Anonymous
19th January 2003, 03:21 PM
This message contains all postings in this thread
dated before January 19th 2003
Subject: Car kit creation issues
From: Carlos
Date: 24 Dec, 2002 22:09:25
So I'm in the process of making a full car kit for the XDA. My
goal is to provide power, serial (for GPS), and sound in/out.
I've conquered the physical part by hacking up a cradle, which
will be mounted in the car. That was more complex than it
seems. Not particularly complicated, but required work.
For the electronics, "plan A" was to simply wire the output to
the car radio and attach a standard microphone for input.
However, it appears that the microphone input requires a high
level signal. I did not get any input at all from a microphone
(yes, tested more than one). I was only able to get input by
connecting another audio device's headphone connector directly
to pin 1/Mic In, and then it wasn't as loud as I would have
expected.
Also, the sound ouput via the bottom connector is quite tinny
and faint compared to the headset output. At least, it is when
listening via headphones; maybe headphones are too low-impedance
for that output.
Hmm, ok, it does seem to be an impedance issue. When I ran that
output to a cassette adapter it sounded fine, and actually
louder than the cassette adapter plugged into the headset jack.
Ok, that's good.
So I tried "plan B"--connecting it to an existing Ericsson car
kit. However, the Ericsson's kit's electronics apparently come
from the Bizarro world. I was unable to figure out how a phone
tells the kit that there is a call and to activate itself.
There are two wires fron the Ericsson unit which do this, but
nothing seems to change with them. They keep the same voltage
and resistance whether a call is on or not. Weird.
Plan C...the only other thing I can think of is to get a
microphone to boost the input. I hesitate doing this because
I'm thinking that echo will be a problem, which is why I was
considering using the Ericsson kit anyway--excellent noise
cancellation. It appears that even a universal kit would be
unusable with this device because I don't believe they boost the
microphone at all.
Anybody got other ideas?
Subject: Audio input problem
From: XDA developers
Date: 26 Dec, 2002 12:06:52
The audio-input needs to have absolutely no DC bias. Coupling
the audio in through a 30 pF capacitor should do the trick.
Subject: ?
From: Carlos
Date: 26 Dec, 2002 18:56:25
The problem is not on the input side, other than the level
having to be high. A cap won't solve that since a microphone
has no DC output. I can get it to work just fine from higher
level inputs.
dated before January 19th 2003
Subject: Car kit creation issues
From: Carlos
Date: 24 Dec, 2002 22:09:25
So I'm in the process of making a full car kit for the XDA. My
goal is to provide power, serial (for GPS), and sound in/out.
I've conquered the physical part by hacking up a cradle, which
will be mounted in the car. That was more complex than it
seems. Not particularly complicated, but required work.
For the electronics, "plan A" was to simply wire the output to
the car radio and attach a standard microphone for input.
However, it appears that the microphone input requires a high
level signal. I did not get any input at all from a microphone
(yes, tested more than one). I was only able to get input by
connecting another audio device's headphone connector directly
to pin 1/Mic In, and then it wasn't as loud as I would have
expected.
Also, the sound ouput via the bottom connector is quite tinny
and faint compared to the headset output. At least, it is when
listening via headphones; maybe headphones are too low-impedance
for that output.
Hmm, ok, it does seem to be an impedance issue. When I ran that
output to a cassette adapter it sounded fine, and actually
louder than the cassette adapter plugged into the headset jack.
Ok, that's good.
So I tried "plan B"--connecting it to an existing Ericsson car
kit. However, the Ericsson's kit's electronics apparently come
from the Bizarro world. I was unable to figure out how a phone
tells the kit that there is a call and to activate itself.
There are two wires fron the Ericsson unit which do this, but
nothing seems to change with them. They keep the same voltage
and resistance whether a call is on or not. Weird.
Plan C...the only other thing I can think of is to get a
microphone to boost the input. I hesitate doing this because
I'm thinking that echo will be a problem, which is why I was
considering using the Ericsson kit anyway--excellent noise
cancellation. It appears that even a universal kit would be
unusable with this device because I don't believe they boost the
microphone at all.
Anybody got other ideas?
Subject: Audio input problem
From: XDA developers
Date: 26 Dec, 2002 12:06:52
The audio-input needs to have absolutely no DC bias. Coupling
the audio in through a 30 pF capacitor should do the trick.
Subject: ?
From: Carlos
Date: 26 Dec, 2002 18:56:25
The problem is not on the input side, other than the level
having to be high. A cap won't solve that since a microphone
has no DC output. I can get it to work just fine from higher
level inputs.