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by experix
Thu May 05, 2016 12:49 pm
Forum: General programming discussion
Topic: Problems with Linux Shell Scripts!
Replies: 6
Views: 986

Re: Problems with Linux Shell Scripts!

Was the assignment "understand the problem and write a program to solve it", or was it "find an answer somewhere on the web and copy it without understanding anything"?
by experix
Tue May 03, 2016 1:27 pm
Forum: Automation, sensing and robotics
Topic: [RP3] measuring speed
Replies: 2
Views: 598

Re: [RP3] measuring speed

I'll expand a little on what scotty101 said. The accelerometer cannot measure speed. What it measures is change of speed, that is, acceleration. You have to integrate that over time in order to get the present speed relative to the speed you had when you started integrating. That will accumulate err...
by experix
Fri Apr 22, 2016 12:47 am
Forum: General discussion
Topic: Raspberry Pi - Data logging
Replies: 7
Views: 1305

Re: Raspberry Pi - Data logging

"data logging" is a huge category. Nobody can tell you how to do "data logging". Start with a defined problem, and you can get lots of hints about what to use and how to use it.
by experix
Sun Apr 17, 2016 2:49 pm
Forum: Automation, sensing and robotics
Topic: Running Various Programs at once
Replies: 2
Views: 522

Re: Running Various Programs at once

Another way is to run them in separate terminals or x-terms. That way their outputs don't get mixed up and it's less confusing to run them than when you use "command1 & command2" in one terminal.
by experix
Tue Apr 12, 2016 2:26 pm
Forum: Advanced users
Topic: Changing the behaviour of cleaning tmp-files
Replies: 3
Views: 575

Re: Changing the behaviour of cleaning tmp-files

I don't have my pi available now, and somebody will probably give you exact info on this-- but you might try this: search for a phrase from the message in all files under /etc, for example grep -r a_word_from_the_message /etc If you find it, you can probably figure out how to alter that file. Tip: s...
by experix
Thu Apr 07, 2016 3:01 pm
Forum: Automation, sensing and robotics
Topic: calculating conductivity of water by pi
Replies: 3
Views: 950

Re: calculating conductivity of water by pi

I guess you are asking how to connect the conductivity electrode to the ADC. Can you tell us about the electrode or post a link to its data sheet?
by experix
Wed Apr 06, 2016 2:05 pm
Forum: C/C++
Topic: Which Editor for C Programs
Replies: 33
Views: 2911

Re: Which Editor for C Programs

I like nano, especially my personal version of it, but does anybody know how to avoid the annoying slow-down that it exhibits when displaying far down in a long file, with syntax highlighting turned on? I guess the problem is that every time it needs to re-write the screen, it starts at the top of t...
by experix
Thu Mar 31, 2016 2:28 pm
Forum: Advanced users
Topic: Old electronics
Replies: 2
Views: 557

Re: Old electronics

Add this to the issues list:
figuring out or getting info on bizarre communication protocols.
by experix
Wed Mar 30, 2016 3:58 am
Forum: Astro Pi
Topic: My Sense Hat Temp/Press/Hum Readings seem inaccurate
Replies: 4
Views: 2761

Re: My Sense Hat Temp/Press/Hum Readings seem inaccurate

I made a C program that lets you measure the temperature via all three sensors on the sense hat, plus the CPU, with ability to exercise most of the options that exist. They all get different results. I have not tried comparing vs. "known" temperature. It will be some time before I can look at this a...
by experix
Thu Mar 10, 2016 2:41 pm
Forum: Astro Pi
Topic: Using SenseHAT from C
Replies: 6
Views: 2881

Re: Using SenseHAT from C

I am taking little baby steps with this and trying to explore all aspects of the problem. Consequently I have not yet gotten around to the humidity and pressure. With the help of the datasheet you should be able to adapt my code to read those things. My equipment is packed in a moving pod and it wil...
by experix
Tue Mar 08, 2016 3:15 pm
Forum: Automation, sensing and robotics
Topic: Recommendations for photodiode and signal conditioner??
Replies: 3
Views: 526

Re: Recommendations for photodiode and signal conditioner??

So you seem to be trying to make one Pi use a LED to send to the other Pi, which picks up the signal by using a photodiode. I think you need to wire up the photodiode with the usual transconductance amplifier and put the output of that into a comparator to discriminate between background and LED sig...
by experix
Tue Mar 08, 2016 1:29 am
Forum: Other projects
Topic: Raspberry as graphic calculator?
Replies: 4
Views: 936

Re: Raspberry as graphic calculator?

Check out http://experix.sourceforge.net . It's a calculator that runs scripts, and it understands some concepts not usually included in calculators, such as threads, USB device operation, timing, general file operations and lots of other stuff. It uses a stack that holds many different kinds of thi...
by experix
Mon Mar 07, 2016 2:45 pm
Forum: General discussion
Topic: UART Address mapping.
Replies: 1
Views: 429

Re: UART Address mapping.

