Recent Posts

31

Test Equipment / Re: FNIRSI-1013D "100MHz" tablet oscilloscope

« Last post by Atlan on Today at 04:36:29 am »

Set 7.5V on both channels, (On the measured CH1 and CH2 values Vpp, Vmax Vmin Vavg) connect DC voltage, press autoset (OLD version). Check the AVG value and write it here. Open the channel menu, highlight AC and then back to DC (don't leave the channel menu). Exit the channel menu, and check the AVG value again. Make video.

But it does not meet the conditions, written above.

32

Metrology / Re: Digitec United Systems Corporation 262B Multimeter Repair

« Last post by emanarias on Today at 04:36:24 am »

The ICs marked 996079 are Fairchild 960 decimal decoder and driver.  Similar to, but a different pinout from, a 74141

995879 are Fairchild 958 BCD Decade Counter with Reset, comparable in function to a CD4510

I have the manual to this meter, and can scan it if you would like.

33

Microcontrollers / Re: $0.11 PY32F002A: Cortex-M0+ MCU, actually a PY32F030! 32/4KB, 48MHz, PLL, DMA...

« Last post by John_doe on Today at 04:35:24 am »

The chip is gone if you reassign both SWC/SWD and NRST.
If you have SWC/SWD reassigned, but NRST is still available, you can still flash the chip if you pull NRST low (which forces the SWC/SWD pins to get reassigned to defaults).

Thanks for the useful tip! I tried it, that is, pinMode() for both the SWD and SWC pins and indeed couldn't connect to the chip anymore. Holding NRST low (and releasing it after the command "reset halt") worked like a charm!

Thanks for the write up. I was excited about openocd for the PY32.... but there's (still) no source and no linux version. Ah well.

Wait, so the PY32 support of openOCD is built into the executable? I didn't know that... I thought that if you download the official Linux version and add the *.cfg files to it from the gitee archive it'll work.

Also may be worth noting: beyond openocd and pyocd, there's also probe-rs which supports the py32.

Thanks, right now I got myself busy with something else but when I'll return to the PY32F002A project I'll be sure to try probe-rs.

34

Programming / Ticketing seat allocation problem

« Last post by cfbsoftware on Today at 04:32:25 am »

My partner and i recently attempted to purchase two tickets to a show but the ticket booking software would not allow me to select my preferred seats (N9 and N10 in the attached seating plan)

because that would have left one isolated seat (N11).

In my opinion, while I can accept that it might be desirable to minimise the creation of multiple isolated seats in a row, the application of this rule in this particular scenario is not sensible. It leads to the following consequences:

The seats in row N in the centre section can only be sold in the following circumstances:

1.   A single person can book seat N9 or N11 (but not N10). Then two people like ourselves would be able to book the remaining 2.
2.   A single person can book seat N9 or N11, but then another single person could not book one of the remaining two seats.
3.   Three people can book seats N9, N10 and N11 if they buy them at the same time.

Similarly for rows O and P.

Worse still, nobody can buy eight tickets in row R as that would also leave one isolated seat

I suspect that the requirements that were given to the programmer were too simplistic. Given the following definitions:

• nIsolatedSeats     = the number of empty seats in a row that are not next to an empty seat
• nOccupiedSeats   = the number of seats in a row that are not empty
• nRequestedSeats = the number of adjacent seats requested in the current booking. Can't be greater than the number of adjacent empty seats.
• nEmptySeats       = nOccupiedSeats - nRequestedSeats = the number of empty seats remaining if the current booking is confirmed

The current algorithm appears to be something like:

Code: [Select]

AllocateSeats(nRequestedSeats)
if (nIsolatedSeats > 0) then RejectBooking else ConfirmBooking
My preferred solution that would avoid the questionable situations described above would be:

Code: [Select]

AllocateSeats(nRequestedSeats)
if (nEmptySeats > 1) and (nIsolatedSeats > 0) then RejectBooking else ConfirmBooking

Am I on the right track?

35

Repair / Re: Motherboard has no power - Clevo W650SC

« Last post by amyk on Today at 04:27:26 am »

Apply power via VIN, since anywhere else could risk backfeeding and damage (there are often "discharge FETs" used to pull rails to ground quickly if the power sequencing determines they shouldn't be on yet.)

