[jediknight0]

OK, can someone explain this to me:

I have an iPhone 3G that I want to hook up to my head unit through the back AUX/CDC port. I also have a working car charger that takes 12V in and has a USB port for charging that works with the iPhone.

NOTE: For the record, the charger outputs 5V, 2.8V, 2.0V and GND on the USB pins.

I hook up the left/right/gnd audio pins in the dock connector to the audio pins on the head unit. I also hook up pins 11/15/16 to pin 21 through a 66K ohm resistor (actually two 33K in series). Everything works great, no "not designed for iphone message".

I hook up the USB pins in the dock connector to the car charger and the power for the charger to the 12V/GND lines in the AUX/CDC port of the head unit. The phone charges, but I only have left audio. The right audio is instead various electrical noise - not noise on top of the audio, just noise. I unplug power from the car charger without unpluging anything else and immediately I have left and right audio again.

Also wierd is when the USB charger is attached, about every 4th or 5th time I attach the connector to the iPhone I get a "this device is not compatible with the iPhone" message - but it's a slightly different message than I used to see.

Any ideas?

 

[Juaquin]

Is it possible some of your wires are touching inside the connector? It seems like maybe one of the USB pins is touching that audio channel, resulting in it overpowering whatever audio was coming through that channel with noise.

 

[jediknight0]

Quote:

Originally Posted by Juaquin /img/forum/go_quote.gif Is it possible some of your wires are touching inside the connector? It seems like maybe one of the USB pins is touching that audio channel, resulting in it overpowering whatever audio was coming through that channel with noise.

Unlikely. At the dock connector, audio is pins 2/3/4 while USB is pins 16/23/25/27 at the other end of the connector. On the other end of the cable the pins are definately not touching.

I'm wondering if the 66K ohm resistor could have something to do with it? Maybe if I replaced that resistor with one of the more commonly used values it would work right (but have the "not for iPhone message). The only problem is that soldering on the connector is so tough that if I try and re-solder anything I'm pretty sure the connector will get destroyed.

 

[AnalogArsonist]

Juaquin is right about the noise. It sounds like the right channel is shorting to something, like shorting a speaker with a 9V battery. Did you disconnect the entire USB connector or just the 5V rail when right channel starts working? Recheck all your connections and make sure you know for a fact which side pin 1 is on. Also, there are no "commonly used values" for the iphone (hence the last half of this thread). All that "commonly used" information you will find is based on the old IPODs and the associated peripherals. There are no "made for the iphone" products out yet. You can modify them to get them working by floating pin 21 but that's it. The 66k is why you aren't getting the "not made for iphone" message, at least the first four times..

 

[jediknight0]

I've triple-checked all my connections and can't find anything shorting, but it's hard to check at the dock connector itself due to the size.

Here's the setup - the left/right/gnd audio pins (2/3/4) are connected to the left/right/gnd audio pins on the back of my head unit. Pins 11/15/16 are shorted together. Those pins are connected through the 66K resistor to pin 21. The combination of 11/15/16 (consider it one pin now) and pins 23/25/27 (the USB pins) are connected to a USB connector. That USB connector is pluged into a car charger and the power for that charger (12V/GND) is connected to the 12V/GND (not audio GND) lines at the back of the head unit.

Using the cable like this I only get left audio and right noise. If I unplug the 12V/GND to the car charger, I get left/right audio.

I just don't see how in the worst possible case I could be shorting anything except maybe pin 1 (also a GND of some sort), but I my multimeter says I'm not...

 

[AnalogArsonist]

Is your charger stepping down the voltage to 5V or does it go into the phone as 12V straight from your wire harness? Does the phone go into charging mode with the line-out hooked up?

 

[hartphoto]

I'm thinking of doing a conversion of a XtremeMac 'Incharge Auto' charger XtremeMac InCharge Auto, Black to also have the line out in a separate cable. The charger works great, no 'This accessory' message.

