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Thread: Using an XM direct as an XMPCR

  1. #1
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    Using an XM direct as an XMPCR

    Hello everyone,
    Here is what I see as the difficulty in using the XM direct to replace the XMPCR.
    I got one over the weekend along with a smart adapter for Sony head units. I wanted to see if the XM direct could be used with software applications already written for the XMPCR. Last year, I built a stand-alone controller for my PCR with LCD display and IR remote control capability. It was getting close to completion but when the Roady 2 came out I figured why am I going through all this trouble to build it myself and I abandoned the project. So I know how to successfully talk to the XM tuner module that is in the PCR and I believe also in the XM direct.
    The first problem is that even though the XMdirect uses the same "can" tuner module as the PCR and most other XM products, the data input from the smart adapter connected between your head unit and the XM direct, translates the protocol from whatever brand head unit you have to the protocol that the XM direct understands. In other words, the data input comming in on the mini 8 pin connector on the XM direct unit goes through an RS232 to TTL level converter (max3221) then to a microprocessor (an ATMEL mega8) in the XM direct unit and then to the XM "can" tuner module . A proprietary protocol is used between the head unit, the smart adapter and the XM direct unit. The smart adapter also has a microprocessor in it (ATMEL Mega32) which translates communications from the head unit to a protocol which the XM direct understands. In contrast, in the XMPCR, the data from your pc goes through a USB to serial converter chip (FTDI) in the XMPCR and then directly to TX and RX of the the "can" tuner module. So while it is not impossible to use the XMdirect as a PCR, it will require some modifications to bypass the CPU in the XM direct and talk directly to the tuner module. There is an RS232 to TTL converter chip in the XM direct (MAX3221). Which can be used to talk with the serial port of a PC but the ATMEL CPU must be bypassed or disabled. The ATmel CPU can be tri-stated by holding reset low. This would eliminate having to cut traces to isolate it from the tuner module. This would allow you to communicate with the XMdirect using a serial port and the existing software out there but if you want USB connection then another driver chip will be required. I'm wondering if it really is worth the trouble.

  2. #2
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    I sure hope it's worth the trouble to someone as that's what I plan on trying as soon as it's figured out.

    I've debated running down to Circuit City to pick up a Direct unit, but I don't have much time to try and get it to work.

  3. #3
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    Well I am going to do whatever it takes to get it to work. Since I already have a PCR I'm not in as much of a hurry. I was hoping the XMdirect would have been an easy solution. Have you seen this thread? http://www.mp3car.com/vbulletin/showthread.php?t=33165

  4. #4
    Maximum Bitrate gork's Avatar
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    I have been looking into this project as well. I believe I hae a simple fix to make the XM Direct speak the regular XM protocol, but I will have to actually get my cable built and start testing to be sure. I'm making no guarantees, but if it works, it'd only cost about $3 in parts, though it would void your XM Direct warranty! I am working on buying a house this week, so I am a bit pressed for time, but maybe I can bounce the ideas off of those who have the time to actually solder it up and test them... Btw, dacndar you have a PM
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  5. #5
    Variable Bitrate HybridMike's Avatar
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    I have been looking into this project as well. I believe I hae a simple fix to make the XM Direct speak the regular XM protocol, but I will have to actually get my cable built and start testing to be sure. I'm making no guarantees, but if it works, it'd only cost about $3 in parts, though it would void your XM Direct warranty! I am working on buying a house this week, so I am a bit pressed for time, but maybe I can bounce the ideas off of those who have the time to actually solder it up and test them... Btw, dacndar you have a PM
    why would you void your direct warranty?
    you can do everything the pcr does through the headunit port.... besides any modifications to the xmDirect itself would put you in a legallity issue with xm....remember the reason that they discontinued the pcr is because they want to stop the mp3 recording with time trax...if you are modifiying there product you are allowing this to happen again and could put an individual at risk.....just a word of advice.....we have been working on this and I can assure you that the two devices are quite diff in protocol the main problem we have been having is getting it to sync up before the computer takes full control....and what i mean is when the unit has power applied to it (12v) the first time the headunit makes a communication with the tuner...there is some sort of syncing going on.....once this has happend we can remove the controller and operate solely on the cpu ie....power on/off channel ....ect....

    we have sent the direct to our engineer at the college here in orlando to fully analyze the syncing process.....we should know by thursday whats going on with it.

  6. #6
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    I agree that your solution is more elegant and safer as far as legalities go. I hope you succeed.
    Quote Originally Posted by HybridMike
    why would you void your direct warranty?
    you can do everything the pcr does through the headunit port.... besides any modifications to the xmDirect itself would put you in a legallity issue with xm....remember the reason that they discontinued the pcr is because they want to stop the mp3 recording with time trax...if you are modifiying there product you are allowing this to happen again and could put an individual at risk.....just a word of advice.....we have been working on this and I can assure you that the two devices are quite diff in protocol the main problem we have been having is getting it to sync up before the computer takes full control....and what i mean is when the unit has power applied to it (12v) the first time the headunit makes a communication with the tuner...there is some sort of syncing going on.....once this has happend we can remove the controller and operate solely on the cpu ie....power on/off channel ....ect....

    we have sent the direct to our engineer at the college here in orlando to fully analyze the syncing process.....we should know by thursday whats going on with it.

  7. #7
    Constant Bitrate NOS TANG's Avatar
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    Quote Originally Posted by HybridMike
    why would you void your direct warranty?
    you can do everything the pcr does through the headunit port.... besides any modifications to the xmDirect itself would put you in a legallity issue with xm....remember the reason that they discontinued the pcr is because they want to stop the mp3 recording with time trax...if you are modifiying there product you are allowing this to happen again and could put an individual at risk.....just a word of advice.....
    Mike I respect your work and advice on this subject, but I see it a bit differently. I find toslink mods and moded PCR's selling on eBay and other sites every day. The guys over at xm411 claim that xm had no problems with them making the mods, or adding them to stuff they sell as NEW.. Once you purchase a piece of equipment its yours to do with what you wish. In XM equipment cases unless you use it to steal their signal I don't think they can say jack.

