Raspberry Pi Forums

experix

You seem to be misunderstanding something. No modern OS is going to work on a CPU doesn't have interrupts. How would it do context switching? How would it know when to read the keyboard and mouse? How would it know when there is service needed on the network, USB and other stuff?

experix

I suppose you want to do this because a camera board can deliver performance advantages relative to a USB camera. What are the important advantages, and how big will they be for the RPi?

experix

The thermostat is probably an on-off switch that gets moved by the shape change that temperature change causes in a bi-metallic strip. Probably a relatively low-level current flows through this switch, and that goes through a relay to switch the high current for the bioler. If you are only trying to...

experix

dev/random blocks while the entropy pool is empty, but if pseudo-random numbers are good enough you can use dev/urandom, which is the same as /dev/random until the entropy is gone, then it switches to a deterministic pseudo-random algorithm. See more in man urandom.

experix

You can write a C program that contains arbitrary bytes in the instruction stream. I don't remember what the appropriate directive is for gcc-- maybe 'emit', like what I used with another compiler? Actually it occurs to me that I probably did this sort of thing within an 'asm' block. I'll have to lo...

experix

I did a bunch of comparisons using various PCs, a Pi B+ and a Pi 2, all running http://experix.sourceforge.net (a scripting language for device control and data acquisition and analysis) and doing these tests: generating ramp and sine functions (also compared vs. octave on a Linux PC) generating a b...

experix

Viewing a 10 MHz square wave, you have to be careful about cable impedance and impedance matching at the oscilloscope input in order to avoid echoes. Have you checked that you can see a good-looking square wave from something that you know is producing one?

experix

On Sierra Club trailbuilding outings (camping for a week in a remote place) we put a roll of TP on a stick at the trail to the latrine, and a person wanting to use the latrine would see that the TP is there, and go and take it, then put it back when done. In your situation maybe you only need a swit...

experix

I have encountered this kind of obstacle many times. I suppose your NIR sensor is a USB device or internet device, and in either case if you have the communication protocol or can convince the manufacturer to divulge it, you can make your own software. Or if you can get the source code, maybe you ca...

experix

Assuming that file exists on your system, you could tell the compiler where to look for #included stuff by using a '-I' directive, or you could edit the source files to show the complete path to it, or maybe you just need to 'cd' to the directory that contains the opencv2 directory. Maybe there is a...

experix

If a memory region can be written by an interrupt handler or even directly by hardware, you declare it volatile so the compiler takes appropriate precautions. If you then do your own writing to it, such as by memset, you take the chance that the interrupt might happen while you are doing that, and r...

experix

The OP doesn't seem to have a solid grounding in thread usage, and his question comes across as a request for 1-on-1 tutoring, which probably isn't going to happen. The man pages are more helpful to people who already have some familiarity with the topic and need to review it and be reminded of deta...

experix

As for sourceforge, there is nothing of value there. I beg to differ. It is true that there is a huge volume of stuff on SourceForge and finding something relevant to your needs can be a daunting challenge. However, I have downloaded and installed several packages that proved very useful to me. And...

experix

According to man pthread_create, it can fail with EAGAIN if there are insufficient resources to create the thread. (It can also fail with EINVAL or EPERM, but the fact that it is working most of the time seems to rule out the causes of those errors.) You seem sure that there are not too many threads...

experix

This is unclear. What do you want to do? What is a pulse sensor? If you want to connect it to an ADC, I suppose its output signal must be a voltage that varies with time, and you want to examine such things as the maximum, the duration, the envelope shape and so on. Then you need to start with the e...

experix

I gather that this is a module which you wrote. It seems to have tried to make an illegal memory reference in a function called uart_begin. If you can't find an error by inspecting the C program, you need to look at the disassembled code surrounding the address where it crashed, and in particular th...

experix

I needed to operate a Gertbot (which uses serial communication for everything) at high speed. Sending or receiving in bulk is not an option because you have to send a little command and then get a little answer, and so on. But the operating system interface is a big (or should I say little?) bottlen...

experix

If you look up 'man acos' it gives you this info at the top:

Code: Select all

#include <math.h>
and
Link with -lm

What I don't know is why your linking went ok before. Something somewhere must have told the linker to link the math library. I would like to know where defaults like that come from.

experix

The Gertbot has 4 H-bridges rated 2.5A, and you can certainly get H-bridges alone if you want to build your own thing. And there must be other boards out there that have bridges with enough capacity for you. Your remark about putting resistors in series with the motors suggests you may have chosen m...

experix

If this is the biggest issue you can find, it must be a **really** good system!

experix

I needed to get faster action on the serial port than what could be achieved by reading/writing /dev/ttyAMA0 (the userland-kernel transition was eating up too much time when I tried to control hardware using short messages back and forth). I wrote a userland tty driver and got about 7x speed improve...

experix

You have two exposure problems to contend with. The sky has big differences in brightness from horizon to where the sun is, and the fisheye lens probably has a big difference in exposure between the center and periphery. Maybe you can adjust your shutter speed to avoid saturating too much of the cen...

experix

If the purpose is to get an image size (pixel dimensions) smaller than the camera sensor dimensions, you can reduce the original image by cropping (if you only want a part of it) or by transforming the whole thing into smaller pixel dimensions. ImageMagick can do both of those. Or you may get a big ...

experix

I think your are better off controlling the gain of the amp, not the input signal.

experix

I also don't know the answer-- I only know more questions. When you speak of intensity, would that be photons per second, or power? For any particular color these are proportional, but the factor depends on the color. Or maybe you are more interested in the electric field strength. That is related t...

Search found 204 matches

Re: No interrupt?

Re: new PI camera module

Re: Raspberry pi central heating

Re: Random Number Generator Using Build In Hardware

Re: Binary not working

Re: Benchmarking a raspberrypi compared to my own PC

Re: Low Level Register Access for Clock Signal: No square wa

Re: Toilet detector ...

Re: Raspi2 and NIR Spectrometer

Re: opencv problem

Re: memset problem

Re: pthread questions

Re: Too weird, No apps for install.

Re: pthread_detach causing SIGBUS: Bus error

Re: Setting up the pulse sensor for the Pi

Re: kernel error

Re: reading serial data from sensor

Re: Problem linking to trigonometric library.

Re: High Current Stepper Control

Re: Another Usability issue

Re: Serial - Send a character

Re: How can I get the exposure time of Pi camera?

Re: Another question about the RasPi Camera

Re: Sound Advice?

Re: Picam respond linearly as a function of light intensity?