Raspberry Pi Forums

mirojr

Yes thanks. I have been totally side tracked trying to hook up this scratch python thing. So I haven't got round to it yet.
Cheers

mirojr

Thanks

I will try this.

mirojr

Finally got the thing to work in its absolute basic form. Its a Kernighan type HelloWorld GPIO at best. I might post it with the scratch interface showing as well, because for novice like myself was a bit tricky finding out how to do very basic broadcast. Thanks Gerhard and Thomas Preston https://gi...

mirojr

Great that Gerhard

Many thanks for your help

mirojr

Hello, tried some things in python3, and think that something like the following snippet will solve the problem: cmd = 'broadcast hello' # # the length is the number of bytes in the message, not the number of characters. # n = len(bytes( cmd, 'UTF-8')) a = array('b') # convert len to the first four...

mirojr

Well signed char should I say, for b

mirojr

Ok got it.

Typecode.

Char

mirojr

Ok thanks Closest I got for my output was: b'\x00\x00\x00\x10'broadcast"hello" from using def sendCMD(cmd): n = len(cmd) a = [] a.append((n >> 24) & 0xFF) a.append((n >> 16) & 0xFF) a.append((n >> 8) & 0xFF) a.append(n & 0xFF) b = '' for i in list(range(len(a))): b += str(a...

mirojr

Thanks

I will look at this code.

will look how python 3 is handles its 4 byte buffer. It seems that the encoding on 2.7 is much more straight forward. Especially how it concatenates it all.

mirojr

Ok the 4 bytes I get now.

I appends this to the beginning of the string, they are hex values of bytes when displayed, but cast to strings I think

the version in python 3 doesn't perform this well.

Anyway I will keep looking

mirojr

Thanks

It looks like your code is for use with python 2.7

I am still wondering why the version 3 code doesn't actually work.

I am going to keep looking.

Just trying to understand this 4 byte section yet!

mirojr

agreed! exactly what I felt when reading it.

mirojr

Thanks I am actually after getting an understanding of the mesh python handling. Not many tutorials. Am having to root through code and try and figure it out. But I suppose that's the best way to learn. Its mainly the scratch side that's seems harder. The passing of the strings etc. I am trying to g...

mirojr

Ok cheers

The ocr pdf
http://www.ocr.org.uk/Images/129940-rec ... lights.pdf

states pin 17 as ground

mirojr

Hi Just trying to find out why the GPIO pins 17,20,25 are ground connections in this circuit http://www.ocr.org.uk/Images/129940-recipe-card-traffic-lights.pdf They are labelled as DNC on this pinout diagram do not connect http://www.hobbytronics.co.uk/image/data/tutorial/raspberry-pi/gpio-pinout.jp...

mirojr

hi I am looking for a simple example to get me started connecting python to scratch using mesh. I used the examples from http://wiki.scratch.mit.edu/wiki/Communicating_to_Scratch_via_Python_3.x I have python 2.7 and 3.3 The example initially didn't work due to b += a[i] TypeError: Can't convert 'int...

mirojr

Is there anyone who could outline the bootcode.bin start.elf and kernel.img but in the context of older 8 bit systems?

Things were complicated with 8 bit systems, but now its very complicated.

Does the bootcode.bin act as a bios with an instruction set similar to ARM?

Thanks

mirojr

I booted into rasbian copied my bootcode.bin and start.elf onto the SD card along with my kernel.img and it all worked.
So thanks for that.

mirojr

Seems the Baking Pi tutorial doesn't really mention the files I need

Bit of a non-starter for me that

mirojr

Thanks David The noobs card didn't have a kernel.img image, just some recovery images. It was as if it had not uncompressed into the selected OS or something. If I look at /boot whilst in raspbian I can see the files as expected, but not while the card is in my laptop. Anyway I will try another SD c...

mirojr

Hi My first question is do I need to format my SD card before adding the kernel.img? Or can I add the kernel.img file to any sd card and boot from that? My current SD card has noobs and that has no kernel.img to rename. I tried just adding the kernel.img but I think it boots slightly differently tha...

mirojr

So I can exclude the optocoupler or is this better to have Genuine question, I don't know, but aren't they used because 1) you want no electrical connections between two systems, or 2) you want to prevent the possibility of dangerous voltages entering a system I don't think either applies in your c...

mirojr

So I can exclude the optocoupler or is this better to have

mirojr

Thanks. That's good. (and I think I bought a Darlington array a few days ago)

That aside if I needed the relay circuit is there a minimum circuit for the gpio on the pi?

mirojr

Thanks for the input. It looks like I will need a relay as the transistor as an amplifier doesn't look like it will cut it, although I do not have the spec for the bulb to be sure, but I know a little battery power would definitely work. Rather than use my piface with its relays I am going to create...

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