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Unanswered Questions

14
votes
2answers
5k views

How to implement critical sections on ARM Cortex A9

I am porting some legacy code from an ARM926 core to CortexA9. This code is baremetal and does not include an OS or standard libraries, all custom. I am having a failure that appears to be related ...
11
votes
1answer
951 views

SPI transaction timeout linux device driver

I am stuck for last 3 days at a point. I am working on eink device driver with msm8960 qualcomm chipset. Scenario: In file: kernel/arch/arm/mach-msm/devices-8960....
10
votes
2answers
2k 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 ...
9
votes
1answer
338 views

Increasing the compliance voltage range for a variable, two-quadrant constant current pin-driver circuit

The following is for hobbyist work and I have no commercial intentions at all. Only a handful (two?) will be built. (I use these for part testing and curve generation, though with the higher voltage ...
8
votes
2answers
116 views

IC that would pull output to the ground, perhaps NOT gate?

I have a board with four relays on it. It has a standard Vcc, Gnd, and In1-In4 pins. I want to control it with Arduino or in my case an ESP32. However, I noticed that when output pin on my controller ...
8
votes
1answer
208 views

Why does my BLDC motor change behavior at high speed?

Background I've recorded torque vs speed performance of a small sub 50 gram hobby BLDC motor, the KDE 2304XF-2350. I power the motor at different fixed voltages to the ESC (electronic commutator) ...
8
votes
1answer
404 views

FSInit() - “CE_BAD_PARTITION”

I am using a PIC18F26K80 and an XC8 compiler. I am trying to initialise an SD card and create a file. I have simply formatted the SD card on Windows to have a "FAT32" file system and an "Allocation ...
7
votes
5answers
317 views

Practical ways to obtain Bode plots for an unknown circuit

I want to use a practical method/way where I can obtain roughly the Bode plot of a system especially a filter. This of course can be done by using complex math or implementing the circuit in a SPICE ...
7
votes
2answers
550 views

Is it really necessary to manually clear the XMEGA timer overflow interrupt flag?

As some of you may know, Atmel provides a software framework (mainly as part of Atmel Studio) that provides drivers and examples and is updated on a more or less regular basis. In a recent update ...
7
votes
1answer
472 views

Flash memory data retention time

I'd like to buy one of those after market Android car head/infotainment units. But I don't think there's a way to reinstall the system software if it gets corrupted, so I'm concerned about how long ...
6
votes
1answer
220 views

Transient drop in accelerometer gravity reading when in motion

I am using Pololu AltIMU-10 v4's accelerometer to monitor the acceleration of my system. I understand that when the sensor is placed upright on the table, it should measure 1g in the +ve z-axis. ...
6
votes
3answers
519 views

AC circuit problem

I need help with the following problem: Given the circuit of sinusoidal current (attachment 1) with given data: $$\underline{E}=100V,\underline{E_1}=40V,\underline{Z}=(10+j10)\Omega,\omega=10^5rad/s,...
6
votes
2answers
567 views

What are these connectors?

Specifically, the plug and socket at each end. This is a board-to-board cable from a 1989-era Toshiba laptop, which connects a dedicated modem port to the modem itself (not present in my laptop). ...
5
votes
1answer
103 views

Thyristor/SCR \$i^2t\$ and \$i^2\sqrt{t}\$ Rating

I have commonly seen the \$i^2t\$ rating for fusing in a SCR datasheet. This is a helpful rating for assessing if pulses which exceed the surge current rating (Itsm) of the SCR will damage it. ...
5
votes
1answer
1k 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 ...

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