36

Beginners / Re: Mystery relic Microchip SOT style chip identify please? Looked everywhere

« Last post by amyk on Today at 04:25:01 am »

Not Microchip, but Mitsumi.

PST600DM in MMP-3A package.

37

Beginners / Re: 72C5 - What Is This?

« Last post by floobydust on Today at 04:20:27 am »

Possibly Panjit BAT721C SMD marking code "72C"  dual Schottky diode.

38

Microcontrollers / Re: A couple questions about Milk-V Duo boards

« Last post by brucehoult on Today at 04:18:18 am »

I think you have to choose one or the other at boot time, but I don't know.

Also see:

https://github.com/orangecms/sg_boot "loader for CVItek/Sophgo SoCs (CV1800B, SG200x)"

He said today initial stuff is working and asked for collaborators.

https://t.me/riscv/1/20904

https://t.me/riscv/1/20913

39

Programming / Re: Linux Dependency Black Hole

« Last post by tatel on Today at 04:17:04 am »

If you don't want to get into dependency hell, just stick to apt and what is in the repositories for the release you installed. Package maintainers did that work for you. To make a package for Debian implies you have full knowledge about all the Debian policies, etc, and to learn it means a lot of work.

I also think things are getting worse. The reason are all those pesky new/better/wonderful ways to install software... that are full of shit. They don't want to learn how to create debian packages, or think they will make some money going that way, or fame/glory/whatever, so they have to invent the wheel again and again. But, while apt is almost the perfect wheel, those new wheels, well, not so much.

AppImage can work. I don't like it however. Docker could be useful if you have servers and want/need to migrate not just the software, but also the contents, from one server to another. What I can't swallow is pip. Use pip to install any python thing, and odds are things will be messed up sooner rather than later, because you have now python things installed, unknown to apt. Pip would like to be half the good apt is. And you'll probably will forget you installed that thing with pip. Then a rough ride will begin.

tar.gz packages? To me, that means source code to be built. If you do so, you'll need to learn previously about the dependencies, and build that dependencies first. And the dependencies of the dependencies. And so on an on... until you have built all what's needed. All should go into a separate partition. There used to be a /local directory just for that partition to be mounted there.  That way you can have different versions of libraries, etc, needed to do the work, and those binaries can be easily preserved if you want to upgrade the rest of the system. I used to do that only for versions of software with new features/fixes that I needed, and I get it back to be installed with apt as soon as the corresponding debian package for "stable" is released.

But, often, the main reason is just user ignorance and unwillingness to read any documentation. Debian has quite good guides, and anyone that did read about the sources.list file, would know that metrologist, in that other thread, is getting messages about hits from two different repositories, one of them for bookworm, the other one for jessie. So, no wonder he got a dependency hell. He just messed things, first, choosing to do an upgrade when the easiest way, not having anything functional on that system, would have been to go for a clean install. Then he modified /etc/apt/sources.list without knowing what he was doing (because he couldn't be bothered to read the guide). Then he complains "Linux sucks". LOL.

Easiest solution: clean install with just the defaults. After that, use just APT to install any packages. If some software couldn't be installed with APT, it just means that software isn't mature enough, and it should be avoided like the plague, until you know what you are doing.

Edit: if you are going to do a Debian install downloading the packages from Internet, just use an ethernet cable. Wifi won't work... because the firmware for the wifi hardware isn't free. You'll have to install that firmware with apt after install is done. It's just the Debian way, and Canonical profiteered from that greatly. Again, anyone that did read the guide would know it... he would even know that an image including non-free firmware, with kernel modules for wifi hardware, is also available, but very few people seems to be willing to read anything nowadays

40

Beginners / Re: 555 driver and Transformer questions

« Last post by Andy Chee on Today at 04:14:12 am »

Transformers do have a hard limit at the lower end, going below will result in core saturation.

The upper limit is much softer and won’t damage the transformer. Basically you hit the transformer’s resonant frequency peak, then the response tails off like a low pass filter.

Ideal waveform is 50% duty cycle. This ensures there’s no net DC that will contribute to core saturation.