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  1.    #1  
    I really want to build a cable for my car that has power, audio, and serial GPS and does NOT use the 2.5mm connector. I'm afraid that with repeated use, that connector will wear out or break.

    I stumbled across this:
    http://user.chollian.net/~mines/palmone.pdf

    Chapter 9 decribes the pinout of the multi-connector and indicates that there are connections for native audio and serial in addition to the USB. If this is true then building a serial cable should be pretty straightforward - easier than the methods using the Futuredial cable, as long as a 3.3v signal is adequate for the device to be attached.

    Anyone have any thoughts on this or tried to build such a cable already?

    The doc says "beta" but it is fall 2004, so should be accurate.
  2. MMT
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    #2  
    well, I just finished typing a long reply and when I tried to submit it, I was presented once again with a login screen. Upon logging in, my reply was gone. Dammit. That'll teach me to copy replies before submitting.

    The summary: yes, I built a cable like you describe, following the pinout diagrams in the PalmOne developer docs. I opened a Seidio sync/charge cable to modify it. The Seidio clips that hold the cable into the phone are weak, and it no longer makes a secure connection. Would be better to integrate the connector into a cradle.

    Problems arise when trying to make calls with the cable connected (because of the audio connections, in particular). Phone routes sound out through the audio connectors, disables microphone, and disables bluetooth headsets (at least for GSM phones). I tried over and over to leave messages for myself on my work voicemail with the cable connected, and it wasn't possible. The phone didn't pick up my voice at all.

    Would like to try Siedio adapter for the headphone jack that provides a microphone and a place to plug in a cassette adapter. Trouble is that using this for handsfree phone calls may be iffy at best because of echo problems. Sound will be coming out through car speakers and picked up by the microphone, which doesn't have noise cancellation or other DSP.

    Would also like to try Seidio cradles that have audio out, mic in, and serial GPS connectors. Heard bad things about them here:

    http://discussion.treocentral.com/sh...ighlight=2100m

    Hopefully someone makes a good cradle that works well for playing music, making calls, and connecting to GPS. We'll see...
  3. MMT
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    #3  
    one more thing: You may have trouble using TomTom with a home-made serial cable like mine. Apparently the Seidio cradles that provide a serial connection for GPS do more than just provide a straight-through serial link. See this post:

    http://discussion.treocentral.com/sh...ad.php?t=79152

    I'm kinda leaning toward getting the TomTom 5 bundle with BT GPS when it comes out next month. Apparently the GPS unit itself is very good, and after dealing with trying to use my hacked together serial cable and eTrex in the car, I'm thinking wireless would be nice. It will be good if TomTom (or PalmOne) addresses the issue of not being able to take calls easily while staying in TomTom...
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    #4  
    It sounds from that post that the Treo only supports TTL serial logic. Don't know if it's 5v ot 3.3v TTL. (I should read that PDF...)

    To support proper RS232 for devices that expect RS232, you'll need a level converter. I suggest checking out www.maxim-ic.com - They're the manufacturers of the MAX232, the most common TTL-to-RS323 IC out there. There are MAX232 variants that are easier to use (such as a built-in power supply so that you don't need to supply +-12V to the chip.) Also, almost every other major IC manufacturer makes a pin-compatible MAX232 clone. The chips can usually be found for $1-2 or less even in single quantities. (And many companies will give single-quantity free samples. Maxim is somewhat of a pain about this, National Semiconductor is a WONDERFUL company for any engineer/hobbyist to deal with. When looking for chips to work with in new designs, NatSemi is the first company I go to because they're so easy to deal with.)

    It looks like the FutureDial cable is a standard PL2303-based USB-to-serial converter minus the RS232 level converter. If you're looking for direct RS232 output, most likely the toughest part will be obtaining the connector for the 650, the second hardest (but not difficult at all) part will be building a basic MAX232-based circuit.

    Garmin GPS units are notoriously tolerant of TTL-only devices. (Or is it the other way around, I think older Garmins were TTL-only but worked fine with 90% of RS232-compliant devices without level converters.)

    Basically the difference here is the definitions of the logic levels. RS232 defines a logic 1 as +12v, and a 0 as -12v, TTL defines a 1 as the power supply voltage (5v or 3.3v), and a 0 as ground (0v). Many TTL inputs will happily work with RS232 signal levels (as long as they are capable of handling the excessive voltages, most are), RS232 inputs don't necessarily work well with TTL signal levels, but some will.
  5. MMT
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    #5  
    interesting though that a serial cable like mine (with no TTL->RS232 converter, just straight through) works with Mapopolis and Vindigo but, according to Semsons, not with TomTom. Obviously my Garmin eTrex is tolerant of TTL because it works with certain apps. I just wonder why they say it won't work with TomTom. Someone suggested in the post I originally linked to that perhaps TomTom is not activating power out on a particular pin that is required to power the TTL-RS232 converter chip, but since I don't have one of those (and I don't think the Semsons cable does either) then that can't be the issue.

    I'm still left with the conclusion that the TomTom bundle with BT GPS may be the way to go. I wanted to save some money and leverage the eTrex GPS that I already have, plus avoid the problems that others have reported with making calls while connected via BT to their GPS, but I'm not convinced that the Seidio 2100M cradle is a good solution. No BT headset compatibility with GSM 650s is a real problem by itself, and the other reported issues are not encouraging.
  6.    #6  
    Entropy, I was hoping to avoid having to do the conversion - that my eMap would work with the 3.3V swing (0v=0, 3.3v=1) but from your comment, I think you are saying that the Garmin emap might be INtolerant of the voltage. Also makes me worry that if th eMap outputs +/- 12V it might blow the serial inputs on the Treo.

    I can build the circuit and I have seen the connector on the net. I could also convert a cheap USB cable like MMT did. I have one that looks like it's doable. Power for the circuit is +5V and that's available on the mulitconnector too.

    MMT - It's possible to wire the cable so that the power to the chip does not depend on Tomtom flipping the bit.

    Gee, you would think that by now someone would have put all this together and made it work right. GPS, audio through car stereo and speakerphone. It's not rocket science. Too bad Seidio
  7. MMT
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    #7  
    For what it's worth, here's a reply I received from TomTom in response to a message I sent asking them if they knew anything about incompatibilities with TomTom on the 650 and wired GPS units:

    "Dear MMT,

    *We currently do not have a wired solution for the Treo 650.* We cannot confirm if a 3rd party wired*GPS receiver will work with the Treo 650 and our software.*If we have not tested it, it may not be best to purchase the software only package.

    Regards USAinfo"

    Not much new info there, but at least they replied...
  8. Entropy's Avatar
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    #8  
    I BELIEVE, (not totally positive) that the eMap is typically one of Garmin's most tolerant devices as far as levelshifting. I know I *don't* need to use any level converters with my eMap and true RS232 ports, I'm not sure if it's just being a tolerant 5v TTL device or if it's true RS232. I know *older* Garmins were TTL-only (on the other hand, they had built in voltage regulators and could operate from 12-30ish VDC).

    I'd have to hook up a scope or voltmeter to my eMap to verify.

    It could be that there's a software-selectable level converter in the Treo... I'd have to poke deep in the developer docs to figure that one out.

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