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I have managed to acquire a GROM BT-3 unit but understand that it needs a RVRN2 cable to work with the Alpine HU of a 2001 Vogue. GROM do not seem to do this cable anymore! Therefore does anyone have the detail of this cable (connector pin to pin info) so I can make one up?

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Do you mean this cable?

GROM RVR Cable

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Hi Marty, I have that cable but the wiring of it doesn’t make any sense to me with regard to the pin outs on the back of the Alpine radio e.g. pins 16 & 17 on the blue mini ISO plug are connected together on pin 2 of the 20 pin connector??? This seems to suggest to me that they are the audio input grounds for the GROM! Pin 16 on the back of the Alpine HU is supposed to be +12V ignition switched and pin 17 the data ground.

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I will have a look at them in a bit as I'm actually with my laptop and RAVE... But what seems like ages ago now, I did a Grom install for someone with the BT3 unit and also that cable and it worked fine... The blue connector replaces the CD changer input on the head unit... But I will have a look through my notes and pinouts for the Alpine system and double check...

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Having a look - I believe this is right. The audio grounds (from memory) are tied to the main power ground in the head unit/Grom unit. So the pins you mentioned are to actually power the Grom BT3 unit itself. There should be other wires in the connector aswell to go to the head unit. Hopefully in Pins 13/14 (audio signal L/R +ve) and Pin 19, which is the I-bus control wire..

As long as all those pins are correct along with the power/ground wires - then you should be fine and it'll work as expected.

Cheers,
Marty

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I can’t find the pin out information for the GROM unit but, yes, all the 7 Alpine HU used pins are wired through to the GROM 20 pin connector. The GROM cable black wire (normally ground) is off the mini ISO pin 15 (brown in the vehicle wiring) which is the +12V permanent but if the switched +12V is being held, effectively, as the ground level in the GROM unit then it sort of makes sense.

I’ll connect it up and see what happens I just hope I don’t blow the head unit or the GROM unit or both!!!!

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Progress:

Connected up the GROM using the RVR cable and nothing blew up!

The good news: The iPod plays through left and right channels with amazingly good quality and full control is available from the iPod. The volume controls on the steering wheel work as does the mode switch to swap between radio, tape and GROM. CD button on the Alpine HU also calls up the GROM with CD1-01 displayed on the HU screen.

So far, so good.

The bad news (or not so good news): Pressing the CD selection buttons on the HU calls up CD2-01, CD3-01 etc. as expected but the GROM does go into ‘advanced’ mode and does not select the playlists as advertised in the instructions. The GROM remains in simple mode. Using the seek buttons either on the HU or the steering wheel does not skip to the next/previous track in manual or fast forward through the track in seek (non manual) mode as stated in the instructions. These buttons work OK for the radio and CD player so it’s not a problem with the HU or steering wheel controls.

Not a total disaster by any means as all controls are available from the iPod but a bit disappointing nonetheless.

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Further update:

Contacted GROM. They are aware of the issue. The latest BT-3 units are shipped with firmware including DAB compatibility. Apparently I need an older version of firmware which they have directed me to the download of. This will be the first time I have updated (or is that downdated?) electronics to an older version!!

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Good to hear that it all works properly with the cable and there wasn't any magic smoke soming out.

Interesting to know about the BT3 Update with DAB - I've not heard of that one before... but at least Grom are being good about it and helping you sort the firmware. I too haven't often had to downgrade firmware on things! But hopefully that will manage to get it all working as expected - I must say that the one I installed a year (or maybe 2) ago obviously didn't have that firmware, as all the track/folder control worked as you would expect it to.

Hopefully the firmware update will be easy enough to do!

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GROM told me that the latest firmware that will fully work in the P38 is BMWv21. I have downloaded it and renamed it as per instruction but now have to find a microSD card to load it on to do the update. This involves unplugging the RVR cable, removing the GROM circuit board from its housing and inserting the card into the slot on the circuit board, reconnecting the RVR cable and waiting for some flashing lights (which I haven’t located yet) to then go steady and, so they tell me, voila that’s all there is to it. Sounds simple enough . . . . . we will see. Gotta find a microSD card now and adapter - somewhere around here I have both . . . . . . but where???

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Another update:

MicroSD card found and GROM BT-3 unit reflashed with BMW v21 firmware - quick couple of flashes of a tiny lamp on the circuit board which then held steady and . . . . . . . . . all now works beautifully as advertised by GROM including the phone, USB charger and aux input.

All checked as a lash up out of the dash and final installation will have to wait until after a brief holiday next week.

I have also wired up a relay board with 8 changeover relays so the CD player can be retained (I know, I know) and switched between GROM and CD at the flick of a switch. I tried finding an 8 way change over rotary switch but failed to find one of requisite size. Besides which the relay board was only £6. This will sit with the iPod connector, USB charger and aux input jack in the central cubby so the dash will still look stock.

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I had a GROM BT-3 on my last P38 which was superb. It was a cracking piece of kit that I used for over 3 years.