Recent Posts

1

Other Equipment & Products / The COMPLETE Octopus (We all need a chuckle these days)

« Last post by watchmaker on Today at 11:12:04 pm »

Here is my final (?) Thai Curve Tracer with Octopus.  It is now fully self-contained.

Still a bench toy, but it is something to talk about.

The two channel scope was $25 on Ali. Could not resist.  It even has cursors and measurements!

2

Computers / Re: Australian Government Invests $1BN on Aussie Quantum Computing Startup

« Last post by coppice on Today at 11:09:26 pm »

... Can they massively reduce the noise, and get some serious entanglement? ...

That is their claimed edge - using an error-correcting fault-tolerant approach.

https://www.nature.com/articles/s41467-023-36493-1
https://arxiv.org/abs/2211.15465

With the massive noise they have now, they do so much error correction the final speed is pathetic. That's why reducing it is key to achieving a useful result.

3

Microcontrollers / Re: Can't disable alarms on DS3231 RTC module

« Last post by Peabody on Today at 11:09:00 pm »

Starting with #if 0.

`#if 0` is disabled code, the `#else` code following is used instead.

Now, the rest of your comment... ahhh... yeah, I suspect that is a bug indeed. I guess I forgot the alarms don't check month (probably should have named the define ..._DOM instead of ..._DATE).

Funny nobody has ever reported it in however many years.  Probably nobody checks for alarms if they are not setting alarms I suppose.

Anyway, long and short, you can't disable the alarm in the register.  Maybe if you set an invalid Day of Month or Hour it might work.  I don't have one around to test with now.

I have several to test with.  I guess the advantage of Feb 31 is that it has no value that is illegal per se, only invalid in combination.  Well, my guess is that in the alarm fields illegal values won't be modified.  I'll try to test that later today.  But if that's true, then you could set the alarm seconds or minutes value to 61, and a match would never happen, so the flag bits wouldn't be set.

But you know, I've used these RTCs for years, and don't think I've ever tested the alarm flag bits.  I've cleared them, but never tested them.  If I'm using alarm interrupts, then INT/SQW will be low if there's been an alarm.  So I don't see why would you need to see if the flags have been set.

4

FPGA / Re: Help on translate schematics to Verilog.

« Last post by caius on Today at 11:00:52 pm »

Thaks for replies to everyone, I was able to improvedesign.But now I'm facing a timing issue, the FPGA does not like the external clock signal input very much.I had to use an external 3-state  buffer (74LS367) to fix this issue but it's not a convenient solution to add another IC to the design.How can I achieve the same result with Verilog?Thanks in advance.

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Microcontrollers / Re: Can't disable alarms on DS3231 RTC module

« Last post by sleemanj on Today at 10:56:49 pm »

Starting with #if 0.

`#if 0` is disabled code, the `#else` code following is used instead.

Now, the rest of your comment... ahhh... yeah, I suspect that is a bug indeed. I guess I forgot the alarms don't check month (probably should have named the define ..._DOM instead of ..._DATE).

Funny nobody has ever reported it in however many years.  Probably nobody checks for alarms if they are not setting alarms I suppose.

Anyway, long and short, you can't disable the alarm in the register.  Maybe if you set an invalid Day of Month or Hour it might work.  I don't have one around to test with now.

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General Technical Chat / Re: H5N1 bird flu and how we're risking another global pandemic

« Last post by NiHaoMike on Today at 10:51:16 pm »

According to the WHO there is no direct threat from H5N1 to turn into a pandemic because there is no spread from human to human.

Not yet, at least. But it spreading to factory farms is especially problematic as it gives the virus a nearly ideal place to grow and a lot more tries to spread to humans. And the fact that it made the (according to scientists) unlikely move to spread to cows indicates it already mutated in a way we don't really understand yet.

https://www.who.int/news-room/fact-sheets/detail/influenza-(avian-and-other-zoonotic)

It looks like H5N1 has been around since 1997. That is almost 30 years already. You can't rule out anything for 100% but it is more likely a different influenza strain which affects humans is going to cause the next pandemic.

Evidence suggests it's already spreading to humans, just not very well at it yet. To assume it will stay like that forever is tempting fate.
https://www.npr.org/sections/health-shots/2024/05/02/1248538298/the-u-s-may-be-missing-human-cases-of-bird-flu-scientists-say

"We know that some of the workers sought medical care for influenza-like illness and conjunctivitis at the same time the H5N1 was ravaging the dairy farms," says Gray, an infectious disease epidemiologist at the University of Texas Medical Branch in Galveston.

