Member Since: 10 Aug 2014
Location: Oslo
Posts: 12
Wireless and fully digital audio playback from phone
So the entertainment system system on the d3 is great - well it is in a Land Rover so it fails all the time in new and interesting ways, as one would expect - but for a car stereo system the sound quality is quite good. But the problem at hand is how to stream high quality audio INTO the head unit of the radio from an external source i.e. a iPhone or Android device.
With phones now sending high quality pulse-width modulated (PWM) audio signals over bluetooth, it is a surprising that the only way to connect an external sound source to the radio is through the analog AUX port behind the center console. Noticing the difference from CD playback, the AUX input is clearly not doing justice to the high quality downstream components that the fine people at Solihull equipped this car with. For some reason there is no way to input audio digitally to the head unit. Must have been the wrong kind of bean counter attending a design meeting…
I guess that adding a digital interface to the radio head unit would solve that. With this in place, an ordinary bluetooth to SPDIF adapter could be used to properly transfer high quality digital music signal from a phone. I2S or SPDIF in either coax or Toslink fiber config would be good I guess. SPDIF being the standard external audio interconnect between consumer audio devices. I2S on the other hand is the standard internal audio interconnect between integrated circuits on a circuit board. Not written in stone, but that is the basic difference.
When you pop the lid off the radio, you’ll notice that the chip employed for digital signal processing (DSP) is the very capable Philips SAA7706H (image below, low right under the MOST bus cable). It actually has both SPDIF and I2S inputs. The SAA7706H is programmed over the I2C bus, but hopefully no programming would be necessary - hopefully we would be able to just piggyback on existing signals found in the rough.
Note the block diagram on page 6 and the application circuit diagram on page 45.
The SPDIF inputs are on pins 24 and 25 (dual inputs actually). Pin 25 is connected to a capacitor and then to ground from what I can see - usually meaning it is not connected (could also be connected to the MOST bus receiver, did not measure it out)… I would imagine adding an electrical input circuit would consist of drilling a hole in the lid, popping in a RCA SPIDIF coax connector, add two capacitors and a resistor as a DC offset buffer and low pass filter circuits, and input it to pin 24 or 25 - as described in the application circuit diagram on page 45. Alternatively a Toslink connector if fiber is a more useful format. From reading the block diagram on page 6 in the data sheet, I get a feeling that the SPDIF input is just mixed into the I2S signal before the second DSP...?
Using the I2S inputs is another approach. The I2S inputs are on pins 27, 28 and 29. In the the case of I2S integration, one would also need a SPDIF to I2S conversion circuit like this one http://www.pavouk.org/hw/modulardac/en_cs8416spdif.html , or utilise a Raspberry PI which has I2S outputs available.
Alternatively, I assume the input ribbon cable from the CD changer is also I2S bus based in this day and age... Maybe one could hook up to those connectors? In the case of CD ribbon "integration", one would select CD for listening to the digital SPDIF input.
Would this be possible? Any thoughts or experiences?
Brgds Karsten
Last edited by karsteb on 20th Mar 2019 7:09 pm. Edited 1 time in total
7th Feb 2017 10:39 pm
kk7408
Member Since: 29 Apr 2011
Location: Lancashire
Posts: 61
Wow...too technical for me!
However, I would love to be able to do the same....Having to connect the aux to headphone output works, but it seems like the sound would be much betterD3 HSE
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Lancia Delta Integrale Evo
19th Feb 2017 10:42 am
geoffsnook
Member Since: 13 Jun 2014
Location: south wales
Posts: 3170
Over my head as well but it would be good if it were to work Discovery 3 se gone
Range rover sport supercharged here:)
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They just make the best of everything they have.
19th Feb 2017 12:57 pm
JackNorris
Member Since: 06 Jul 2012
Location: Beds/Bucks Border
Posts: 1879
I'd say you've clearly got knowledge in this and it sounds plausible but I haven't a clue. I'd say give it a go or maybe wiggs or Robbie may know.MY2023 Discovery 5 R-Dynamic 3.0
MY2020 Discovery 5 Landmark 3.0 - SOLD
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19th Feb 2017 1:08 pm
Asa
Member Since: 03 Jul 2016
Location: Essex
Posts: 178
streaming music
I use a unit made by Pure. the digital radio specialists and is called the Highway 600 it connects via an FM frequency to the head unit of my D3 HSE and delivers top quality audio transfer from my iphone 4s.
All functions of my phone are available via this unit and the microphone provided for hands free is crystal clear.
