PHM with On Call: Facelift P2.5 module details

[ectoplasmosis]

I have dismantled a PHM from a UK MY06 car in order to find out more about how On Call is implemented as there is so little technical information about it available online.

Casing off:


Underside of GSM modem:


The GSM module has a 2FF mini-SIM slot on the underside, with a UK Vodafone SIM inserted from the factory. This is what facilitates the On Call functionality via voice & SMS. The GSM module supports data via GPRS but this is not used by On Call.

I do not know if the module is locked to this particular SIM or if the VOC infrastructure expects all VOC requests to come via this SIM only.

I have an old Ericsson T28 that I'll be putting this ancient 2G SIM into to see what can and can't be called/SMS'ed with it.


More images of the modem, it's a Wavecom WISMO Quik Q2406A-C:




Reverse of main PCB:



Motorola GPS module and keypad PCB:





Very sturdy die-cast alloy frame:





There are no fewer than five circuit boards inside the PHM, six if you count the discreet antenna PCB soldered to the modem.

No sign of a mic/speaker in the PHM, contrary to much of the information available online. There is a discreet GPS receiver however.

All visible capacitors are solid so should last much longer than the mix of solid and electrolytic in the '00-'05 pre-facelift PHM units.

[Georgeandkira]

Thanks for the disassembly and pictures.
I do not know what a PHM is. Obviously it's the package of communications products designed into the emergency alert systems.
It takes impact data from crash sensors as well as an on/off button.

In answer to your question regarding the SIM card. I'm betting it'll work IF the circuitry pinout is the same old-to-new. I base my guess on the fact that phone company personnel could throw SIM cards at people without documentation.

What are those thick wires with the brass connectors (visible prominently in pics. #1 and 7)? I assume they're coaxial "music carriers".

Was mere interest your motivation in disassembling the unit? It had its own SIM card in it, no? Kira

[ectoplasmosis]

The PHM is the PHone Module, the numerical keypad and On Call buttons in the dash to the left of the radio in P2 cars.

The SIM card is a standard 2G Vodafone item, but obviously has some very special carrier agreement because it can be used to call/text at least the prescribed Volvo On Call centre numbers from anywhere in Europe without any end-user billing. Whether there are any limitations to this is my question.

The brown cables with brass connectors are coaxial pigtails connecting the various RF transceivers in the module to connectors on the back of the PHM that then lead to antennae affixed to the windscreen of the car. One for GPS and two for GSM. There is also a small discrete antenna PCB soldered to the GSM modem module.

I took the thing apart out of curiosity as to how the On Call system is implemented. There is very little, often conflicting, technical information about it online.

[marekbm]

quite more complex than PHM without VOC :-) . i'm quite surprised that the Wavecom modem is used because it supports only one SIM. so they have to use some multiplex system to select which SIM is used. and also it requires some extra i/o pins to drive it.

[ectoplasmosis]

Would the potential SIM multiplexing make it more or less difficult to implement On Call functionality in your Bluetooth module?

I am more than willing to post you this PHM to reverse-engineer the GSM module if it means you could retain at least some On Call functionality with your module.

[Simon Jones]

Originally Posted by marekbm

quite more complex than PHM without VOC :-) . i'm quite surprised that the Wavecom modem is used because it supports only one SIM. so they have to use some multiplex system to select which SIM is used. and also it requires some extra i/o pins to drive it.

Surely the VOC SIM is used exclusively for the emergency features, while the user-SIM is just for calls, so they are completely independent.

[marekbm]

mentioned somewhere else the VOC is not just about emergency. you can use is for many other features. and all this features have to use the VOC SIM. and also this PHM (phacelift P2.5) will not work if you put in into older model (with hu-x0x radios). so to test it you have to have also correct model year.
it will need to do reverse engineering from the scratch. so the connect serial scanner to the communication pins and find also all extra important driving pins regarding to VOC.

[stefansoderstrom]

Hi did you fine anything by tex/sms phm voc sim card?

Stefan