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# Unanswered Questions

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 ...
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....
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 ...
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 ...
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 ...
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) ...
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 ...
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 ...
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 ...
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 ...
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. ...
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,...
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). ...
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. ...
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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