Serial Mouse Converter
======================
This makes old serial mouse into modern USB one.

Tested by:
- Microsoft green-eyed mouse
- DELL mouse can work with DTR only.


Pinout
------

    DE-9    DB-25   DTE DCE     Description
    ----------------------------------------------------------------
    2       3       RXD TXD     data from mouse
    3       2       TXD RXD     used by mouse as power source?
    4       20      DTR DSR     used by mouse as power source
    5       7       GND GND
    7       4       RTS CTS     used by mouse as power source
    *DTE=Converter, DCE=Mouse



## RS-232 Driver
Microsoft mouse seems to need higher voltage for power source.
SP3232E outputs only +-6V at charge pump output and didn't work.
ADM232A works for both Microsoft and DELL.

Microsoft green-eyed mouse requires both while DELL mouse can work with DTR only.


## Wiring
Mouse RXD, TXD, DTR and RTS should be wired to RS-232 driver.
Wire up RS-232 driver charge pump output V+ to DTR and RTS for power source purpose.

Connect Mouse TXD to AVR PD2(RXD) *through* RS-232 driver for mouse data.



UART Setting
------------
defined in config.h.

### Microsoft serial mouse
1200 baud, 7-bit data, no parity, 1-bit stop, lsb-first

### MouseSystems
1200 baud, 8-bit data, no parity, 1-bit stop, lsb-first(Not tested)


Resources
---------
Get power out of PC RS-232 port:
https://www.epanorama.net/circuits/rspower.html

Microsoft serial mouse:
https://web.archive.org/web/20130307230349/www.kryslix.com/nsfaq/Q.12.html

Serial Mice Protocols:
https://roborooter.com/post/serial-mice/