Raspberry Pi

[Scrag Meister]

Are Pi cases compatible with A and B models?

or is there some difference with the port apertures or anything.

Edit : response from ModMyPi.com

The cases are interchangeable - however some cases such as the ModMyPi
cases and PiBows we're built to suit the Model B boards (so you will
have an extra hole where the LAN port is and a larger hole for the USB
ports).

The Cyntech cases we built with the Model A in mind, and have punch
out's to suit the A.

They all do fit however.

[Pondlife]

Some ideas featured in El Reg

Ten pi-fect projects for your new Raspberry Pi ? The Register

[Cliphead]

Some ideas featured in El Reg

Ten pi-fect projects for your new Raspberry Pi ? The Register

Did the FM transmitter project today and it works very well with the supplied wav file but the problem I have is with my own wav files. No matter how I convert them to mono playback is about half speed and pitch drops. I've checked sample and bit rate, the converted files play fine on any windows machine but on the Pi no joy.

If you've had a play with this are you seeing the same problem or have you successfully converted a file to mono or converted an mp3?

[d000hg]

As a non-electronics guy I was fascinated that the Pi "just happens" to transmit FM. How on earth does that work?

[Cliphead]

As a non-electronics guy I was fascinated that the Pi "just happens" to transmit FM. How on earth does that work?

Just about any computer or processor can do this. It's quick and dirty, illegal and will broadcast all sorts of harmonics that will interfere (over a short distance), with just about any transmitter / receiver. From the project site;

Modulation is done by adjusting the frequency using the fractional divider between 100.025Mhz and 99.975Mhz, which makes the audio signal. The fractional divider doesn't have enough resolution to produce more than ~6 bit audio, but since the PI is very fast, we can do oversampling to provide about 9.5 bit audio by using 128 subsamples per real audio sample.

Linky

Was fun listening to my 'radio station' on the car radio at the other end of the driveway (about 100m away).

[RSoles]

Well, seein' as it's yersel' ( and it's tipping down sleet outside)

I had a go at this, and my wav files play fine.


I'm using an Ubuntu 12.04 box for the wav file processing.
I had a copy of Beethoven's fifth ( OK not the best of choices) which had been
ripped from CD using Rhythmbox to give me a wav file with the following properties:-

Codec - Uncompressed 16-bit PCM audio
Channels - Stereo
Sample rate- 44100 Hz
Bitrate - N/A

I then used Audacity to change this to match the supplied wav file:-

Codec - Uncompressed 16-bit PCM audio
Channels - Mono
Sample rate- 22050 Hz
Bitrate - N/A


Set up the Pi, and ran it. The difficult part was finding an fm radio.
Ended up using the digital FM tuner on my 'phone.

All was well with both the supplied Starwars theme and my ripped Beethoven.


A funny incident occurred while running this; I'd temporarily switched my phone radio off
to save the battery and on turning it back on there was Beethoven.
Oops, ran to the pi and did several ^C s. Still Beethoven. Then pulled the power on pi.
Still Beethoven. Smelled rat. Checked radio. Set to radio three.

By sheer coincidence they were playing the same track. What are the odds against that?

[Cliphead]

I then used Audacity to change this to match the supplied wav file:-

Codec - Uncompressed 16-bit PCM audio
Channels - Mono
Sample rate- 22050 Hz
Bitrate - N/A

Doing exactly the same many times over and the Pi still plays the files slowly

A funny incident occurred while running this; I'd temporarily switched my phone radio off
to save the battery and on turning it back on there was Beethoven.
Oops, ran to the pi and did several ^C s. Still Beethoven. Then pulled the power on pi.
Still Beethoven. Smelled rat. Checked radio. Set to radio three.

By sheer coincidence they were playing the same track. What are the odds against that?

Quite a coincidence

The Pi continues to broadcast anyway after playing a file, gotta pull the power to stop it.

[RSoles]

The Pi continues to broadcast anyway after playing a file, gotta pull the power to stop it.

Now that's interesting, mine stopped immediately I killed the process with ^C.

I was running the program directly, using the line:-
sudo ./pifm sample.wav 105.0

You have a pm BTW.

Sorry, would have been back sooner, been watching arduino/zigbee videos.

[Cliphead]

Now that's interesting, mine stopped immediately I killed the process with ^C.

I was running the program directly, using the line:-
sudo ./pifm sample.wav 105.0

You have a pm BTW.

Sorry, would have been back sooner, been watching arduino/zigbee videos.

Running the program directly as well although as root. I'll be back at it again when the rugby finishes.

[SupremeSpod]

It's quite surprising just how fast the Pi really is.

I've been playing around with some code that accesses the "Linux FrameBuffer" directly and implemented good old Bresenhams Line Drawing, Circle Drawing algorithm's in "C" and it shifts like the proverbial.

The good old ARM is very good at integer arithmetic (The absence of a "divide" is a bit of a bastard but if you can avoid any division other than ^2 then no real problems).