Can't get past 40MHz

photomankc

Setting up a pretty basic board here.· Gadget Gangster BOSS board with EEPROM and Prop with a few LEDs and some PB switches, nothing much else included.· I can run at 40Mhz (5MHz + PLL8x) but any attempt to run at PLL16x results in silence, no program output nor other indication that it is alive.· If I switch back to 40Mhz then all is good again.· I've tried all the caps I have from .1 to 47uf on the crystal side supply lines·and nothing helps.· I have tried using battery power to rule out the wall wart power supply.· I have another board that will run at 80 and when I swap the Propeller from there into this board it also refuses to run at 80 so it's definitely something·about this board.·

I have 100uf electrolytic on Vin and Vout from the 3.3V regulator.· I have .1uf on the left side of the prop and a 4.7uf on the right side.·

Kind of bummed.· I wanted to build this to get it off the breadboard where it seemed unstable.· · I'm not equipped with a scope yet so a multimeter is all I had at hand.· I don't pick up any A/C on the power though.· If there·are any things that I should look at that you know of·I'd love a head's up.··I don't expect any miracles here since I don't·have a schematic to show yet.· I'm kinda wondering if maybe the crystal has issues.

Oh well, it's bedtime.·

HollyMinkowski

I had a project on a solderless breadboard and it was not at all stable with a 6.250 xtal at 16x
but ran ok at lower freqs. When I built it up on an actual circuit board it worked fine.

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- Some mornings I wake up cranky.....but usually I just let him sleep in -

Leon

You have decoupled both the supply pins close to the chip?

Leon

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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle

StefanL38

hello photomankc,

can you post your testcode ?

did you test it with some small blinking program using hardcoded values for waitcnt ?

in the attachment is a little demo-program that starts a cog and blink a LED connected to an IO-pin of your choice

if you insert this as the first command in your code you always see when the prop
finished his bootsequence and starts running and is running as long as you see the LED blink

best regards

Stefan

photomankc

@Stefan - The program you sent operates the same: 40Mhz it runs.· 80Mhz I get nothing except one time I got the LED locked in the on state.

Here was the original test code:

CON
    _xinfreq = 5_000_000                     
    _clkmode = xtal1 + pll16x
 
PUB LedOnOff
    dira[noparse][[/noparse]25] := 1
     
    repeat
        outa[noparse][[/noparse]25] := 1
        waitcnt(clkfreq + cnt)
        outa[noparse][[/noparse]25] := 0
        waitcnt(clkfreq + cnt)

@Leon - Yes I have caps on both sides supply lines.· I started with two 10uf tantalums and no joy at 80,·but after reviewing some other designs I tried .1 ceramic on the left side and 10uf on the right.· It wigged out completely, timing was off by +300%.· Out of desperation I added 47uf electrolytic on the right side and I'm back to it running at 40MHz.

I attached a photo of what I have.

Phil Pilgrim (PhiPi)

Your 4.7uF "bypass" cap is an aluminum electrolytic. It makes an okay filter cap but is ineffective for bypassing. Try paralleling another 0.1uF ceramic cap with it and see if that helps.

-Phil

Leon

I use a 100n ceramic on each pin.

Leon

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Amateur radio callsign: G1HSM
Suzuki SV1000S motorcycle

photomankc

ARRRRRHHHHHH!!!!!!

Found it!··Apparently the BOSS board routes the xtal pin up to the holes next to VDD and VDD doesn't connect outside the pin itself on that side.· What I had was only one pin of the crystal attached and a capacitor loaded on the other end.· Good grief.· It would be nice if the BOSS traces were easier to see.· I only bumped into this by accident when I was checking continuity and slipped to hit the xtal pin instead of the cap.· I would have never found that otherwise.·

SRLM

I thought the crystal was a little close. I like the boss board, but it's pretty intense for me. So I made a color coded guide. The bottom isn't color coded yet, but it does show the traces. It's also available on the GG site.

http://forums.parallax.com/attachment.php?attachmentid=60284

photomankc

Yeah, I had the drawing they sent with it and it appears to either have an error or it's very confusing because·it look as though all the pads on right side are connected to the pins on the right next to them. The drawing you have is much more clear. Anyway, we're cooking with gas now. It's running at 80Mhz just fine now.