ADNS-7550 laser sensor chip for quadrature output mouse
This project is based on a Dell mouse which is run by an unknown micro-controller, and SPI ADNS-7550 sensor chip. It made a very easy for me to modify it and drop in msp430g2553 micro-chip in the same spot, after a handful of easy modifications: trace-cuts, and wire jumpers. A full schematic is missing but the pin assignment should tell whole story:
______________
Vcc | 1 20 | GND DB9 8
top button P1_0 | | P2_6 QRA
MOTION/IRQ P1_1 | | P2_7 QRB
CS P1_2 | | TEST
DB9 5 MMB P1_3 | 5 | RESET
mmb-in P1_4 | | P1_7 MOSI
CLK P1_5 | | P1_6 MISO
XQ DB9 4 QXA P2_0 | | P2_5 5th button
X DB9 2 QXB P2_1 | | P2_4 4th button
Y DB9 1 QYB P2_2 |_10______11_| P2_3 QYA DB9 3 YQ
mouse pinout DB9:
QYB QXB QYA QXA
Y X YQ XQ MMB DB9 color UTP MCU
U D L R PotY 1 red w/grn 10
_______________________ 2 blk w/brw 9
\ 1 2 3 4 5 / 3 gry w/blu 11
\ / 4 org org 8
\__6___7___8___9_ / 5 brw brw 5
LMB + gnd RMB 6 grn grn LMB
PotX 7 wht blu +5vcc
8 blu shield GND
9 ylw w/org RMB
Among not included components in the above schematics is 3.3V regulator, necessary to run MSP430 at it maximum clock 16MHz. It is supplied from 5V at pin 7 of DB9 port. Wire colors listed are for own reference (happened to be the one in the game controller replacement cable (DB9) offered on one of the far-east on-line retail shop)
Before desoldering controller chip from the original mouse, dump the calibration values that are send during boot-up. Write down what values are written to register 0x1a LASER_CFG0/1 (0x1f) and 0x1c LSRPWR_CFG0/1 (0x1d). See datasheet page 7 for details.
- at constant intervals (
VerticalBlankISR), host is polling with a low level at MMB line - controller reacts at the falling edge of MMB linkage (see marker 1 - blue line MMB)
- quadrature lines are negated with command for a brief movement (20us ... 40us) (see marker 2 - lines QXB and QYB)
- after restoring original state of quadrature lines, state of MMB is checked to verify reception
- if MMB line is still low - treat transaction as successfully (see marker 3)
Corresponding host driver software can be obtained from AmigaMouse repository.
Case can be easily opened, even without removing front latches. Pins 1 (Vcc), 20 (GND), 16 (RESET) and 17 (TST) can be reached with small programming terminals (clips).
