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by rurwin
Sun Feb 26, 2017 1:51 am
Forum: Other programming languages
Topic: BBC Basic
Replies: 70
Views: 20733

Re: BBC Basic

What use are interrupts in BBC BASIC? Are you kidding? Most modern operating systems are event-driven so a programming language needs to have a mechanism for receiving those events asynchronously. The only alternative is an old-fashioned polling loop which is hopelessly inefficient and limiting. Th...
by rurwin
Thu Feb 23, 2017 9:43 am
Forum: Other projects
Topic: Looking for a sustainable case
Replies: 32
Views: 14037

Re: Looking for a sustainable case

I know a local council (Bracknell) where residents have to pay for collection of their "green" waste, and the "collectors" just bung it into the (land-fill or for burning) ordinary collection truck. I'm not surprised you give no reference for that claim. In this era of fake news it's important to c...
by rurwin
Mon Feb 13, 2017 12:59 pm
Forum: General discussion
Topic: 12V Input to GPIO
Replies: 32
Views: 11265

Re: 12V Input to GPIO

I don't even know enough about wafer-scale semicondictors to be dangerous, but it seems perfectly possible to me to destroy a semiconductor junction simply by having an electric field across it. Sure that would probably involve charge carriers moving and hence current, but these things are tiny; it ...
by rurwin
Wed Feb 08, 2017 4:30 pm
Forum: General programming discussion
Topic: Which OS/Programming Language is best for my application?
Replies: 9
Views: 4033

Re: Which OS/Programming Language is best for my application

I would go with Raspbian and Python. That's well-tested with tons of support available. The only issue would be avoiding an untidy shutdown when the battery ran out and I would not be surprised if you still had that with Windows IoT.
by rurwin
Wed Feb 08, 2017 9:34 am
Forum: Beginners
Topic: Measuring strain on a bike frame
Replies: 5
Views: 1895

Re: Measuring strain on a bike frame

Strain gauages are not that easy to read. You will certainly need additional hardware and probably you should choose some that is designed specifically for strain gauages. The Raspberry Pi can read from I2C and SPI interfaces easily. You could look at this: https://learn.sparkfun.com/tutorials/load-...
by rurwin
Wed Feb 08, 2017 9:06 am
Forum: General discussion
Topic: "Full" Linux on Pi?
Replies: 69
Views: 12571

Re: "Full" Linux on Pi?

I reckoned with 4 cores it was unlikely anything would pre-empt the pigpio daemon (no gui or stuff like that on this pi). I run the really fast stuff as a pigpio script at a max of about 3,000 steps per second (actually 2 motors in 1/2 step mode), and it doesn't even seem to be notice. Max cpu on t...
by rurwin
Tue Feb 07, 2017 4:08 pm
Forum: General discussion
Topic: "Full" Linux on Pi?
Replies: 69
Views: 12571

Re: "Full" Linux on Pi?

Almost no thread is 100% CPU-bound. They all wait for something to happen even if it's a 1kHz timer. When that happens something else can run on the same core.
by rurwin
Tue Feb 07, 2017 3:26 pm
Forum: General discussion
Topic: "Full" Linux on Pi?
Replies: 69
Views: 12571

Re: "Full" Linux on Pi?

The trick would be getting the kernel and other threads off that core. The link shows how that is done. Locking the thread on one core doesn't achieve anything if any other threads can also use it. The pthreads stuff I saw was all about optimising the execution of a group of threads that shared memo...
by rurwin
Tue Feb 07, 2017 12:51 pm
Forum: General discussion
Topic: "Full" Linux on Pi?
Replies: 69
Views: 12571

Re: "Full" Linux on Pi?

So I was wondering about the multi-core thing. Presumably one can bind the bit-banging thread to a single core. Give it a high priority. Then it can sing as fast as as it likes without anything else getting in the way. I have not tried this yet. Anyone out there done so? Here's your starter for ten...
by rurwin
Tue Feb 07, 2017 11:32 am
Forum: General discussion
Topic: How to put Raspberry pi 3 USB in device mode
Replies: 2
Views: 708

Re: How to put Raspberry pi 3 USB in device mode

It is not possible with any version of the Pi B. It is possible with the Pi Zero and might be possible with the Pi A. The Ethernet chip provides the USB hub that feeds the two or four USB sockets. Because that chip is on the bus and between the sockets and the CPU, it means that the bus must always ...
by rurwin
Mon Feb 06, 2017 2:01 pm
Forum: General discussion
Topic: "Full" Linux on Pi?
Replies: 69
Views: 12571

Re: "Full" Linux on Pi?

Turing developed ACE after the war had ended. After designing the ACE but before it was built, Turing worked on the first Manchester computers, which were the first true (stored-program, electronic, digital) computers to run. EDVAC came a few months later and ACE upto two years later, IIRC. The man...
by rurwin
Mon Feb 06, 2017 8:31 am
Forum: General discussion
Topic: "Full" Linux on Pi?
Replies: 69
Views: 12571

Re: "Full" Linux on Pi?

The CDC Cyber series used 60-bit words: The central processor (CPU) and central memory (CM) operated in units of 60-bit words. In CDC lingo, the term "byte" referred to 12-bit entities (which coincided with the word size used by the peripheral processors). Characters were six bits, operation codes w...
by rurwin
Sun Feb 05, 2017 11:58 pm
Forum: General discussion
Topic: "Full" Linux on Pi?
Replies: 69
Views: 12571

Re: "Full" Linux on Pi?

