Raspberry Pi

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Postby Viewmaster » Thu Oct 04, 2012 7:17 pm

To break out of the Raspberrypi here are all the General Purpose i/p o/p
connections together with C code on how to access all the pins directly.

http://elinux.org/Rpi_Low-level_peripherals

And for those who may thrive on eating Raspberry schematics see here...
http://www.raspberrypi.org/wp-content/u ... s-R1.0.pdf
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Postby dominicbeesley » Thu Oct 04, 2012 8:56 pm

Sorry Steve, got to diagree with you on the DONT USE IT message.

I got a couple of DDS-60 boards a while back and they are all SMD with quite a few chips. I have to say at first I was quite daunted but it was actually pretty easy to get good results. I would recommend doing all the work on a big piece of A3 and having a decent magnifier to hand though.

I think the small size is a selling point for these kits. One of the big whinges about the first boards for the RPI was that there were no mounting holes. I wish they'd thought the hardware through just a bit more and come up with specified mounting holes and headers so we could stack them like Arduino shields and mounted the sdcard so that it was over the back of the board instead of sticking out....
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Postby AncientBrit » Thu Oct 04, 2012 10:38 pm

Ah, Dominic, you've got age on your side.

Us oldies find surface mount just a tad too small,

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Postby Steve Anderson » Fri Oct 05, 2012 2:37 pm

dominicbeesley wrote:Sorry Steve, got to diagree with you on the DONT USE IT message....


Well, I have to concede that I have used SMD devices (SOICs) on veroboard, but it was a bodge. But when a chip has pins spaced at 0.5mm and there's upward of 60 of 'em it all gets a little too much.

I have seen kits where the major SMD devices have been soldered already, you do the rest. It's a reasonable compromise for kit construction where everything has been thought out beforehand.

My point was that someone is listening to user feedback and doing something about the issues.

A large (if not the largest) part of the cost of a kit of this nature is the PCB. You can change the software, you can change a resistor from 10k to 4k7, the cost impact is minimal. But to re-lay out the PCB could put you in deep water. What about the 5000 already made that are now useless? The losses can be enormous.

So Kudos to those that have made this change to this kit, if there were a choice between MkI and MkII, with a small increase in board area and even perhaps cost, I know which one I would choose. PCBs once within a production environment are costed on area and number of processes required.

In this plug-and-play world the fact that someone is producing kits that require assembly has to be encouraged. In an e-mail to Jeremy recently I said, "In a few years time anyone under the age of 35 will not know which end of a soldering iron gets hot."

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Postby dominicbeesley » Mon Oct 08, 2012 5:28 am

Back on topic...

Here's my first mini-project on the Raspberry to get my PI in as it were...

It's a little C program to exercise the sound card by outputting an NBTV test card. Now I've not tested this with a real televisor but I have scoped it and it looks to be outputting roughly what I'd expected and seems steady..

I can't get my 'visor out to try it but would be really grateful if one of you guys could give it a test. I've only tried it with Raspbian wheezy but it should theoretically work with other Linuxes as well so non Raspberry linux users could also give it a go.

To compile it, from a linux prompt:
Ensure you have the right sound packages installed
Code: Select all
sudo apt-get install libasound2

Download to a folder and get a terminal going and change to that folder
Unzip
Code: Select all
tar -xzf alsa-test-1.tar.gz

Change to the directory
Code: Select all
cd alsa-test-1

compile
Code: Select all
make

turn the sound all the way up on the soundcard
Code: Select all
amixer cset numid=1 -- 400

Run the test program
Code: Select all
./alsa-test-1


Press CTRL-C when you've had enough

Hopefully you should now get a simple set of grey-scale bars...
I have to say the sound output by mine is a bit noisy but I'm not sure if that isn't pick up from the Raspberry or from the usb power supply. There seems to be some odd ringing before and after the sync as if there is some kind of DSP trickery being done to the sound output.


D
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Postby gary » Sat Jan 26, 2013 6:18 pm

Ok tried it on my MUTR unit - seems to work OK - the contrast between bars is a bit difficult to pick up but they are there.

I attach as a benchmark the familiar Milligan clip also played out of the Pi via mplayer.

BTW the package to download for compilation is (at least on Rasbian):

sudo apt-get install libasound2-dev
Attachments
dompitest2(compressed).avi
Milligan
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dompitest(compressed 2).avi
Dom's Bars
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Perfecting an NBTV system is like trying to slam a revolving door...
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