What I was thinking is to copy the pinout they have for the charger feature, but just add in (with a new connector) a LOD feature.

Then, I'll have a split connector out of my iPhone 3g. One for charging, one for LOD.

The cable on the Incharge is so long, I'll use part of it to make my LOD cable, and everything will 'match'.

Workable?

 

[Juaquin]

jedi, do you have a multimeter with a connection test (where it will create a tone if the two terminals create a circuit)? This would make it really easy to test if various pins are touching - just put one lead on each pin (from wherever you can access the pin, top or bottom or even leads to them) and if it beeps, we have a problem.

Other than that I'm not sure why only one channel would be affected like this. Maybe that channels wire accidentally came in contact with a shield on a cable, and at some point that shield is hitting something on the USB power circuit? I'm just guessing here.

 

[Ludi]

Hi,

I just tried my board with the 66kOhm resistor. It seams to work quite well. I only received the popup message (not designed for the iPhone) once from about 20 tests.

I am able to charge the iPhone, the line out works very good (left and right) and I can send commands over the serial interface.

BUT!!!
I am still not able to make a phone call over the line out! Does anyone have any further ideas?

Thanks
Ludi

 

[wigging]

I am still getting the accessory warning when I plug in my line out cable to my iPhone 3G. I'm using a 66.5 kOhm resistor from Digikey (part no. 66.5KXBK-ND) between pins 21 and 30 (GND). I am also connecting pin 11 to pin 30 (GND). Does the resistance need to be exactly 66 kOhm and do I need to connect all the ground pins to eachother? Any help would be appreciated.

 

[AnalogArsonist]

Wigging: mine was exactly 66kohm just because that was the sum of what I had available. According to the dock, it is 357k in parallel with 82.5k + the channel resistance of the IC. Do you have a potentiometer you could play with? Ideally, the best way to get the resistance value would be to plug the phone into the dock and then measure pin21 to GND. Mine was broken so I couldn't do it. BTW, Digikey has a resistor kit that is inexpensive.

Ludi: I'm glad it kind of works. The value must have to be very accurate or we're missing something. Do you have to be jailbroken to play with RS232 (so much potential)? With regard to the phone call over line out, could you be more specific as to what it's not doing? Does the audio start coming from the phone speaker? It might not be possible...

 

[Ludi]

Today I connected the iPhone to my own car adapter several times. I receive the message unsteady (about every 10 try).
If the iPhone is unlocked (the screen) the message does not appear, but if the iPhone is locked (press power button) I receive the message sometimes. Maybe the resistor with 66k is not the right one.

For using the RS232 the iPhone needs to be jailbroken, but I use only the standard calls from the iPod functions, therefore this is not necessary. Now I can use my steering wheel (car) radio buttons to jump to the next song and so on. That works fine!

I connected the line out from the phone to the line in from my car radio. For example if I hear music (iPod functions) and than receive a phone call you can hear the ring ton over the car speakers. But If I accept the call the speech switches to the iPhone speakers! If possible I would like to hear the phone call over the car speakers as well.

 

[jediknight0]

For the record, I've solved my problem of noisey left-only audio when charging - I was being an idiot. I didn't short any lines at all, but I swapped the audio ground and right audio lines. Once I built a new cable I saw the problem and corrected it, the problem went away.

Thanks to everyone for the help.

Oh, and I can confirm that using a 66K resistor (actually two 33K resistors in series) or a single 68K resistor I don't ever have the "not for iPhone" message. It seems very solid and consistent for me.

This 66K-68K info is great - I think this is the only forum online that has that info. Everyone else seems to still be in the dark about the iPhone 3G.

 

[ridax]

.

 

[hartphoto]

Quote:

Originally Posted by ridax /img/forum/go_quote.gif .

Considering the price of admission into the 'Made for iPhone/iPod' program, I'm betting the same.

Good thing the subscription service worked before you edited your post