OS X Capable Firmware? HELP!

[bexalynn]

I am a Mac user attempting to flash a Samsung Galaxy S phone using Heimdall.
I downloaded heimdall-frontend, went through the process (Heimdall, Utilities, Detect)
and got the error message "Failed to detect compatible download-mode device."
My questions are as follows:
Do I need to download Gingerbread 2.3.5?
Do I need Firmware in order for Heimdall to detect the device?

Please help - advice & comments appreciated!

 

[anon(94115)]

did you put the phone in download mode?

 

[bexalynn]

Yes - I successfully put the phone into Download Mode.