Wireless digital audio transmission.
I used Nordic Semiconductor's NRF24L01 as wireless communication systems, they operate in the 2.4GHz band. Audio is compressed to MPEG1 layer3 format.
Transmitter:
It was built on the AT91SAM7S64 microcontroller.
As the transmission speed of NRF24L01 is about 400kbps (with acknowledgment and error correction), the LAME MP3 Encoder was used as the audio encoder. Bitrate set to 320kbps. Compression is done on the computer. As an output module for PulseAudio has been written, all sounds from the system can be redirected to the wireless speakers. You can also adjust the buffering delay.
The transmitter is seen by the system as a serial port / dev / ttyUSBx
Receiver:
Procek is AT91SAM7S512 (decoder requires a lot of ram), Helix decoder, I used TDA1543 as DAC.
Scheme:
Range:
Works through the wall, diagonally across the load-bearing wall between the floors, with the appropriate antenna arrangement.
Here is a test version of the transmitter in micro size:
A reprogrammed Logitech Unifying receiver was used.
Unfortunately, I didn't manage to squeeze high speed out of it, so its bitrate is only 128kbps. The range is also correspondingly smaller.
You might ask "Why not A2DP?".
I know from my own experience that A2DP is not very stable, LAME also has better sound quality.
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================== UPDATE 31.08.2010 =====================
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Photos of the newer version with the DAC CS4344:
Here is a comparison of the dimensions with the older one with an external DAC:
The transmitter is a reprogrammed Logitech Unifying with an antenna added:
PulseAudio screen:
The newer version has the ability to measure the supply voltage.
Power consumption:
~ 60mA during playback
~ 14mA while waiting for transmission
Available on the connector are: I / O, PWMy, RS, I2C, LEDs, USB.
Instead of the audio jack, you can mount the standard 4x goldpin.
Receiver diagram:
piotr_go wrote 2835 posts with
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Comments
I'm impressed :D I like :D full professionalism! Well done :) and what range of such a gem ?? how many meters in the open space ?? [Read more]
9m, I still did not check. I also checked whether it would break through 2 floors. When I set the antennas properly, it worked. [Read more]
and what are the costs of implementation? [Read more]
Prototype? Don't even ask. With a few pieces, it will probably be PLN 150-200 per set. [Read more]
I've always wanted to build something like this. I will ask why so expensive in the sense of what raises the price the most? and is it planned to go into production? ;) Because I would like to buy... [Read more]
What drives the price up the most is the fact that you have to buy items in several stores. To get some of them you have to do some research. So far I have not been able to find a suitable RP-SMA connector,... [Read more]
I am most interested in the set with a micro transmitter ;) Is it possible to replace the SMA connector with a fixed antenna or with another type of this connector - in the case of a device, such as an... [Read more]
You write that the whole thing works on 2.4GHz, hmm interesting ... It does not interfere with Wifi? For example, I would like to put it in an amplifier, and I keep a router on the amplifier, how will... [Read more]
Still regarding this price. I recommend looking for the price of the "SAM7-nRF24-64" Olimex kit. Similar structure, but no signals from Prock are available. A transmitter would be fine. Micro transmitter,... [Read more]
I missed that in the description:] Thanks. [Read more]
I can buy AT91SAM7S64B-AU for PLN 23, AT91SAM7S512 for PLN 40 ... design and making tiles for this is probably not a bigger problem, unless there is a top-down order to use double-sided boards. The problem... [Read more]
NRF24L01 is available from farnell.com [Read more]
On one-sided it is better not to do this, the manufacturer of the NRF does not recommend it. Added after 5 [minutes]: @ Mat_91 And they sell single pieces to ordinary mortals without foreign... [Read more]
piotr_go you still write that you have not found the right sma connector and that you have been up to something with the pin inside. Whether the connector you are looking for is not something like that... [Read more]
They do not sell, but I had the opportunity to buy from them through a friend. Payment by credit card only and charged in British pounds. [Read more]
@ Mat_91 These are a bit too big, it needs something edge-on, in SparkFun they have but I am not happy to pay several times more for a transfer and shipping as for connectors. [Read more]
I could use a nice gadget to make sound 4.0 with computer speakers and you used my favorite movie for the presentation [Read more]
A very interesting structure. Have you made any radio measurements? (network analyzer, spectrum analyzer) How did you choose the elements in the radio path? [Read more]
Wow nice design. I wonder how latency is there. Can't see lag in videos between audio and video? After all, it has to go through these compressions and decoders. I mean when you don't regulate... [Read more]