It also functions as a DAB radio which is as good as the signal you can receive! Either superb or patchy!
It took about an hour to fit by me and that was mainly dismantling trim to hide the wires. it only uses a couple of AA batteries so no live connections needed.
A USB plug connection is provided to enable power for the Antenna which is discreetly mounted on the front screen, not where PURE suggesbut out of sight behind the drivers side Sun Visor.
Only a small control unit is visible or could be mounted anywhere, leave it set to bluetooth music and it automatically connects to your phone when the ignition turns on, this is because the ignition circuit ignites the auxillary power socket for the new Antenna!
It cost £149.
I only wanted to listen to quality music from my phone, for that alone it's brilliant.
19th Feb 2017 4:23 pm
Discoveringcomfort
Member Since: 16 Sep 2015
Location: Berkshire
Posts: 637
Alternatively a Toslink connector if fiber is a more useful format.
The Logic 7 amp has an unused digital optical connector on it, has anyone tried using it?Series 1 V8
Series 2 Hibrid V8
Discovery 3 HSE V8
19th Feb 2017 4:35 pm
karsteb
Member Since: 10 Aug 2014
Location: Oslo
Posts: 12
Got a PM from Jewls on the subject, which sent me down this rabbit hole again...
From the block diagram of the Digital Signal Processor (DSP) http://www.key-chips.com/p-1458183.pdf page 6, it seems the cd player is actually transmitting its audio to the DSP over an i2s bus.
Then, while browsing for some other amp stuff, I found this $25 bluetooth module, which transmits the audio on a i2s bus, the Tinysine TSA7010 https://www.tinyosshop.com/tsa7010
On the picture above you'll see two headphone jacks, but will not be using them. The interesting bits here are the pins labeled i2s. Maybe it would be possible to just add the two or three i2s wires from TSA7010 into the i2s pins on the DSP and get sound that way? Or maybe splice the TSA7010 into the ribbon cable that comes from the CD player (upper left on the picture of the head unit) and have the head unit think it is getting its audio data from the CD player...
Last edited by karsteb on 25th Apr 2019 5:19 pm. Edited 2 times in total
20th Mar 2019 7:55 pm
John Andre Ognheim
Member Since: 29 Oct 2013
Location: Bergen
Posts: 111
Following
Interresting.
Hows going with this project?
Could it be possible to link that BT unit in as the "CD" player, so u could use the stering wheel buttons to control it. next song etc...
I`ve often been thinking, it should be possible to disconnect the buit in cd changer, and get a " emulator" to fool the radio, to still see the CD player.
But my electronic insight stops there.....
Just want to have an affordable BT unit, that can be controlled by the steering wheel, and ofcourse sound through the HK system....
Like the moBridge BT unit... thats to xpensive i think.D3, MY06
25th Apr 2019 12:13 am
karsteb
Member Since: 10 Aug 2014
Location: Oslo
Posts: 12
Not much traction currently, but would like to get to it sometime. I have seen BT controllers that can link to buttons, so I guess it can be done...
I also agree that the mObridge is very nice, but as you said it is a little expensive for what it is. Also they operate directly on the MOST optical bus and I cannot find any "open source" or inexpensive way to connect to the MOST bus, but the i2s bus is readily available in a lot of equipment.
Also there is the problem that it seems the MOST bus concept has not got that much adoption in the industry. The idea with optical is good, but they chose a linked bus topology, which from a stability standpoint is a really bad idea - as the computer industry discovered in the early 90´s and replaced 10BASE2 with ethernet which has a hub and spoke topology... Well - the auto industry...
In the post above I mixed up i2s and i2c buses. i2s is the audio bus and i2c is a general purpose bus for interboard communication - both are used here. Corrected it, and added some links.
25th Apr 2019 5:44 pm
vjuntura
Member Since: 28 Mar 2019
Location: Oulu
Posts: 20
One thing that I'm wondering is that there is also analog inputs for CD described in the block diagrams in the datasheet. I was thinking that what if I2S is only used for controlling the CD changer and/or for example transmitting the information about audio tracks etc?
I could measure the analod inputs of the chip while playing music from CD with oscilloscope. If there is nothing in the analog inputs, then sound from CD is definitely transmitted via I2S and then we should be able to use that bus for our own applications. I2S bus can also be measured easily with a logic analysator.
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and it sounds plausible but I haven't a clue. I'd say give it a go or maybe wiggs or Robbie may know.
