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th_in_gs, in SBC UART debug troubleshooting

I suspect your serial converter is expecting a ‘real’ RS232 signal, with its old-school now-weird voltage levels.

Your USB serial adapter is probably using 5V or 3V so-called ‘TTL’ signaling (which in the real world is mostly cross-compatible between 5V and 3V)

Good explanation here: https://www.sparkfun.com/tutorials/215

MaximGun,

Yeah this must be it. Thanks.

PCChipsM922U, in SBC UART debug troubleshooting
@PCChipsM922U@sh.itjust.works avatar

It's probably just the converter... something misconfigured in the drivers or... who knows. Try and see if you get the same garbled data in Windows and Linux (binary check). If they match, it's something hardware wise.

Back in the day, yes, the Chinese USB to Serial/Prallel converters were terrible, no doubt there. But, over the years, they've gotten surprisingly good. In fact, I picked one up a few weeks ago (as you said, about $5), works like charm.

th_in_gs,

I suspect your serial converter is expecting a ‘real’ RS232 signal, with its old-school now-weird voltage levels.

Your USB serial adapter is probably using 5V or 3V so-called ‘TTL’ signaling (which in the real world is mostly cross-compatible between 5V and 3V)

Good explanation here: https://www.sparkfun.com/tutorials/215

sweafa, in Ultra-Fine Multimeter Probes

https://sensepeek.com/ do manufactur those nice PCBite SP10 probes. New improved series: SQ10 probes. They also have 500MHz Oscilloscope probes! They are awesome :D

Then there are those small pincers: https://at.rs-online.com/web/p/klemmprufspitzen/0775704 Or very small pincers: https://www.sks-kontakt.de/de/test-measurement/produkte/produkt?nr=9741011 (digikey lists them as manufacturer Altech Corporation)

Spring-loaded tips: https://www.sks-kontakt.de/de/test-measurement/produkte/produkt?nr=9739951

Eufalconimorph,

The SensePeek PCBite system is really nice. They're the best board holders I've ever used, very stable. Great for testing, and great for soldering. The probes are ridiculously helpful, it's downright easy to probe adjacent pins on a 0.5mm pitch QFP (with some magnification)! All rather expensive, but very, very worth it for the time saved.

Belgdore, in Weird cable with USB A connector with 5 pins

Sounds like you bought a crappy cable. Why not just buy a good one instead of disassembling and replacing stuff?

My guess is that it needs the fifth pin to trick some devices to think that it’s a 3.0 cable instead of a 2.0 with a c connector.

human_no_4815162342,

Type C 2.0 exists and is widespread and that is what I wanted, the issue is that it doesn't work as a 2.0 cable either. I like the liquid silicone exterior and I have a few connectors ready so if I like what's inside I may upgrade it. Otherwise I will recycle it and I already have better cables.

Belgdore,

Hey fair enough. If you are really concerned about what it if you could always reach out to the manufacturer

duckythescientist, in Weird cable with USB A connector with 5 pins

Pics would be helpful

human_no_4815162342,

I am pretty busy this week, I am posting when I have breaks and I don't have it with me. When I'll have the time I will make a post with photos and measurements and I will probably also open it up.

Saigonauticon, in Weird cable with USB A connector with 5 pins

In my experience, if they don't include the conductor in the connector, there will generally not be a wire for it in the cable. So replacing the USB-C connector is probably not going to add any functionality.

I have a stack of USB-A to USB mini/micro cables that are a bit like this. Two conductors, only do charging. So if I replace the connector, there's no wire to connect the D+ / D- lines to. It's quite possible the manufacturer of your cable had some similar or otherwise reduced feature set in mind, and wanted to save 5 cents of copper.

I also have some cursed cables that have normal ports, but only two wires inside the cable (power/ground), or are otherwise out-of-spec in ways that make the data lines mostly fail. These have wasted quite a bit of my time over the years.

human_no_4815162342,

I only need a USB 2.0 cable mostly for charging, I have better cables, I chose this one for the liquid silicone outer layer. Of course if the wires inside are less than four or too thin I won't waste USB connectors (that I already have, I would not order them for this) and I will recycle it.

MegaGoat, in Safety tips when disassembling old electronics?

