for download you can have the latest,
but for now about v3.0 generation firmware i have no suggestion,
cause still investigate the bug. on the latest you can have v2.0 generation 518 for hw.
you asked about to calibrate hw,
try this
transmitter on.
esc off
hold red button.(while) Switch on esc.
it will red blink. release red button.
let your transmitter not moving(center), click red button once.
transmitter full forward throotle, click red button once.
transmitter full reverse throotle, click red button once.
esc switch off.
Done.