Unanswered Questions

26,871 questions with no upvoted or accepted answers
22 votes
0 answers
2k 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 ...
17 votes
1 answer
938 views

What is this weird EMV pin on my credit card?

I recently got a Venmo card, which is my first card with contactless support. I was looking at the EMV pins and noticed a very weird design. In the middle of the ground pin, there is this long, thin ...
10 votes
0 answers
312 views

Speed of compound wound dc motor

This is homework. Given a 500W, 200V compound wound motor with constant shunt field and a series field that varies with armature current, how do we calculate the change in motor speed. I know the ...
10 votes
1 answer
892 views

Convert analog piezo "transition" to digital signal

I'm trying to get what amounts to a knock indication into a microcontroller input from a piezo sensor. It's looking fairly good now at the fifth iteration, and about ready to provide digital levels ...
9 votes
1 answer
263 views

Phase noise of op-amp

Suppose I have a carrier signal with low-ish RF frequency (a few MHz) that I can reasonably amplify with an op-amp. How can I estimate the added phase noise due to the amplifier? For microwave ...
8 votes
1 answer
287 views

Burned motor controllers: possible root causes analysis

On a submarine robot we built, during an operation, we recently had 3 defect thruster motors (the internal power PCBs have many burnt components, 2 of the motors cracked open due to internal pressure)....
7 votes
1 answer
414 views

Incrementing net name for group in Eagle

I want to make 50 copies of the block below, but I need incrementing numbers on each of the net labels (these will go to a connector). I do not want each block connected to the other blocks. It would ...
7 votes
4 answers
601 views

GPS power consumption MTK3339 vs SirfIII for periodic logging application

I am currently working on redesigning a SirfIII based battery operated GPS logger. A MTK3339 based GPS module has been selected due to overall (advertised) performance. The GPS logger uses a ...
6 votes
0 answers
119 views

Estimate base-spreading resistance from Gummel-Poon model

I'm attempting to calculate the base-spreading resistance of BJTs from manufacturer-provided SPICE models, which use the Gummel-Poon model. This Agilent publication (Internet Archive link here, if ...
6 votes
0 answers
168 views

Novel CAN bus design - needs criticism

I'm designing a CAN bus interface for a PCB I'm working on. CAN and high speed/long distances are new to me, so I have a list of concerns about my design ideas, and I would appreciate someone with ...
6 votes
0 answers
1k views

Is JTAG faster than SWD for debugging on an STM32F with STLINK-V3SET programmer?

There is a new STLINK-V3SET programmer that someone dropped off on my desk today. It supports USB 2.0. My thinking is that if SWD is the bandwidth limiter in the signal chain then a new programmer isn'...
6 votes
1 answer
680 views

Modeling scalar control of PMSM

I have met with a scalar control algorithm for a permanent magnet synchronous motor. I haven´t heard about it before so I decided to develop a dynamic model to further analyze this control algorithm. ...
6 votes
1 answer
157 views

Phase shift near saturation mitigation in input stage amplifier -- How does this work, why does this work?

I'm trying to understand how this circuit works on the input stage to the 4192A Impedance Analyzer. Apologies for the quality... this is the best scan I could find. The design is furnished with the ...
6 votes
1 answer
5k views

STM32 UID decoding

In my project I need to make readable 96bit UID, in reference manual is described how the number is encoded: ...
6 votes
2 answers
887 views

PWM on phototransistor

I am pulsing the VDD with 50% duty cycle at a frequency of 188 Hz (PWM). I get some weird spikes on my output TP3. Am I missing something about phototransistors? Here is the picture of the IR circuit ...

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