There is the old thermal paste made of Beryllium oxide. Best not to eat it.

nilclass,

Best not to eat it.

dang... what else to do with the leftovers then?

Saigonauticon,

Grind it into dust, add sand, pour molten non-recyclable plastic into it (e.g. recyclable plastic with too many impurities). Market it as a weighted ballast material e.g. for the base of IKEA lamps.

Saigonauticon, in Safety tips when disassembling old electronics?

Mostly I just work in a well ventilated area. Oh and for sure disconnect power before desoldering anything.

Other than that, I avoid taking apart microwaves (beryllium, high voltage), anything with a CRT (imploding glass, high voltage), and high voltage transformers (transformer oil, high voltage). Also any medical equipment (chemical hazard, radiation hazards, biohazard, high voltage, imploding glass). Oh and no unexploded munitions for reasons that should be obvious (people still salvage these in my country and it sometimes doesn't end well).

I find a hot air rework station+tweezers a much faster way to salvage than jamming a hot iron into boards. Also lets you salvage SMT components, which are most of the better parts these days. For 1970s stuff, it's mostly through-hole, I'd test the parts before trying to reuse them. Capacitors especially. Got to love those big transistors from our side of the Iron Curtain though.

Swiggles, in Safety tips when disassembling old electronics?

Some old electronics use asbestos in heating elements or for shielding. Be careful when dealing with old hair dryers, coffee makers, stoves etc.

I don't see how there could be any in your tape recorder though. It's just what came to my mind when I read the title.

nilclass,

good to know for the future!

hardware26, in [SOLVED] A pull-up resistor increases the low side of a signal, how can I counteract it?

Problem you are having could be

  1. output impedance of the signal generator you use to generate the square wave. When you set it to low, output impedance of the signal generator builds a voltage divider together with the internal pull up, and the device ends up sensing a higher voltage than "low". This is something you can see if you have an oscilloscope, try to hook up a probe to the input and ensure whether you get what you set in the signal generator.
  2. some signal sources have no or limited capacity to drain current. And when you set it to low, this is exactly what it us supposed to do, drain current from the internal pullup.

As you mentioned in another comment, solution is a simple buffer. This could be an opamp, but even a simple nmos transistor should suffice (open drain as you said). But you need yo be careful with current ratings of the transistor, which you can easily calculate by dividing 5V by the pull up resistor. Send a message if you need help.

Before these, I suggest you yo use an oscilloscope or multimeter to measure the voltage when it is supposed to be low, and see that in fact the problem is that voltage at the input doesn't go "low".

lightrush,
@lightrush@lemmy.ca avatar

Thanks for the explanation!

I measured the signal generator alone, not connected to the input. It goes to 4.5V high and 0.001V low. Then I connected it to the input and measured at the input. I got 4.5V high and 1.1V low.

Also I ordered the 74LVC1G07 buffer along with a breakout board which should allow me to hook it up inline and test. I'll report back when I do.

hardware26,

It should do the trick I think. If you are working on electronics a lot, you may consider buying a breadboard and variety of resistors, capacitors and nmos, pros, bjt transistors in bulk for quick fixes instead of waiting for orders to proceed. Have fun

lightrush,
@lightrush@lemmy.ca avatar

It works!

https://lemmy.ca/pictrs/image/70cae57f-710c-4dc5-ba06-204efec4ecf2.jpeg

I just built this monstrosity, tested and the signal is correctly detected by the computer. 👌

Now I just need to wire it properly.

hardware26,

Well done, good to hear

Susan_B_Good, in Safety tips when disassembling old electronics?

Wear trainers not sling backs. Molten solder and your tootsie don't go well together.
I turn the printed circuit board component side down and wave a hot air gun over the flip side, whilst tapping the board against the edge of work bench. The result is usually a cascade of components (and blobs of molten solder).

Very therapeutic. When I'm stuck trying to work out how to do something, when everything I have tried has failed miserably, I deconstruct something electronic. No, I keep well away from psychiatrists.

You (I anticipate) won't be doing this 9 hours a day, 7 days a week - most of the nasties are long term exposure ones, so a one-off should be fine. If anything ever irritates your eyes or throat, get out of there and ventilate the place.

