As I said earlier, you should try turning on/blinking an LED in loader/<camera>/entry.S or main.c. There is a commented example of this in the D10 entry.S.
If you haven't found an LED address, you should find one. You can do this by analyzing the firmware or brute force search, but just trying addresses used by other recent firmware is probably good enough. If you aren't sure your diskboot is loading, you can try poking the LED addresses in a canon basic script. See
http://chdk.wikia.com/wiki/Canon_BasicYou can probably leave out the "turn off SD card" stuff. It may not be needed and in any case if you just copied the MMIO address will likely be wrong anyway. Poking random MMIOs could cause problems, so it's better to leave it out unless you verify that you need it and find the correct address.
A3300 appears to use the dancingbits 6 encoding, like other dryos R47 cams (based on the function at FFA0BE44, found by the string "not executable")
edit: address is from 100d, other firmwares may vary slightly.
If you build generate stubs_entry.S (this is optional in the build, but required for a new port) the sig finder will put a lot of useful information in comments there. In chdkshell, this is turned on in compile options under OPT_GEN_STUBS. You also need the firmware dump either in the platform/sub directory, or located by PRIMARY_ROOT.
This will find many of the addresses and constants for you. The resulting addresses should be verified by analyzing the disassembled firmware dump. Anything that isn't found by the sig finder needs to be found manually. If you cannot do this, you cannot make a port.