View Full Version : After Loading, Program Not Running, Sometimes

05-20-2010, 08:07 PM
Problem:· In the last days the the Propeller has not always run a program after seemingly correct program loading.

I have been working through the Propeller Education Kit Labs and have on numerous occasions successfuly loaded and run programs.

-- No wiring changes have been made since·things worked reliabily.

-- Voltage at the Propeller is 3.28 volts.

-- With the Propeller Tool, F7 always identifies the chip on COM8.

-- When the battery is NOT connected, and the Propeller Tool·IS connected to Propeller and to the PC via USB, the power LED no longer dimly glows.· Is this significant?· I believe that the LED used to glow in this setup.

Regardless, after seemingly successful loading of a program from the Propeller Tool·via F10·or via F11,·programs only sometimes "run".

Any suggestions on what might be wrong?

-- George

Oldbitcollector (Jeff)
05-20-2010, 09:24 PM
This is sounding like a loose or broken wire.

Do a check of your wires with a meter and make sure they are in good shape.

Are you using solid core wire or stranded? I've had solid core wire break inside the plastic making it "look" they
it was still connected, but creating the same momentary functionality that you have described.

Let us know how you get along.


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Post Edited (Oldbitcollector) : 5/20/2010 4:30:37 PM GMT

05-20-2010, 10:17 PM
That's an interesting thought.··

The jummpers on the breadboard use solid wire.· It is certainly possible there is an intermittent break in a stripped wire as you suggest.· Or perhaps a short lead into a breadboard socket making intermittent contact.·

In the last hour my programs have been loading and then running without problems.· Fifteen minutes ago I just had my very first "lost Comm 8 contact" message during program loading.· Not sure what caused that.

Thanks for your feedback.· As soon as I see another failure I will check all of the wiring.


05-20-2010, 10:19 PM
Are both supply pins connected and decoupled close to the chip? It's important.

Leon Heller
Amateur radio callsign: G1HSM

05-20-2010, 10:38 PM
Yes, both grounds and +3.3 are connected.· The breadboard is wired according to the instructions in the Propeller Education Kit Lab book, so I ASSUME the decoupling is sufficient.

However, I recently noticed that the chip seems not to be running at 80 MHz but something much slower.· When I comment out...

···· '· _xinfreq = 5_000_000
···· '· _clkmode = xtal1 + pll16x

the programs run (blink LEDs) at an appropriate rate.

More strangeness.

-- George

05-20-2010, 10:41 PM
Do you have two decoupling capacitors close to the chip?

Leon Heller
Amateur radio callsign: G1HSM

Phil Pilgrim (PhiPi)
05-20-2010, 11:26 PM
I just looked at the manual for the PEK, and there are no bypass caps specified or included in the kit -- only filter caps for the regulators. This could well be the problem. George, if you happen to have a couple 0.1uF ceramic caps lying around, try connecting them across Vdd and Vss on both sides of the chip. Be sure to clip the leads as short as possible while still making a good connection.


05-21-2010, 12:49 AM
0.1 uF bypasses installed now on both sides.· Let's see this afternoon if that makes a difference.

Thanks, George

05-21-2010, 09:17 AM
Installing the 0.1 uF bypass capacitors at the Propeller power terminals did make a difference in the success of getting programs to run following download.· HOWEVER, ...

Tonight I swapped out the Propeller, and...

-- Programs load and run fine,
-- Propeller processing speed is correct, and
-- The power indicator glows dimly with the USB Prop programming tool installed and 3.3 volt power off.

I have no idea why the original Propeller module "failed" in such a manner.

Thanks for all of your suggestions.

-- George