Jode, in Safety tips when disassembling old electronics?

Discharge capacitors before fucking with them.

leftascenter, in Safety tips when disassembling old electronics?
@leftascenter@discuss.tchncs.de avatar

Any bubbled up and leaking condenser may be acidic, don't touch it.

Soldering fumes are bad.

That's all I can think of.

Enclose0314, in What creates resistance in a circuit?

Unless you've managed to get a switch made out of superconducting material and you're working inside a liquid helium bath, everything has resistance :)

You'll have a bad time trying to measure such low resistances, so usually you can look at the datasheet for the switch you're using or for a similar switch if you need a ballpark number. You'll see an on-resistance, and a max current (since there will be arcing when you open the switch).

If you do want to measure the low resistance, you'll need dedicated meter with a kelvin connection.

shoeforthepot, (edited )

Thanks for the feedback and info, I'll know what to look for next time. Unfortunately, I purchased a tattoo pedal as the momentary switch, thinking it would be easier to operate. link Btw. thanks for clarifying everything has resistance, that concept confused me more than I thought it would.

Enclose0314,

Open it up!

They put a regular old switch inside a fancy box, but you'll be able to read the part number once you see the actual switch.

shoeforthepot,

I'll give it a go, fingers crossed.

cmnybo,

If you do want to measure the low resistance, you’ll need dedicated meter with a kelvin connection.

You can pass a known current through the switch, measure the voltage drop with a multimeter and use ohms law to calculate the resistance.

jjagaimo, in What creates resistance in a circuit?

Every material has resistance.

You can calculate a materials resistance using its resistivity and dimensions. For a simple wire, the formula is R = p*l/A, where p is resistivity, l is length, and A is area (cross sectional. Imagine cutting the wire, you'd see a circular cross section).

Some materials like copper have very low resistance.

Some materials like oil have a very high resistance.

Some materials like carbon have a resistance somewhere in between, but generally fairly high.

Resistors use a strip of carbon to make a high resistance path.

Resistance in a switch is typically minimized by design, so introducing a switch or button should not introduce a lot of resistance. It is tyically better not to use switches of this type in signal critical or high power applications (e.g. sound or battery charging), but charging up a small capacitor or powering a small dc circuit should be fine

To measure resistance, one can use a multimeter. This makes use of Ohm's law. Ohms law shows that

V=I*R

Where V is voltage, R is resistance, and I is current. When a small voltage is applied across your component, the current is measured. Then using the current and voltage, it can figure out what the resistance is. It shows it to you on a display so all you have to do is touch the probe tips to the two legs of the switch.

For a switch this will typically be less than 1 ohm. If you buy from a reputable distributor (e.g. digikey, mouser, arrow, farnell, even LCSC) you can get the "datasheet" and look for the constact resistance. This might be a bit harder with ebay/amazon/aliexpress parts, so just stick with a multimeter.

A cheap handheld one is fine, but I'd say prob look for an EEVBlog or other video looking at good cheap meters; you can get pretty good stuff without breaking the bank. Don't stress over it though; any multimeter is better than no multimeter

shoeforthepot,

Awesomesauce! This is exactly the clarification I needed as I unfortunately got my part from a less "reputable", that being Temu, source.

HewlettHackard,

What are you switching? There’sa good chance (but no guarantee) even an ultra-cheap switch is fine.

shoeforthepot,

A 12 volt battery w/ a pot and a few other components. The plan is it wont be running more than 5 milliamps through it. I ended up getting this so not exactly a conventional momentary switch.

Susan_B_Good,

That is pretty much exactly a conventional momentary switch. It just happens to be packaged for use controlling something a little different.

It should be fine for your application.

One thing to note - the contacts will probably "bounce" as the switch is closed. Produce a string of momentary connections and disconnections for, oh, say the first few thousandths of a second. That's perfectly normal for a mechanical switch.

That won't matter in its intended application. But if you are using it with electronics, say counting the number of times the switch is operated - the results can be unexpected.

You can look up "debounce" to see how this can be worked-around.

shoeforthepot,

Thanks, I appreciate the clarification on the switch just having a different housing. I'll have to do some further research on "bouncing", interesting stuff.

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