Propeller NANO
bnikkel
Posts: 104
in Propeller 1
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.
640 x 1136 - 1M
640 x 1136 - 1M
Comments
You need by pass caps on all power lines if the P1 or you will kill the PLL soon.
Mike
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"?
I have 0.1uf caps set up for my VIPMC(Virtually Infinite Propeller Modular Computer).
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.
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.
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.
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.
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).
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?