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by ghellquist
Sat Mar 07, 2020 11:18 am
Forum: General discussion
Topic: Which Raspberry Pi to buy?
Replies: 21
Views: 1001

Re: Which Raspberry Pi to buy?

My two cents. I get a picture in my head where you fill a RAM with the wave form in good time ahead. No hurry there and not much need for computing speed. You the "play" that waveform at GHz playback rate. I would probably look inte using a PC video card for the playback. A 4k video signal is well i...
by ghellquist
Sat Aug 18, 2018 7:50 am
Forum: General discussion
Topic: 4-20mA output
Replies: 16
Views: 6884

Re: 4-20mA output

Not a suggestion for buying, only a link to a product under for sale:
https://www.raspberrypi.org/forums/view ... 3&t=218521
//Gunnar
by ghellquist
Wed Jun 20, 2018 5:38 am
Forum: General discussion
Topic: Cheap Networking
Replies: 12
Views: 1184

Re: Cheap Networking

Do consider the speed you want, Raw speed on Ethernet 10 MBits/sec meaning 10,000,000, raw speed on serial perhaps 115,200.
by ghellquist
Tue Jun 19, 2018 4:28 pm
Forum: Advanced users
Topic: Pi3 as master, multiple Pi Zero W's reporting in... ... ...
Replies: 11
Views: 1378

Re: Pi3 as master, multiple Pi Zero W's reporting in... ... ...

We are absolutely trying to help you. But to us the requirements seems a bit hazy. They might be read as, when misunderstood: I have a greenhouse. I want to fill it with sensors and Raspberry Pi-s. I guess what you are trying to actually achieve is something slightly different. My guess is something...
by ghellquist
Sat Jun 16, 2018 5:59 am
Forum: Advanced users
Topic: Trouble with real-time code
Replies: 15
Views: 2206

Re: Trouble with real-time code

Is there a difference if you use isolcpus?
by ghellquist
Sun May 20, 2018 8:24 am
Forum: General discussion
Topic: Just throwing this out there: backdir
Replies: 26
Views: 2430

Re: Just throwing this out there: backdir

In one of my projects I use git exactly like this. No need for internet access and only a few commands to know. Understand that git and github is not the same thing --- GitHub adds a lot on top of git which you might elect to use or not. Preparation Create the folder where the project will be. Give ...
by ghellquist
Sun May 20, 2018 8:10 am
Forum: General discussion
Topic: Set up your WordPress Database
Replies: 2
Views: 767

Re: Set up your WordPress Database

It helps if you include a link to the instructions your are following, or even better, copy them in you question. The databas mysql is used to store information used by the wordpress code. There is nothing special about that installation, but there are a number of steps you need to follow. It might ...
by ghellquist
Sun May 20, 2018 8:03 am
Forum: General discussion
Topic: Problem on MAX30105 sensor on Raspberry Pi 3
Replies: 14
Views: 1982

Re: Problem on MAX30105 sensor on Raspberry Pi 3

To other posters answering. There is a link to the actual bord the OP wants to use. As OP stated beting a beginner, we could be slightly more helpful here. The board can be directly attached to the Pi. The site says that you can run the board from 3,3V. One of the LED-s on the board will not work, ...
by ghellquist
Sat May 12, 2018 11:43 am
Forum: General discussion
Topic: Where to start? Do I use python for creating things or would I be better using JS or C or C++?
Replies: 15
Views: 1815

Re: Where to start? Do I use python for creating things or would I be better using JS or C or C++?

The most important factors in selecting a language, in my mind, are: 1- The support libraries that you easily use to tackle parts of your application. As example, if you need to manipulate pictures there are libraries that help with that. No need to write the code yourself. 2- The support you can ge...
by ghellquist
Tue Apr 24, 2018 4:27 pm
Forum: General discussion
Topic: Are Raspberry Pi and other microcontrollers scalable for commercial projects?
Replies: 13
Views: 1534

Re: Are Raspberry Pi and other microcontrollers scalable for commercial projects?

As one example you might look into OpenEnergyMonitor.

One setup uses temperature / humidity sensors powered by an Arduino. The emonTH then sends its data, sort of a few times a minute, over radiowaves. The central unit can be an RPi. Battery should last something like a year I believe.

/Gunnar
by ghellquist
Sun Feb 04, 2018 10:14 am
Forum: General discussion
Topic: Powered by XLR cable "Phantom Power" (+48V 14mA)?
Replies: 35
Views: 4379

Re: Powered by XLR cable "Phantom Power" (+48V 14mA)?

It will not work.

Phantom power is delivered to microphones starting with 48V. It goes through a resistor of 6810 Ohms. The power deriverad this way will not be sufficient to power a Raspberry.

https://en.wikipedia.org/wiki/Phantom_power

/Gunnar
by ghellquist
Sat Jul 15, 2017 9:24 am
Forum: Advanced users
Topic: Raspberry pi Zero - Analog audio input
Replies: 9
Views: 9057

Re: Raspberry pi Zero - Analog audio input

A bit off topic. But a bit of facts. Admittedly a bit simplified. Signal to noise rate is approximately 6 db per digital bit. The S/N then is the difference between the maximum signal and the "floor" of noise. CD-s are 16 bits, giving approximately 96db of S/N. There are no commercial audio converte...
by ghellquist
Sat Jul 15, 2017 9:13 am
Forum: Advanced users
Topic: Multiple pi cameras
Replies: 6
Views: 1284

