Keywords: avago, adbs, a320, OFN, optical finger navigation.
- Most comprehensive info on these trackpads I could find is here: https://hackaday.io/project/167075-thumbmouse/log/166999-of-trackballs-and-trackpads
- Some info is on Arduino forums (I2C variant) https://forum.arduino.cc/t/blackberry-trackpad-connector-20-small-pins-plug-or-ribbon/291406
- Some info is on Arduino forums (SPI variant) https://forum.arduino.cc/t/blackberry-joystick-navigation-key-hack/61454/13
- Module which includes I2C trackpad but without connection details https://lectronz.com/products/bb-q20-keyboard-with-trackpad-usb-i2c-pmod
The cable is 0.3mm dual-row FPC with notches (used to prevent slipping out of connector).
| Pin | Pin | Function | Wiring note |
|---|---|---|---|
| 13 | SHTDWN | Used for powersave, connect to GND | |
| 12 | GND | ||
| 11 | i2c SCL | pull-up to VDDIO | |
| 10 | MOTION_N | Interrupt out, active low | |
| 9 | i2c SDA | pull-up to VDDIO | |
| 8 | NRST | Used on initialization, pull-up to VDDIO | |
| 7 | GND | ||
| 6 | VDDA, VDDIO, VLED+ | +2.6V..3.3V | |
| 5 | DVDD | +1.8V | |
| 4 | Backlight LED + | e.g. 3.3V | |
| 3 | Backlight LED - | e.g. 200 Ohm resistor to MCU open drain output | |
| 2 | Dome switch B | ||
| 1 | Dome switch A |
I could not determine which connector is 100% compatible with this cable (notches are usually somwhere else).
Hirose FH35C-17S seems to be OK here, just two pins on each side are not connected. The FPC is too thin (0.1 mm instead of 0.2 mm), so I added a bit of kapton tape.
Also counterfeit chinese connector (white instead of brown) seems to have wrong internal dimensions, so I had to adjust a cable position in it.
Seems like noone tried to find the datasheet. All circuits with these sensors use 2.8V regulators which is totally redundant. The chip works fine with 3.3V logic and 3 kOhm pull-ups on I2C pins.
The chip has an internal +1.8 regulator, but it seems to be disabled here. Or maybe I've killed it somehow.
At one point i mixed the +1.8 and +3.3 power inputs. Surprisingly the sensor almost worked -- it had i2c address 0x33 and registers were available for reading.
The properly functioning sensor has i2c address 0x3B.
Required pins are 5 (+1.8), 6(+3.3), 7, 12, 13(GND), 8 (NRST), 9 and 10 (i2c).
I2c address: 0x3B
Product_ID (reg 0): 0x83
I highly recommend reading the datasheet Notes on Power-up section (page 15). It tells how to enable finger presence detection, configure speed switching, enable i2c burst mode.
Also datasheet describes how to change X/Y orientation in reported data.