Reducing the beeps from the JBL amp

don't know if you're still up (I'm left coast, so just got home) I'll be in the chat room for a little while thinking about this.

Edit: Can't figure out how to get into chat. I'm logged in, but it still won't let me. Firefox issue?

 

Mike, this is a terrific work that you are doing!! I just don't have a digital oscilloscope at hand and you have uncovered many of the inside details I was looking for.
After testing many different scenarios and combinations I have decided that I would gladly give up the JBL amp (and even the steering wheel controls) just for the sake of a decent sound, it is hard to believe that such advanced piece of electronic engineering design delivers so poor sound quality. However, in an effort to prevent loosing the steering wheel controls, my idea would be to come up with a little box that can understand the bare minimum basic commands that only pertain to the amp in terms of signal amplitude, that is: volume, balance and fader, to modify the incoming fixed level audio signal. Then I would add a nice digital parametric EQ with digital programmable crossover. to take care of modeling the sound quality. This way the beeps will be inherently removed and so will be the JBL amp box.

Could you post some data samples for different volume settings? I am curious to see if the sound level is sent as an absolute or relative value? I would tend to think that the specific sound level (0-63) would be transmitted as an absolute number.
Also, could you post some samples of the data transmitted when you modify balance and fader?

As a side note, have you have the chance to verify my findings about the poor sound quality of the tweeters in front compared to the ones in the back?

Thanks !!! We are getting there...

 

Thanks Mike. This is very good information, gives me something to start with.

 

So did you decipher this using brute force with an oscilloscope, or did you have a decoder? If you had a decoder, what did you use, where did you get it, and how did you connect it?

 

hello Mike & Synergyguy & all the others
If I understood well , you should see on the AVC_lan bus some messages
from 440 to 110 telling
hello I am here
here are my settings regarding:
volume
balance
fader
bass
meeddle
trebble
So the mfd can show the absolute settings.
:roll:

 

hello Mike
yes the upd6708 is hard to find , but it is the only IC able to interface correctly with the AVC LAN (or his brother uPD72042).
What you did allows to create an AVC_LAN monitor.
I think it is possible to get this upd6708 on ANY device connected to an AVC_LAN,so maybe you could visit scrapyards for toyota cars :mrgreen:

 

Here's the data sheet on the chip:

http://www.necel.com/nesdis/image/U10680EJ2V0DS00.pdf

 

Maybe I'm just being naive here, but considering how objectionable many find this beep, doesn't anyone here know anyone within Toyota they can convince to making this a problem they'll solve for us?

Last week, I showed my prius to a Honda Insight owner, and she now wants one to replace her Insight. When I told my fiance, she asked if I pointed out the beep. She said it would have stopped her from buying the car.

 

Take a look in the "Knowledge Base" as there are directions there for eliminating the backup beeps. I was going to get rid of the beeps but decided to leave it as is.

 

<div class='quotetop'>QUOTE(brosnan\";p=\"79546)</div>

Brosnan, why do you say the upd6708 is incapable of monitoring all traffic?

 

Here is another idea that I would like to offer to see if someone could expand upon to see if it may be a viable idea. I would prefer to see someone develop a LAN translator with external amplifier to use in place of the JBL amplifier. If this is not possible consider this idea.

Disconnect the L-R audio inputs to the amplifier. In its place, insert an fixed frequency fixed level oscillator. Take the individual (Front and Rear Left/Right) outputs of the amplifier and send to a rectifier circuit to generate a Front Left, Front Right, Rear Left, Rear Right DC control voltage. Apply this voltage to 4 VCA elements (Prefer THAT VCA chips). Two VCA's get their (buffered) audio input from the head units left audio signal, two VCA's get their audio input from the head units (buffered) right audio signal. The 4 VCA's gain will be controlled from the amplifiers rectified DC voltage. When the system is panned center, equal gain is requested of all four VCA elements. As the pan and balance from the head unit is adjusted, the output DC voltages will follow, making the VCA elements follow the identical pan/balance image. Amplifier level increases and decreases including no signal (0ff) would be passed to the VCA elements as a DC voltage ranging from no signal (off) to max level. This output would be buffered to RCA outputs. The RCA outputs would be used to feed a external amplifier, never having been processed by the JBL amplifier.

In addition, a notch filter could be used to capture the nav tone output (I also suggest a simple gate circuit that would turn off when no tone is present) of the amplifier, with the signal summed to a post VCA position but with a trim pot or level control. We now have Pan, Balance, and level control as well as the nav tones (Possible idea - the nav audio output be permanently rewired to the center speaker) being controlled in this analog box with the JBL providing only the reference signal.

We could control the EQ in the same manner by adding 3 additional oscillator input frequencies and sending the amplifier outputs through notch filters and rectrifiers and then to a VCA controlled EQ circuit but instead it may make more sense to have an in line EQ feeding the input of this magic box.

This is just an off the wall idea for someone to expand on as it gives a pure analog solution to both signal path and signal control without moding the amplifier, but only messing with its input and output signals. (Adapter connectors that when removed reverts back to the stock installation)

Any further comments or ideas? I (we) would like to see something developed that would allow easy use of external amplifiers on the Prius. There is at least some market for such a product. As I mentioned at the top of the message, I would prefer a LAN based solution eliminating the JBL amp, but if not this may be a reasonable option.

 

Mike,

I worked a bit on this tonight. I will send you what I came up with.

 

Chuck, interesting concept. Probably would be easier designing our own AVC interpreter and then feeding its control to VCAs. Would need to find VCF though for analog based EQ.

What did you mean by nav tone? If you mean the nav lady speaking, that goes directly from NAV box straight to front driver woofer.

One possible problem with your concept though. When the MFD sends a beep request to the JVC amp, that would probably cause all your VCAs to max out during that period. I suppose though you could use a notch filter to detect that beep and hold the VCAs' control voltages during that time.

 

It's exciting seeing the work you all are putting into this...sounds like you're getting closer to reverse engineering the AVC-LAN protocol.

Just a thought -- has anybody contacted Toyota or one of the other partners in the AVC-LAN standard to see if technical specs on the protocol can be had or licensed? Since the push is to make this a standard comm protocol in the auto industry, they might be happy to share info for third party devices.

If we had a protocol spec, it wouldn't be too difficult to build an intermediate device to intercept and interpret the AVC-LAN signals from the screen/HU and control any number of external devices. Since reverse engineering the protocol is a matter of time and patience, there's little incentive for Toyota and partners to keep the information too tightly controlled.

I'll try to contact some folks and see if the spec is accessible or available to license...if the licensing cost is not too exorbitant, somebody might be interested in paying to build third party add-ons. Maybe the US patent application has some useful information...at least its available to the public.