Is There a psqlODBC + iODBC HOWTO?

I'm new to psqlODBC but have used iODBC in the past.  I haven't found
any documentation on the DSN format in $ODBCINI.

I've grasped at straws to no avail.  Best I get from iodbctest is:
"SQLDriverConnectW = connction string lacks some options (202)
SQLSTATE=08001"

Is there a HOWTO or can someone point me in the right direction?

Many thanks.

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Regards,

Scott Dudley