We could use Base-32, but most of use can't remember the patterns and don't like handling five bits at a time. The first programmers on the Manchester Mark I programmed directly in Baudot code. See Alan Turing's manual for the Mark I here: http://curation.cs.manchester.ac.uk/computer50/www.computer...
by rurwin
Fri Feb 03, 2017 9:01 pm
Forum: General discussion
Topic: 12V Input to GPIO
Replies: 32
Views: 11265

Re: 12V Input to GPIO

So like this:
tmp.png
tmp.png (11.14 KiB) Viewed 9275 times
by rurwin
Fri Feb 03, 2017 9:34 am
Forum: General discussion
Topic: "Full" Linux on Pi?
Replies: 69
Views: 12571

Re: "Full" Linux on Pi?

It looks like LinuxCNC now provides native support for Xenomai. See: http://linuxcnc.org/docs/master/html/co ... #_realtime
by rurwin
Thu Feb 02, 2017 4:31 pm
Forum: General discussion
Topic: 12V Input to GPIO
Replies: 32
Views: 11265

Re: 12V Input to GPIO

If you know that your 12V signal is definitely either 12V or zero and it doesn't have any high voltage spikes on it, then you can use a simple voltage divider using a couple of resistors. However if you need to accept any voltage in a wide range then you need a more complex solution maybe including ...
by rurwin
Thu Feb 02, 2017 10:48 am
Forum: General discussion
Topic: "Full" Linux on Pi?
Replies: 69
Views: 12571

Re: "Full" Linux on Pi?

Almost certainly, it would be simple for an experienced programmer to convert LinuxCNC for the Pi. The Linux stuff is probably all there, only requiring a recompile of the kernel with some different flags, and the access to the parallel port is likely to be in one place and it is compatible with how...
by rurwin
Tue Jan 31, 2017 4:09 pm
Forum: General discussion
Topic: My 2 Cents: Coin Heatsink :)_
Replies: 34
Views: 12537

Re: My 2 Cents: Coin Heatsink :)_

Maybe someone else will do, the loctite is tighter then I thought :) When I was a young engineer there was me and my boss in one office. We had rotary phones and they slid around when you tried to dial, so I Blu-Tak'd mine down. My boss used my phone once and realised it didn't move, saw the bottle...
by rurwin
Tue Jan 31, 2017 11:21 am
Forum: Troubleshooting
Topic: RPI blown using NPN transistor.
Replies: 12
Views: 2260

Re: RPI blown using NPN transistor.

I did that calculation last night with my thirty-year-old recollection of transistor theory. V(BE) is 0.7V, making the voltage across the base resistor 2.4V I(B) is therefore 2.4/1000 = 2.4mA H(FE) is generally around 100, so I(CE) will attempt to be 240mA. That is not above the maximum current that...
by rurwin
Mon Jan 30, 2017 4:51 pm
Forum: Troubleshooting
Topic: RPI blown using NPN transistor.
Replies: 12
Views: 2260

Re: RPI blown using NPN transistor.

I think rpdom has it right. With the added possibility that the transistor fried in such a way that it shorted the collector with the base. The 240 ohm resistor is possibly not enough to prevent dangerous voltages getting to the Pi and it might have also burned short-circuit. A wise man once said "a...
by rurwin
Mon Jan 30, 2017 10:56 am
Forum: Python
Topic: Battery level indication
Replies: 8
Views: 4843

Re: Battery level indication

You would have to make some electronics and make modifications to the board of that power supply. Please only do that if you know how to do it and what you are doing since Lithium batteries can catch fire if short-circuited or damaged, and it's a nasty chemical-type fire that burns hot, emits toxic ...
by rurwin
Thu Jan 19, 2017 3:52 pm
Forum: HATs and other add-ons
Topic: how to sense 220v input -solved- I hope
Replies: 51
Views: 53170

Re: how to sense 220v input -solved- I hope

Whenever I use stripboard for mains I always remove at least one full track between live and neutral and I make sure to break the live and neutral tracks with wide gaps so that they are as short as I can reasonably make them. The low voltage stuff is in a different part of the board and those tracks...
by rurwin
Mon Jan 16, 2017 10:43 am
Forum: Interfacing (DSI, CSI, I2C, etc.)
Topic: Python serial port (UART) tutorial
Replies: 10
Views: 198180

Re: Python serial port (UART) tutorial

It is always dificult to handle binary data streams. Avoid them whenever possible even at the expense of doubling the amount of traffic. Because every byte value is valid in a binary stream, you cannot have a beginning and end marker to sync on. You can only have a byte count and go by luck and care...
by rurwin
Thu Jan 12, 2017 12:31 pm
Forum: General discussion
Topic: Selling The Raspberry Pi
Replies: 18
Views: 4097

Re: Selling The Raspberry Pi

I am only aware of three things that are installed by default on the Raspberry Pi and that, IIUC, you cannot sell on: The desktop photographs TinyVNC Mathematica It is trivial to easy to remove those from the image that you supply. However, this question is asking for an opinion of your legal positi...
by rurwin
Thu Jan 12, 2017 10:09 am
Forum: Beginners
Topic: configuring raspberry pi on windows 8
Replies: 3
Views: 711

Re: configuring raspberry pi on windows 8

what might be the problem and why does it happen after reboot? what i have done Your Raspberry Pi rebooted. In doing so it forgot everything it was doing (including the ssh server) and went back and initialized everything (including the network interface) and reloaded the operating system. Then all...

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