I recall finding it fairly confusing to work with that document, but I put together a program that operates a PWM-controlled linear motor on the Gertbot. You can find my stuff at [url]https:experix.sourceforge.net[/url] in the Download files section. Get the latest experix distribution and look at s...
by experix
Mon Mar 07, 2016 2:22 pm
Forum: Astro Pi
Topic: Using SenseHAT from C
Replies: 6
Views: 2881

Re: Using SenseHAT from C

I made example programs that operate the LED matrix; get joystick input; and monitor temperature reported by the pressure sensor, temperature/humidity sensor, accelerometer and CPU. Find it in https://experix.sourceforge.net . Click Dowload source files and information , select sense-hat , download ...
by experix
Sun Mar 06, 2016 3:25 pm
Forum: Automation, sensing and robotics
Topic: How to use multiple A.D.C with raspberry pi ?
Replies: 4
Views: 818

Re: How to use multiple A.D.C with raspberry pi ?

I got a USB-1608G from [url]http:www.mccdaq.com[/url] and have done some development with it and somewhat tested its limits concerning turn-around when loading a new DAC signal. They also have ethernet-connected models. These things are a bit pricy, but really convenient to use. You can hook up 16 a...
by experix
Tue Mar 01, 2016 6:05 pm
Forum: Other projects
Topic: Liquid Cooling
Replies: 14
Views: 2412

Re: Liquid Cooling

I put mine in a beaker of freon. Works great!
by experix
Fri Feb 26, 2016 5:16 pm
Forum: Advanced users
Topic: One USB ports Raspberry Pi B+ like USB HID. Is it possible?
Replies: 7
Views: 825

Re: One USB ports Raspberry Pi B+ like USB HID. Is it possib

I don't understand the question. I looked up USB HID in wikipedia, and it speaks of standards for human interface devices such as keyboards and mice. Certainly you can use those with a Raspberry Pi. If there is a specific not-so-common thing that you want to use I can only suggest checking whether i...
by experix
Mon Feb 22, 2016 8:08 pm
Forum: Advanced users
Topic: Create framebuffer with non-square pixels?
Replies: 8
Views: 3021

Re: Create framebuffer with non-square pixels?

Thanks for the tip, drgeoff. I'll try doing that. Could be quite a bit faster, but maybe not as easy to get a bunch of different results out of one picture. (I can FT the picture, manipulate that various ways and inverse-FT those to get different filters, sizes, etc.) I looked up some articles on FI...
by experix
Mon Feb 22, 2016 5:28 pm
Forum: Astro Pi
Topic: Do I have a 'faulty' Sense Hat?
Replies: 5
Views: 2199

Re: Do I have a 'faulty' Sense Hat?

scotty101 wrote:You need to understand the mathematics of what the RTIMU library does.
Can you help us dummies by providing a reference to the relevant docs? Or source files with illuminating comments?
by experix
Mon Feb 22, 2016 5:17 pm
Forum: General discussion
Topic: Dog Intercom
Replies: 7
Views: 1155

Re: Dog Intercom

Do you mean, software that lets you talk to them via internet (I'm sure you can find that), or something you can connect to the Pi to get the sound (I would look for some sort of USB sound card), or a project that addresses the problem of making the dogs pay attention (there, I can't offer any advic...
by experix
Mon Feb 22, 2016 5:13 pm
Forum: General discussion
Topic: usb touchpad
Replies: 1
Views: 311

Re: usb touchpad

Looks like it might be worth trying. From the website you linked: Linux: Works like standard USB mouse Automatically starts working when plugged in! Tapping, Double Tapping, Vertical Scrolling, right tap, drag n drop No drivers, downloads or discs needed I have a keyboard-touchpad combo that came wi...
by experix
Mon Feb 22, 2016 5:07 pm
Forum: General discussion
Topic: catapult project ( raspberry pi ) - physics - need help
Replies: 98
Views: 9654

Re: catapult project ( raspberry pi ) - physics - need help

Your accelerometer on the projectile will give you the deceleration due to air drag (if it is sensitive enough), and it might tell you about rotation (you might want to use magnetometer readings to help sort that out), and you might get a big reading sometimes from hitting a bird.
by experix
Sat Feb 20, 2016 4:53 pm
Forum: Automation, sensing and robotics
Topic: I2C and SPI at same time?
Replies: 8
Views: 3273

Re: I2C and SPI at same time?

The sense-hat (astro-pi) uses SPI for talking to the MCU (or AVR as it is also called) and I2C to talk to the pressure sensor, temp/humidity sensor and accelerometer/gyroscope/magnetometer. I am developing a set of header files, documentation aids and test/example programs for this. You can find it ...
by experix
Sat Feb 20, 2016 4:44 pm
Forum: Advanced users
Topic: Create framebuffer with non-square pixels?
Replies: 8
Views: 3021

Re: Create framebuffer with non-square pixels?

I don't know whether framebuffer drivers have any built-in knowledge of non-square pixels. But assuming they do not, consider this: if you make a 1920x1080 pixel screen that is 3 inches by 3 feet, your 1920x1080 framebuffer will happily fill that up and you get a really skinny tall picture with ever...
by experix
Wed Feb 17, 2016 4:34 pm
Forum: C/C++
Topic: Priorities of the program
Replies: 11
Views: 3247

Re: Priorities of the program

"chrt" allows your process to wake up whenever it wants to, preempting all normal tasks. The man page speaks of selecting the scheduling policy and priority, with choices SCHED_OTHER, SCHED_FIFO, SCHED_RR, SCHED_BATCH, SCHED_IDLE, SCHED_RESET_ON_FORK for the policy. It does not say anything about w...

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