I finded time to look into the circuit in more details. It is too big to be ruled in one post... I would like to share were I am now before I go further. your input will help understanding the next step.
1- The LCD driver is essentially driving the LCD. I think it also output a clock signal to the transducer (switching the transducer accumulating capacitor maybe?) at a certain frequency. Thus triggering timed pulse. There is 4 com and 31 segment. A big job to hack with the arduino trick.
2- I tried to connect to the microcontroller with a serial device on the soldering pad. They are connected to RX / TX of the microcontroller, V+ and gnd. But I was not able to see or trigger any data transfer event. I used realterm and a rs232 cable "spy". Rx or tx was not blinking or doing anything.
3- The AA32416 IC (on the right corner) is were I choose to invest time for now: I figure out all the IC pin connection and this is were I need your help to go further.
Of the 16 pins, only 7 are connected and strange enough, pin 9 (IC final output pin is not connected - or I failed to find the link yet). I was expecting a lot from this pin.... (: What this IC do with only 7 pins? Can someone figure this out with my finding below?
Pin 4 and 15 are respectively Vcc (regulated 3,6 volts) and ground.
Otherwise pin 5 and 6 are individually ground through capacitor (18 pF each).
Those are The IF amplifier input pin and IF amplifer bypass pin. (see picture of the typical schematic from the IC datasheet).
Pin 8 (filter amplifier input pin) is connected to V+ through a 10k resistor.
Pin 12 (RSSI output pin) is connected to ground through a parallel arrangment of a 18 pf capacitor and a 1M resistor and it is the only pin that is connected to the microcontroller (pin 1).
Pin 14 (noise detector output pin) is connected to ground through a 18 pF capacitor.
I measure 18 pF for all capacitors. Probably it is wrong because all the part are interconnected? I probably read parallel capacitance of the circuit and this is why it is constant?
Finally, can someone explain my the basic of coil inductor (the 2 metallic square coil on the board). I google about this. They have 5 pin. 3 on one side and 2 on the other. I think the 3 pins are like potentiometer that allow to adjust the coil inductance value. The other end is fix and will act like a transformer? In any case, both coil inductor are not clearly connected to an IC. There is some transistors in between. I try to follow the signal path but my misunderstanding of the 5 pin vs the transducer input make this job much harder. I also think that the inductor on the rigth is only for reference signal since I don't see any connection with the transducer while the other one is connected to the transducer.
AA32416.pdf (419 KB)