Unanswered Questions

16,187 questions with no upvoted or accepted answers
14
votes
2answers
3k views

DRC tool for Gerber files

Do you know any tools which perform design rule checking for Gerber files of PCB and are suitable for using in batch mode on a remote server? Something similar to what BatchPCB or FreeDFM uses (I ...
12
votes
0answers
478 views

Switch from JTAG to SWD with bitbang sequence on STM32F103VB

I am trying to switch from JTAG to SWD without any external devices. Why? Because I would like to use the SWO pin to send a stream of logging information to another device. To accomplish this ...
9
votes
2answers
5k views

STM32F407 + LAN8720A + lwIP + FreeRTOS = No received Ethernet frames

I'm trying to bring up a PCB that uses an STM32F407 and LAN8720A Ethernet PHY, and I can't seem to receive any Ethernet frames — even though I have no problem transmitting frames. Hardware setup I ...
7
votes
0answers
212 views

What's this noise?

As in other years at precisely this time I'm experiencing an effect somewhat like GSM frame-rate audio breakthrough in my auditory systems - completely different frequencies but equally wideband. I've ...
7
votes
4answers
258 views

“Temporary boost” supercap

I have a 12VDC load (up to 10A) that functions correctly down to 8VDC. Sometimes (frequency: many seconds max, many minutes typical) the power source has a very brief (few milliseconds) drop to 7V. ...
7
votes
2answers
434 views

Ultra Low Consumption White LED Flasher

simulate this circuit – Schematic created using CircuitLab I need an LED flasher circuit to operate inside small model lighthouses. Ideally the flash needs to be white and the battery needs to ...
7
votes
1answer
576 views

Design of cavity filter

I try to design a Chebyshev bandpass filter for 6 GHz as a coaxial cavity filter. I know that the filter can be designed with the aid of the coupling coefficients between the resonators and the loaded ...
6
votes
1answer
92 views

Is there a color standard for painted toroidal magnetic cores?

Is there a color standard for painted toroidal magnetic cores ? I noticed that yellow-white usually means a powdered iron core with a relative permeability of around 100 at frequencies below 10kHz. ...
6
votes
0answers
123 views

Long-tailed pair - gain and bandwidth

I'm trying to understand this schematic of this differential probe: I marked some blocks. I have some questions about the block I marked "Long-tailed pair" (LTP). I have no experience with LTPs so ...
6
votes
2answers
192 views

White and Pink Noise Generator Circuit - Cryptic AC Analysis

The “Electronic Devices and Circuit Theory” book (by Boylestad, Nashelsky) gives a brief description of a random noise generator circuit at the end of “BJT AC Analysis” chapter. (Btw, exactly the same ...
6
votes
1answer
183 views

Wireless Power Transfer for a toothbrush

The general idea is to charge a cordless toothbrush from 12V DC, instead of the mains. I have used a simple circuit that I more or less lifted from a Linear AppNote/Demo manual (DC1969). I would like ...
6
votes
1answer
199 views

DDR3 Data Errors

I am looking for post layout solutions for DDR3 data errors. I have a PCB with a FPGA and a 2 banks (2 rank) DDR3 ram setup. Data errors occur either when the RAM (FPGA is not confirmed, but could ...
6
votes
1answer
170 views

Can somebody please explain to me the principle of a T-T Earthing system?

How are the transformer, consumer's side and the generator earthed in a T-T Earthing system? I seem to understand that the generator and its frame should be earthed separately; The neutral of the ...
6
votes
1answer
145 views

VHDL Procedure - Same variable for input/output parameter

I've written a component where I use the same variable for the input and output parameter of a procedure. A reduced example looks like this: ...
6
votes
0answers
170 views

Contact a very small area (impedance matched)

In my current project, I want to apply a voltage to a capacitor (top electrode on a thin film heterostructure) very rapidly. Since capacitors have their own charging rate \$(\tau = R \cdot t = R \cdot ...

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