ELEKTOR FORUMS

Hi guys

Anyone looking at this project yet ... or anyone from Elektor planning for future enhancements ?

I'm really excited about it but I need to know if it is going to be able to receive and decode the bulk of UK internet radio stations which means it will need to do something with Real Audio (used by BBC etc).

Please .... if you have any ideas, let me know ....

Paul.

Harald Kipp, author/designer of the EIR replies
I will definitely look into the AlienBBC Code and once again into MPlayer. However, you should note, that we have quite specific license problems. All code must be compatible with the BSDL. GPL is a no no.

There are several reasons for this, most notably that Nut/OS is statically linked to the application code.

More infos at
http://www.freebsd.org/doc/en/articles/bsdl-gpl/article.html

Best regards,

Harald Kipp

We had similar issues with the WDR, a public local broadcaster with 5 main channels. Many people, including me, sent emails or called them to get explained, why they stick with the proprietary Realaudio format. Luckily, since the beginning of this year, all 5 channels are available via SHOUTcast. Next step will be to get them to Ogg Vorbis. But I agree, that old mother BBC may be less flexible (should I say undemocratically?).

Taking license issues seriously in general does not mean, that we have to think square. Actually using MP3 in Open Source project isn't completely free of risks.
http://www.theregister.co.uk/2001/06/26/mp3_owners_get_stroppy/
(When using VLSI chips, MP3 license had been paid by the manufacturer. This doesn't apply to AAC+ and WMA. Please check the VS1053 data sheet.)

I'm not able to make any promises right now, other than to look into this and trying to find a solution.

Regards,

Harald

P.S.: Immediately after the article was published, I checked this forum several times, but no threads about the EIR appeared. Discovered it yesterday by mere chance.

I assume, that you are not talking about the label, but conformance.

First, bare circuit boards cannot be CE compliant by their own. Almost all of them will fail ESD testing, at least. Nevertheless, for a working device you provide instructions about how to provide conformity. For the testing lab we use a specific enclosure, which may serve as a sample for the customer. Actually this doesn't really help, except to ensure the customer, that the device is generally compliant when following the same specific setup. In reality, the customer will use the board in a different environment and testing had to be done for this one. You cannot combine parts with CE marks and simply declare the final product CE compliant without further testing the combination.

The radio, however, will not work without soldering at least the power supply connector. Thus, the hobbyist builds the working device for his private use, which doesn't require CE testing. The other case is the engineer, who uses a device in a lab environment. He won't need CE compliance testing when fulfilling certain requirements.

Well, it's some time ago I studied all this CE stuff, so I may be wrong.

Sorry for the late response.

I agree, that it is quite tricky today to build a microcontroller board, which doesn't radiate. Quite often we had to visit the lab more than once to get a board through. Depending on the requirements, this costs about 1000 to 5000 USD.

I agree, that you don't need expensive equipment. But how much is much? Without the lab and their calibrated equipment it is difficult to make a decision. Of course we do some pre-compliance testing with our "cheap" Hameg spectrum analyzer and near field probes, but that doesn't fully avoid surprises in the lab. My experience is, that if you go to two different labs, you will get two different results. All this is still black magic somehow, as there are too many parameters involved.

To answer your actual question: Yes, we take extra care for EMI, because sooner or later all our boards will be tested in a lab. Just now I can't provide any EN numbers, which the board will fulfill. It is a four layer board with ground split analog and digital planes. The routing had been done with return paths in mind and avoids large loops at high frequency traces. We used more than 50 bypass caps and a ferrite bead for the noisy RS232 level shifter to keep the supply quiet. In the initial version, the one on the Elektor cover, we had even more inductors, but the pre-compliance test showed no advantage and they had been removed. (Btw. sometimes a 100 Ohm resistor helps more than a ferrites.)

In most cases external cables are responsible for radiated EMI. Therefore there are RC filters on all interfaces and the power supply connector is additionally protected by a common mode choke. Regarding ESD: All interfaces are protected by diodes. However, this does not apply to the JTAG interface and the expansion connectors. So please take pre-cautions when touching the bare board.

As far as I can say from my own experience, you can do a lot by following EMI design considerations, but you can never avoid to bring your product to a professional lab. The tests are costly, because they are time consuming. As long as you do not have your own equipment, you can talk to them to do a pre-compliance test first. This may take one or two hours only and costs just a few hundred dollars. You will get an EMI plot, which you can use to track down any problem with some low cost equipment.