Judging by the size of the smaller phone module, I have a feeling that it only handles the communication with the GSM network and not the control of the whole unit. Kind of like the telit modules that sparkfun sell.
It also would make sense from a servicing standpoint too. If the GSM tranciever is faulty, why replace the whole control unit.
I think that the eInk driver is somewhere under the large metal backing, attached to the large board. The following pic is what I think the layout is.
On another picture from the disassembly, you can see the corner of a BGA mounted chip sticking out from a hole in the metal shield casing under the battery power connector on the GSM module.
I think your wrong, The eink driver only does 93 segments, so one is not enough. There are 2 blobs on the main PCB and they look the same, so my guess is that its 2 eink drivers.
When I was testing I managed to get a problem where only half the eink screen was being driven (supporting my theory that there are 2 eink drivers).
This would also suggest that the controller was on the module not on the board with the screen (connector seating was the problem so the spi link to one driver didnt connect).
I am definate that the 2 blobs on the main pcb are both eink drivers.
I saw the earlier post about the 2 blobs after I posted the pic, these are usually indicative of some sort of display driver, leaving my 2 suspect BGA chips as possibly some sort of ARM processor, which is the mobile phone’s CPU of choice & an external flash chip. Coupled with the fact that the phone offers voice prompts in upto 3 languages in the same phone, it needs somewhere to store the speech, and that will need a bit of flash.
The reason I think the smaller PCB on the back is just the GSM tranciever is the SIM connector, Microphone & the Test Points that give access to the RX/TX lines for RS232 access to the AT command set are all on that small PCB. Functionally it looks to be very similar to the Telit modules Sparkfun sell. If you look at the product photos of the sparkfun cellular modules, you’ll see they have a similar connector with a similar amount of pins as the motorolla module.
The way to be sure would be to interface to the TX/RX lines on the small board, putting in a SIM and connecting the battery then see if you can send AT commands. The next step would be to try and feed the larger main board 3.3v and see if it powers-up without the GSM module connected. It should give some kind of error when it can’t communicate with the module.
You will need more than 3.3v for the board, the e-ink display needs a couple of high voltages. Im not sure if they used the internal voltage regs. Just something to watch as the vreg is on the smaller board.
When I said 2 blobs, they are under the 2 sections marked in the diagram as BGA devices. These are the only 2 ICs on that main large flat PCB. Everything else is on the smaller one and they are not BGA by my understanding of the term.
When you remove the metal backing that is stuck and soldered to the large main pcb you see they are epoxy blob mounted not fully packaged ICs.
That is what leads me to beleive the phone module is complete on the second board.
Pyrofer:
When you remove the metal backing that is stuck and soldered to the large main pcb you see they are epoxy blob mounted not fully packaged ICs.
You can blob mount all sorts of chips, including ARM and Flash. You can even buy wafers of x86 chips from intel so you can blob mount them. A good indicator of what may be the microprocessor would be some sort of crystal in close proximity to the blob.
Another reason you wouldn’t want your general control microprocessor on the same board as your GSM transmitter is when the transmitter is in operation, the high-energy interference would disrupt the operation, which is why the metal shield sits between the smaller PCB and the large one.
in regard to the high voltages for the eInk display, you probably will find an inductor or two for a boost converter circuit to kick the low voltage up to what the eInk driver wants.
