This code produces nice 1.5Ms pulses on Pin 9 as I expect. What I did NOT expect was a "phantom" pulse on Pin 10 which is exactly what I'm seeing. I've attached a snapshot from my Oscilloscope showing the issue. Note that I'm running the code above, and I'm clipped into Pin10 on my ZX24r.
I can uncomment the Pin 10 line in the above snippet and then I get a double pulse on Pin10 (and on Pin9 as well). I've shown a shot of that below too.
Any ideas on this? I'm totally stumped. . .could I have a damaged chip somehow?
This shot has pulses running on both pins 9 and 10. Note that you can see the generate pulse on Pin 10 here (where I'm clipped) but you can also see the Pin 9 pulse.
Well, the unconnected pin's (10) signal is not the same frequency as the one getting the pulseout (9). The unconnected pin appears to have 60 hz power line hum.
Hook up a lead to the power supply and see if it matches the signal on pin 10.
Put a big electrolytic cap near the ZX (across the VCC and GND) and also add a couple 0.1uF ceramics in parallel with the electrolytc. Does that reduce the noise on pin 10?
You did not say if the pin you were measuring was connected to anything. If it was floating free I would expect to see what you are getting. Temporarily connect a 10K resistor (or any other similar value) from the pin to ground and see if the phantom signals go away.
Sorry, I should have mentioned that I did hook up a pull-down resistor to the floating pins and still saw the same behavior. The issue is not with the power supply, it's directly related to the other pin, I can change the timing on the "phantom pulse" but adjusting the other pin. VERY strange.
UPDATE: As of this morning the entire chip has died. I left it running a series of tasks all night last night, and this morning it is totally DOA. IT gets extremely hot and pulls a lot of current so I suspect something is shorted out internally???
Don,
Is there any way to repair one of these? I hate to drop $50 for another one, particularly when I'm not really sure why this one decided to go belly up. I've tested/checked my schematics, used ZX24p processors with no issues. . .and last night the chip actually wasn't even connected to anything at all, I dropped it right into a development board with nothing hooked up, just letting it run several tasks. Quite a mystery from my perspective. . .maybe static zapped it somehow???
everest wrote:it's directly related to the other pin, I can change the timing on the "phantom pulse" but adjusting the other pin. VERY strange.
But I don't think it was directly related! The frequency of the switching on pin 9 was between 72 and 85Hz and the "phantom" signal was 59.7 and 59.8 Hz. That is quite a bit different to me!
It looked to me that they were completely unrelated....
I have only killed AVR CPUs by miswiring them and pulling a lot of curent through a pin, or by having nasty spikes, like inductive spikes hitting the uC.
everest wrote:
UPDATE: As of this morning the entire chip has died. I left it running a series of tasks all night last night, and this morning it is totally DOA.
While the excessive heat issue is certainly something to be concerned about, have you tried an emergency update using the techniques specified in section 9.1.1 of the Language Reference?
Thanks for all the replies, and Don I'll ship out the chip tomorrow. I'd be very interested if you could let me know what the issue was/is, and particularly if it could have possibly been anything I did to the processor.
I have a hard time with my static electricity theory given that my ZX24P took a moderately close proximity lightning strike without batting an eyelash.
So I'm just stumped. Fortunately I've got a few 328n chips with interface boards lying around, plus a spare ZX24p. . .so the fun goes on!