified pro" hardware engineer replied "So? What's the problem with that?" a$%%!$&#*(!#! good grief! I walked away dumbfounded by his reply.

    BTW, why use such a monstrous crystal and diode? Besides, the Prop's crystal input is like a really sensitive receiver and long leads here will only pick up noise that disrupts the whole chip.
    Just use a tiny 0603 diode and 3225 oscillator or similar. Have a look at this older board of mine that was designed to mate to my LAN module. You can see the oscillator and bypass caps.

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  • Bypass caps:
    Just experienced this very problem; stuck a bunch of PICs on Perma-Proto boards and none would fire up. Installed 0.1uf bypass caps and they all burst in to life.
    Failure is not an option...it's bundled with the software.
  • the diode is there to give me just enough voltage drop to directly connect a 1s lipo to the prop, the crystal i pulled from a propeller project board. i had started a discussion about smd crystals trying to get a part # for one that would work but it ended up getting confusing so thats what i ended up with. here is a pic of the remote i made as of now it can store 40 vehicles, control 8 servos and 16 0n/off functions. the touch screen lets you adjust all the names of vehicles and settings.
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  • Peter JakackiPeter Jakacki Posts: 8,511
    edited 2019-07-17 - 14:16:33
    Good work, looks good. Just please don't forget the caps (and direct electrically short connections too).

    I realize that you are using the diode for a rough voltage drop but an smd diode on the board would take up a lot less space but it would just be better to have an LDO regulator in that case in a small SOT23 pack. Don't bother trying to get really small 5MHz crystals as it is far easier to get oscillators for the same price these days. Here is a 5MHz 15ppm 3.2x2.5mm TXO for around $1 though there are smaller options again.

    There are plenty of parts for the LDO but I just used a dual reg in a tiny SOT26-6 recently on my P2D2 designs. Just use one half if you like. They are only around 35cents. But you must use proper decoupling on the regulators and the Prop. Normally 100nF ceramic MLCC caps and 0603 are easy to handle.

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  • jmgjmg Posts: 13,778
    bnikkel wrote: »
    .. the crystal i pulled from a propeller project board. i had started a discussion about smd crystals trying to get a part # for one that would work but it ended up getting confusing so thats what i ended up with. ...

    At 5MHz Xtal elements tend to be large.
    Digikey do stock AB308-5.000MHZ 5MHz ±30ppm Crystal 16pF 150 Ohms Cylindrical Can, Radial 3.00mm x 8.00mm, so you would fold that over the TQFP package

    If you want the simplicity of a small SMD Xtal, you could look at a newer 'better spec' Ceramic Resonator, like CSTNR5M00GH5C000R0 Ceramic Resonator 5MHz ±0.07% (Tol) ±0.13% (Stability) 39pF 60 Ohm
    Automotive - 40°C~125°C 3-Pin 4.5x2mm ~ 33c/100

    Oscillators can come quite small, like
    DSC6001HI1A-005.0000T MEMS OSC XO 5.0000MHZ $0.8652/100 1.71V ~ 3.63V ±50ppm -40°C ~ 85°C 1.3mA (Typ) (1.60mm x 1.20mm)

    and Peter links a quite good ±15ppm model 3.2x2.5mm above.
  • i have modified my pcb file and have a 10k resistors on the scl and sda of the eeprom and a 0805 size cap trace on the vss/vdd lines as close to the prop as i could get it, anything else i should think about? and thanks for all the help everyone, really appreciate it.
  • Peter JakackiPeter Jakacki Posts: 8,511
    edited 2019-07-23 - 23:45:59
    Best to show us the layout because "close" might mean physically close but electrically remote. You really need to put an SMD crystal or oscillator in there or at the very least 2 small pads for a cylindrical crystal, as those HC49s are unnecessary monsters. Don't be afraid to use 6MHz crystals since they will work fine and it is a lot easier to get smaller crystals at that frequency. What about an LDO regulator in place of your diode? I even use MC1702s in SOT-89 packs which are easy to hand solder.

    BTW, for pullups I like to use 4 way resistor arrays since they are easy to handle being around a 1206 size but pack 4 resistors.

    Which pcb software are you using? Zip the files as well as post the images of the layout (even screenshots).

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  • here is the new design, from left to right cap,R1,R2.
    the second pic is how i was modifying the prop mini, i had a 22uf cap on +/- just as a voltage buffer for when other things turned on but that must have also acted as a bypass cap?
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