Re: Multiple pi cameras

You will need to think about how much "jitter" you can accept in when the pictures are taken. For extreme precision, say below milliseconds, I am not sure you can make the standard Pi camera to react that fast. This will influence how you trigger the picture processes in the network of Pi-s. Dependi...
by ghellquist
Sat Jul 15, 2017 9:06 am
Forum: Advanced users
Topic: Raspberry Pi3 remote connect to PLC
Replies: 1
Views: 1649

Re: Raspberry Pi3 remote connect to PLC

This is definitely doable with a RPi. Telling us which type of PLCS might help us help a little better. Some ideas. - the PI has delicate digital inputs, so you will need some extra hardware to protect it. The Pi inputs are max 3.3 V. There are a lot of different solutions which you can buy ready-ma...
by ghellquist
Tue Jun 06, 2017 10:01 am
Forum: General discussion
Topic: Pi vs Microcontroller? (+Interrupts)
Replies: 28
Views: 9794

Re: Pi vs Microcontroller? (+Interrupts)

There is a function I have contemplated to investigate. The function isolcpus in Linux allows us to reserve one (or more) CPU-s. Since the rpi 2 and 3 has four CPU-s, we could reserve one for realtime work. A control loop could run there, more ore less isolated from the rest of the Linux system. The...
by ghellquist
Sun May 22, 2016 8:08 am
Forum: Networking and servers
Topic: How could I host a website totally on my R pi ?
Replies: 6
Views: 16963

Re: How could I host a website totally on my R pi ?

You will need four things. 1) The OS Raspbian will be fine (the supported "standard" for Pi) 2) Install the programs Search for LAMP - Linux, Apache, Mysql and PHP Apache is the web server Mysql the database PHP one common language used on web sites 3) Create your website Writing html is one way to ...
by ghellquist
Thu Apr 28, 2016 4:36 am
Forum: Beginners
Topic: I2C read starts from arbitary register
Replies: 10
Views: 2412

Re: I2C read starts from arbitary register

Reading the data sheet, it says the following. 1) Tell the device which adress you want to read from. This requires you to send three bytes of data: device select, address byte, address byte. Here the R/W bit should be 0 in the select. 2) Read the data: You send device select, the devices responds w...
by ghellquist
Sun Mar 13, 2016 9:19 am
Forum: General discussion
Topic: 4x4 membrane keypad
Replies: 13
Views: 4850

Re: 4x4 membrane keypad

I believe what you experience here is real world vis computer program. In order to read the ROW input you need to wait for the electrical signals to calm down. So insert a short delay after outputting COL until reading ROW.

/Gunnar
by ghellquist
Sat Jan 16, 2016 8:13 pm
Forum: Raspbian
Topic: How to build / Re-configure My own OS for the raspberry
Replies: 6
Views: 1266

Re: How to build / Re-configure My own OS for the raspberry

Hi all :) , ... I don't know if doing this will improve the performance of the pi ... Any help will be appreciated :) It is a very interesting thing to do. But it will not improve the performance. Basically "stripping" the OS of modules will not help you in this case. The modules does not take any ...
by ghellquist
Wed Dec 30, 2015 4:42 pm
Forum: General discussion
Topic: Raspberry Pi Zero Cluster
Replies: 8
Views: 1956

Re: Raspberry Pi Zero Cluster

Short answer: no. Longer answer: Each Pi Zero is a slow computer. Very nice for learning programming and such. Extremely slow for most normal PC usage. Having several in a cluster does not help with normal PC usage at all. So, if you want to learn about clustering and dividing software algorithms on...
by ghellquist
Sat Aug 22, 2015 9:58 am
Forum: General discussion
Topic: Setting hostname dymanically
Replies: 21
Views: 10651

Re: Setting hostname dymanically

Please share some light to me. Why would each box need its own host name? What and where is it used?
The router will give each machine its own IP adress, could not care less about host name.
Just asking.
// Gunnar
by ghellquist
Wed Jul 15, 2015 8:28 pm
Forum: General programming discussion
Topic: RPi as car ECU?
Replies: 33
Views: 38187

Re: RPi as car ECU?

Oops. What negative talk. Let us keep things positive, I believe the OP knows or will find out about the problems in due time. It should be possible to do an ECU using a Pi. Not easy of course but why tackle easy thing. I believe you would need a few added pieces of hardware, such as AD and DA conve...
by ghellquist
Wed Jun 24, 2015 9:15 pm
Forum: General discussion
Topic: Redundancy
Replies: 21
Views: 6204

Re: Redundancy

Too little information from the original poster. Of course you could make a redundant system with Pi-s. But not any redundant system. It will take some extra hardware, possibly a lot of extra hardware. Answers to a few of these questions might help in trying to give an answer. Each answer will influ...
by ghellquist
Sun May 24, 2015 8:02 am
Forum: Networking and servers
Topic: I want to start my 1st rasberryPi project
Replies: 4
Views: 955

Re: I want to start my 1st rasberryPi project

Alright, so now should I install an Operating system like Fedora / NOOBS / Raspian? Yes. It saves you a few years of frustrating hard work in order to get anything at all running on the Pi. and program C/C++ onto it? If you want to, yes. Personally I like to go a bit more "high-level" as to languag...
by ghellquist
Sat May 23, 2015 1:31 pm
Forum: Networking and servers
Topic: www and Tornado websocket server
Replies: 6
Views: 2301

Re: www and Tornado websocket server

I set forwarding on my router: port80->Rpi IP address (192.168.1.103). The router has a totally different adress on the internet and translates that adress using NAT. You need to point your phone to the current router adress (connect to the router and check which adress it has). There are two probl...

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