Recent Posts

1

Microcontrollers / Re: RIP Z80

« Last post by nimish on Today at 05:13:39 am »

Even RISC-V is kind of stuck here, CLIC isn't ratified yet either.

Not ratified, true, but frozen and very unlikely to change. It's currently in ARC (Architecture Review Committee) review, after which it needs Committee Chair and CTO sign-off, then a public review period, then the ratification vote. My guess is ratification will be around July.

Cool, I hope it'll work with the sifive/t-head/WCH implementations. I really would not want stuff like https://discourse.llvm.org/t/rfc-prestacked-annotation-to-solve-risc-v-interrupt-stacking-mess/74120 proliferating

And a standardized debug adapter interface like ARM's SWD/DAP/coresight would be great too. Who the hell wants a different *-Link for every vendor?

2

FPGA / Re: Analog video output with FPGA ?

« Last post by Jaunedeau on Today at 05:13:20 am »

Just a random thought but : if I implement on an MCU instead of an FPGA (or use and FPGA that can implement an ADC), could a 9 or 10 bit (instead of the 8 required) bits ADC plus an autocalibration routine at boot be a good solution ?

3

Programming / Re: Angle wrapping in code, "easy" problem, need to double check

« Last post by ejeffrey on Today at 05:13:17 am »

mathematical” modular arithmetic is not inherently positive either

Obviously it's a matter of terminology and the only 100% unambiguous thing is to do is show the formula, but most sources use the word "remainder" to mean the thing that C and C++ does (share the sign of the dividend) and "modulo" mean the version where the result takes the sign of the divisor.  This includes the C standard which does call the result of the % operator the "remainder."  If you do "integer arithmetic modulo N" there are only N distinct values.  in C and C++, x % N can take on 2*N-1 possible values, which means that most of the distinct values have two possible representations.  Yes, it's a choice, but pretty inconvenient if you are doing anything you call modular arithmetic.

The behavior of / and % is defined by this single identity: (a/b)*b + a%b == a

That is rather missing the point.  Everyone agrees that that the above formula has to be true for any sensible definition of %, and was required even in C89.  What C since C99 specify is that integer division truncates to zero rather than floor towards -infinity.  Once you specify division that way, in order to satisfy this formula you need to have negative numbers produce a negative remainder.  The other possible convention (and the one I would argue is far more commonly what you want) is where integer division is floor division, and the % operator acts like modulo.

4

Repair / Re: Mig welder wire feeder controller board not working

« Last post by coppercone2 on Today at 05:06:12 am »

there has got to be a better filter then a foam ear plug. maybe a fine nylon brush?

its such a dodgy construction worker hack

I don't like it because theoretically something can get stuck in the foam and scratch up the wire, and it can soak up grease and smear it on etc. I feel like a nylon brush would brush off debris and result in cleaner wire

there must be a more professional engineering solution to this using better hardware

5

FPGA / Re: Analog video output with FPGA ?

« Last post by Jaunedeau on Today at 05:05:16 am »

Hdmi to vga would be an option, and probably what I will do in early stages since I will prototype on tang nano 4k board. One problem that sourcing one that introduce low lag might be a problem on the cheap ones (e.g. one could be good, then they can change the component in the same product). Also some seems to only support full hd, and might cut some cost saving possibilities when I aims only for CGA.

Dedicated DAC seems to be the way to go... I'll use one and hope it stays available in the futur

6

Test Equipment / Re: Siglent SDS2000X Plus - Bugs / Missing Features / Feature Requests

« Last post by BillyO on Today at 05:01:33 am »

Interesting proposal though, I wonder if the HW supports backlight OFF.

It is under UI control, so that does imply the HW is subject to the SW.  This should be possible.

7

Test Equipment / Re: Siglent SDS2000X Plus - Bugs / Missing Features / Feature Requests

« Last post by tautech on Today at 04:57:38 am »

I'm into the habit of winding back brightness to 80%.......for no good reason other than not needing full brightness.

Do you have any idea about my question: Is there a reason the screensaver doesn't shut off the backlight?

Zip/zero.
Interesting proposal though, I wonder if the HW supports backlight OFF.

8

Test Equipment / Re: Siglent SSA 3021X... Ooops

« Last post by tautech on Today at 04:55:28 am »

Its already in pieces. I was doing some tx measurements and left my attenuator out when making a change. The SA got 6 Watts pumped into it. It is not working properly now, levels are wrong, frequency is also off a little, I worry that might be a bigger issue. Measurements were fine until my screwup.

Shame. 

Really we need screenshots to advise.
Normally damage to the front end results in 20dB error however I have one here that won't show any RF In levels. 

Here's one of a few mistake/damage threads:
https://www.eevblog.com/forum/testgear/what-happens-when-you-blow-the-input-of-a-6500-siglent-ssa-3075x-plus!/

9

Repair / Re: Mig welder wire feeder controller board not working

« Last post by TERRA Operative on Today at 04:53:57 am »

Here's the Service manual for the feeder and other documentation I could find.
(Linked here in my Google drive too, the welder service manual is too big to upload here)
If you let me know the 6 digit model number of your welder, I can check if I have the exact manuals. I assume it is probably 706118?

I see the schematics for the wirefeeder, including board level components etc are in the service manual which is nice.

Page 17 has the voltages, and from page 18 has a troubleshooting guide that should help narrow down the problem a bit.

I would first disconnect the feed motor from the control board in the feeder and briefly apply voltage (24V) to ensure it is not jammed or seized, and give the motor a sharp tap with the handle of a screwdriver to loosen it up if something is stuck. Also check the brushes aren't worn or stuck.

As an aside, make sure your rollers are free to turn (grease the shafts they spin on), and the gears aren't worn as they can start to jam if the teeth are badly worn. Also make sure the wire path and grooves in the rollers are kept perfectly clean for best grip on the wire.
Poking the wire through a foam earplug before it enters the feeder assembly is a cheap trick to keep the wire clean as it goes through the rollers.

10

Beginners / Re: Jutter calculation ?

« Last post by bdunham7 on Today at 04:52:46 am »

When you generate a square wave or pulse with DDS signal generators at anything but a submultiple of the DDS clock, you'll get varying rise times but the AWG will typically try to minimize the jitter as measured at the zero crossing or the midpoint of the waveform if it isn't symmetrical around zero.  IOW, that really isn't jitter, at least not it the way that it is typically defined.