"I don't have a way to measure that, but it seems biologically quite plausible that they too, are suffering from the virus," he says.

Gray has spent decades studying respiratory infections in people who work with animals, including dairy cattle. He points out that "clustering of flu-like illness and conjunctivitis" has been documented with previous outbreaks involving bird flu strains that are lethal for poultry like this current one.

...

What concerns him most is the possibility the outbreak could wind up at another kind of farm.

"We know when it hits the poultry farms because the birds die, but the pigs may or may not manifest severe illness," he says, "The virus can just churn, make many copies of itself and the probability of spilling over to those workers is much greater."

The lax regulation of factory farms is the biggest issue, that they could easily be already brewing disease with no obvious signs until it's too late.

7

Microcontrollers / Re: Memory model for Microcontrollers

« Last post by MK14 on Today at 10:48:22 pm »

If the questionable post generates good responses, isn't that what a forum is supposed to be about? Does it really matter what started it if there is proper engagement between posters, and people learn something they otherwise might not?

I still don't like the idea, of possibly poorly written questions and/or bots and/or trolling.  Creating the thread, in the first place.

But you are right.  It can in some cases, lead to rather interesting and education threads, as a result.

8

Test Equipment / Re: Rigol DG800 Combining waveform with arbitrary waveform

« Last post by thm_w on Today at 10:45:48 pm »

As mentioned in the manual:
- Tap the Channel desired in the bottom left of the screen
- Select CombineSet to On
- Choose your waveform to combine with, settings desired, etc.
- This function is only valid for the basic waveforms.

If you want to choose Arb, choose that as the main waveform and then combine it with something else. I don't know if you can do Arb with Arb, I guess if you combine CH1 and CH2 then thats the only option?

https://beyondmeasure.rigoltech.com/acton/attachment/1579/f-08a5/0/-/-/-/-/DG800_UserGuide_EN.pdf

9

Beginners / Re: Very long trace left unconnected at one end... is it bad?

« Last post by radiolistener on Today at 10:43:14 pm »

But you're speaking about signal speed, though? my signal speed is very very low, it's below 10kHz. So my only concern is more regarding the signal edges, hence looking at the rise/fall time.

the shape of signal edges is what it is. More sharp and clean edge requires more high frequency bandwidth.
For example, if you're needs 10 kHz signal with 1 ns rise time, your transmission line needs more than 350 MHz bandwidth and it will be very sensitive to a proper termination.

So it all depends on your specification for "should be fine"... 

10

Beginners / Re: Very long trace left unconnected at one end... is it bad?

« Last post by T3sl4co1l on Today at 10:38:59 pm »

I'd still have to see where connectors and grounding and etc. is going on inside there, but 99.5% sure it's absolutely, positively no issue whatsoever.

Assuming that means FCC Part 15 compliance.  Or maybe even Part 18, even easier?

Ok interesting, thanks for the reply But you're speaking about signal speed, though? my signal speed is very very low, it's below 10kHz. So my only concern is more regarding the signal edges, hence looking at the rise/fall time.

Nonono-- your clock or bit rate might be 10kHz, the transition rate is on the order of 5ns from the MCU (as low as fractional ns for higher speed MCUs, up to maybe 20-30ns for old or slower ones, or slew-rate-limited settings), and probably a fall time of 10ns from the BJT.  That means harmonics all the way up to corresponding frequency scales, i.e. 50MHz.  Maybe not much, at the low rep rate, but you're also talking an electrically-short antenna so it has its own gain proportional to frequency characteristic that balances it out, and you get blips from it.

The kicker is:
1. Trace in PCB is poorly coupled to free space -- this is already enough to pass, e.g. on-board UART signals at 3.3/5V rarely if ever cause trouble;
2. Excessive source termination resistor means the leading edge is attenuated significantly to begin with (i.e. about 20dB);
3. Enclosure, assuming it's at least moderately well grounded to the board, and connectors aren't spreading around common-mode noise somehow coupled to the trace in question (but, coupling has been said to be very low, so that seems impossible), can easily knock that down another, say, anything from 20dB to over 100.

"Well grounded", at these edge rates, might be as simple as a single mounting screw; a great connection isn't really necessary.  Well, assuming the enclosure and board aren't massive or anything, but like palm sized.

More likely all the other connectors emit exponentially more noise, but you asked specifically with respect to one trace, and, it's one of the relatively rare cases, an EMC problem sufficiently well specified and constrained, that a more or less direct answer can be given.

Tim