    It will be nice to plug and play directly on the DIN jack, but what do you think the guys at Terk or Blitzsafe are gona have to say when you release this? They could claim infringement if they want since they are the only supplier to date for all the adapters. Blitzsafe applied for patents in January on a bunch of adapters.
    ---
    BlitzSafe President and CEO."With the new advanced applications and Recent Patent Pending innovations by BlitzSafe such as Interoperable interfaces for Satellite Radio"
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    >Pending being the key word here

    If anyone wants to void the warranty on a $50 direct or other receiver and disable or bypass the Amtel protocol conversion process so you can speak directly to the tin can in the same xm protocol as the PCR does. I say go for it.. While your in there pop in a toslink and your back to complete digital audio with TimeTrax compatibility. I'm sure the TT guys won’t mind if you do this. Plus if the word is out on a role your own fix,, less focus will be put on the plug and play fix.


  8. #8
    Low Bitrate Bryan Pape's Avatar
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    Quote Originally Posted by dacndar
    Hello everyone,
    Here is what I see as the difficulty in using the XM direct to replace the XMPCR.
    I got one over the weekend along with a smart adapter for Sony head units. I wanted to see if the XM direct could be used with software applications already written for the XMPCR. Last year, I built a stand-alone controller for my PCR with LCD display and IR remote control capability. It was getting close to completion but when the Roady 2 came out I figured why am I going through all this trouble to build it myself and I abandoned the project. So I know how to successfully talk to the XM tuner module that is in the PCR and I believe also in the XM direct.
    The first problem is that even though the XMdirect uses the same "can" tuner module as the PCR and most other XM products, the data input from the smart adapter connected between your head unit and the XM direct, translates the protocol from whatever brand head unit you have to the protocol that the XM direct understands. In other words, the data input comming in on the mini 8 pin connector on the XM direct unit goes through an RS232 to TTL level converter (max3221) then to a microprocessor (an ATMEL mega8) in the XM direct unit and then to the XM "can" tuner module . A proprietary protocol is used between the head unit, the smart adapter and the XM direct unit. The smart adapter also has a microprocessor in it (ATMEL Mega32) which translates communications from the head unit to a protocol which the XM direct understands. In contrast, in the XMPCR, the data from your pc goes through a USB to serial converter chip (FTDI) in the XMPCR and then directly to TX and RX of the the "can" tuner module. So while it is not impossible to use the XMdirect as a PCR, it will require some modifications to bypass the CPU in the XM direct and talk directly to the tuner module. There is an RS232 to TTL converter chip in the XM direct (MAX3221). Which can be used to talk with the serial port of a PC but the ATMEL CPU must be bypassed or disabled. The ATmel CPU can be tri-stated by holding reset low. This would eliminate having to cut traces to isolate it from the tuner module. This would allow you to communicate with the XMdirect using a serial port and the existing software out there but if you want USB connection then another driver chip will be required. I'm wondering if it really is worth the trouble.

    You mentioned that this is an Atmel. Is it an AVR? If so, what kind of package. (I'll have to look at the XMPCR to see what it's using) Perhaps it's possible to reprogram with JTAG (from a parallel port). Additionally, it seems to me that figuring out the "proprietary protocol" used between the headunit and the XM Direct should actually be rather straight forward - i.e. If you press a button, what does it spit out. The nice thing is that the 8-pin din is already RS-232 instead of TTL. I would think that creating an interface in software should actually be rather easym.

  9. #9
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    Yes, it is an AVR Mega8 processor in the MLF package. The main problem right now is the Sony head unit I have was suppossed to be XMdirect compatible according to the list I had but I've since found out its not. So I have no way at the moment to manipulate a head unit to see what comes out. I have a PCR and I can tell you that there is no CPU between the input of the "can" and the PC. Only an FTDI USB to serial chip. The Mega8 in the XMdirect and the Mega32 in the "smart adapter" I have for the Sony head units are talking between each other to convert the head units protocol to what the XM direct is designed to speak. Then the the Mega8 inside the XMdirect talks to the "can".
    Hope this clarifies.
    Quote Originally Posted by Bryan Pape
    You mentioned that this is an Atmel. Is it an AVR? If so, what kind of package. (I'll have to look at the XMPCR to see what it's using) Perhaps it's possible to reprogram with JTAG (from a parallel port). Additionally, it seems to me that figuring out the "proprietary protocol" used between the headunit and the XM Direct should actually be rather straight forward - i.e. If you press a button, what does it spit out. The nice thing is that the 8-pin din is already RS-232 instead of TTL. I would think that creating an interface in software should actually be rather easym.

  10. #10
    Constant Bitrate NOS TANG's Avatar
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    Sounds correct to me dacndar.
    My question, and everyone else I have spoken to is, what the hell does that direct receiver talk on the DIN plug? This is the true $100 question. I have not seen a single HU out there that will work with it plug to plug. The only thing that I know it works with is the commander digital control interface. You said you have the smart adapter for your HU, have you cracked it open to play with yet? I would like to see the inside of one if you have any pictures. No wonder they sell the direct for $50 it's useless alone, you have to give the manufacture another $50 to just make it work.

    My first idea was to flash the Atmel on the xmdirect board with a new protocol that we can work with as Bryan suggested. This would be a software fix vs hardware fix. Doing something down this line might be and easier solution unless someone can reverse engineer the existing “one off” protocol.

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