Processors And Operating Systems; The Chdk: What It Is And How It Works; History - Canon Camera Hackers Manual

2.2

Processors and operating systems

Since 2002, Canon has used the DIGIC processor in all of its digital cameras,
including the EOS DSLRs. The original DIGIC processor was followed in 2004
by the DIGIC II processor, which combines all functions on a single chip (the
original processor needed three chips). DIGIC II was followed in 2007 by
DIGIC III, which brought new features such as face recognition and iSAPS
scene-recognition technology. DIGIC IV was introduced in 2008 and fea-
tures faster and better image processing and live face detection.
DIGIC II and some DIGIC III processors are equipped with the VxWorks
operating system from Wind River Systems. In 2007, Canon introduced its
own operating system called DryOS that has been used since then on most
DIGIC III and DIGIC IV platforms. DryOS can run on more than 10 different
processor types.
Compact cameras using the DryOS are: A470, A480, A580, A590 IS,
A650 IS, A720 IS, A1000 IS, A1100 IS, A2000 IS, A2100 IS, D10, E1, G9, G10,
G11, SD1100 IS (IXUS80 IS), SD770 IS (IXUS85 IS), SD780 IS (IXUS100IS),
SD790 IS (IXUS90 IS), SD1200 IS (IXUS95 IS), SD960 IS (IXUS110 IS), SD940 IS
(IXUS120 IS), SD980 IS (IXUS200 IS), SD870 IS (IXUS860 IS), SD880 IS
(IXUS870 IS), SD950 IS (IXUS960 IS), S5 IS, S90, SX1 IS, SX10 IS, SX20 IS,
SX100 IS, SX110 IS, and SX200 IS.
The distinction between the operating systems is important because
some CHDK scripting functions depend on the operating systems. Scripts
utilizing these functions usually run only on the platform they were devel-
oped for, or they must implement special provisions for cross-platform op-
eration. Developing platform-dependent scripts is fine for home use. When
publishing scripts for a larger audience, however, portable scripts are defi-
nitely the preferred solution. Newer versions of the CHDK allow access to
most camera functions in a platform-independent way, so that with some
care, portable scripts can be developed without much difficulty.
2.3

The CHDK: What it is and how it works

2.3.1 History

The development of the CHDK began in 2006 with the Russian program-
mer VitalyB. Studying the disassembly of a firmware upgrade for a Canon
IXUS camera, he was able to analyze the upgrade process and write a pro-
gram that would boot from the card and take control of the camera. With
the help of this program, he was able to read out (dump) the original Canon
operating system from the camera to a PC. Data transfer used the blue
camera LED and a phototransistor, a method still employed today with
some cameras.
2.2 Processors and operating systems
Figure 2-1
The CHDK logo shows up during the
boot process of the CHDK. The logo
display can be switched off via the
CHDK menu function
Miscellaneous Stuff
Screen on Load.
5
ALT > MENU >
> Show Splash