Costume linux scheduler for Raspberry pi - raspberry-pi

I am using Raspberry pi and I want to get a digital sign when a specific process runs, to trigger another measurement tools (e.g oscilloscope or spectrum analyzer) to start measure things.
I didn't find any workaround to do it (If you know any please share) so I want to create a costume scheduler.
My plan is to create a process with special priority and whenever the process gets CPU time I want to turn on a GPIO and when the process is preempted I want to turn off the GPIO.
How would you recommend to start implementing it? are there any existing open source projects which did something similar?
Any help would be appreciated.

Related

STM32L151c8t6 PCB design problems (nrst)

hi we haveseveral boards in need of the stm32L151C8t6 and we have some stock of the mcu in question the problem is that all the pcbs 'from JLCPCB' have this weird issue were the mcu is stuck and i have to manually poke thenrst pin multiple time for it to run normally "poke as in pull it to gnd for it to reset " please i need help with this i'll share some the the designs
example 1:
PCB design
example 2:
PCB design
made a dac output from 0 to max
start the program nothing happens
try to jump the nrst multiple times until it starts
using stm studio and changing a value i in the program so i can see where it stopped
video explaining
Video

Problem programming and running STM32F103C8

I'm facing an unexpected problem with stm32f103c8. I'm programming the chip and after reset, it starts to run the program, but after a few seconds the microcontroller getting mixed up and stops running the program. After that when I try to reprogram the microcontroller, IDE(IAR EWARM) tells "target held in reset state".
It's very unusual issue because sometimes when I connect nRST pin directly to the VCC(3.3V), microcontroller runs program but unfortunately the current goes over 120mA and chip breaks down finally.
I'm using STM32CubeMX to generate the codes and my programmer is STLINK V2(clone), also tried Jlink V8.0(clone) but didn't change the result.
Could it be because of the clone programmers?
Can anyone help me solve this problem?
Thanks
Never connect nRST directly to VDD/VCC. This is a bi-directional input-output which must only ever be connected to an open-drain/open-collector signal. It can be pulled low externally or from within, it must never ever be pulled or driven high other than by the internal pull-up resistor.
When your debugger or programmer has finished programming the flash and wants to start running the new program then it requires to be able to pull this line low, which it might do externally if you connect this line to it in hardware, or else it has to be able to pull it low by software using the internal reset pulse-generator. If it does this and you have tied the line high externally then you are effectively shorting out your power supply, which is the cause of the over-current condition that you have observed.
Maybe the original problem is that your counterfeit ST-Link has its reset output configured as push-pull when it should be open-drain.
I would suggest that the easiest way to proceed is to leave the nRST line unconnected and configure your programming tool to use a software reset only.

RPi Pyaudio/Portaudio + ALSA: How to select/change mux inputs

I'm working on a project that is using a Raspberry Pi with Raspbian and an SGTL5000 based sound card (FePi.) I have no problem selecting the card and getting samples in both directions - once I have configured the multiplexer to properly select line In/Out. I did this with Alsamixer. I want to automate the process so that the only step required is to run the application.
I don't see a way to do this using PyAudio/PortAudio. Is my only option the ALSA API or is there a way to do this with PyAudio (or PortAudio) that I'm not spotting?
Thanks in advance for any insight you can provide.
Oz (in DFW)
I ran into a similar problem, I wanted to automate changing mux settings but I wanted to adjust inputs not exposed by alsamixer too.
To deal with the limitations of the driver I ended up porting over the Teensy 3.x sgtl5000 control software to the pi yesterday
https://github.com/Swap-File/pi-sgtl5000
You could force feed the same commands via i2c via python.
The only downside is, once you start force feeding the sound card i2c commands, you break alsamixer (and anything else that might try to adjust it's own volume settings).

Is it possible to send realtime commands from PC to PLC

We are using a frequency inverter to power a servo motor. This has to be programmed using PLC. Is it possible to gather data from a running program, using values from that to control the movements / frequency of the inverter?
(as an example; We built a racing game, we'd like to build a simulation chair that can support a grown person and act on accelaration / braking etc in the game)
Thanks
Yes, I believe what your asking is possible. I personally use a VB script running on a PC to write to registers in a PLC... so that's one way to do it.

Can an NXT brick really be programmed with Enchanting and adaption of Scratch?

I want my students to use Enchanting a derivative of Scratch to program Mindstorm NXT robots to drive a pre-programmed course, follow a line and avoid obstacles. (Two state, five state and proportional line following.) Is Enchanting developed enough for middle school students to program these behaviors?
I'm the lead developer on Enchanting, and the answer is: Yes, definitely.
The video demoing Enchanting 0.0.4 shows how to make a proportional line follower (and you could extend it to use a PID controller, if you wish). If you download the latest version, 0.2.2, it includes a sample showing a two-state line follower (and you can see a video and download code here). You, or with some instruction / playing around, a middle-schooler, can readily create a program to do n-states, and, especially if you follow a behaviour-oriented approach, you can avoid obstacles at the same time.
As far as I know, yes and no.
What Scratch does with its sensor board, Lego Wedo, and the S4A - Scratch for Arduino - version as well as, I believe, with NXT is basically use its remote sensor protocol - it exchanges messages on TCP port 42001.
A client written to interface that port with an external system allows communication of messages and sensor data. Scratch can pick up sensor state and pass info to actuators, every 75ms according to the S4A discussion.
But that isn't the same as programming the controller - we control the system remotely, which is already very nice, but we're not downloading a program in the controller (the NXT brick) that your robot can use to act independently when it is disconnected.
Have you looked into 12blocks? http://12blocks.com/ I have been using it for Propeller and it's great and it has the NXT option (I have not tested)
It's an old post, but I'll answer anyway.
Enchanting looks interesting, and seems to be still an active project.
I would actually take the original Scratch (1.4), as it's is more familiar and reliable.
It's easy to interface hardware with Scratch using the remote sensor protocol. I use a simple serial interface (over a USB-adapter) which provides 3 digital inputs and 3 digital outputs. With that, it's possible to implement projects such as traffic lite, light/water/heat-sensors, using only lets, resistors, reed-contacts, photo-transistors, switches, PTSs.
The costs are < 5$
For some motor-based projects like factory belts, elevator, etc. There is not much more required, a battery and a couple of transistors/relais/motor driver.