Below are links to the current firmware versions for the HHa transmitter. Note that the HHa and HHa/E01 models require different firmware loads. The HHa is sold in the US and Canada; the HHa/E01 is sold in the European Union. Be sure to download the correct update file and double-check before installing!
These are zip files, after downloading extract it into a temporary folder. Use the USB Firmware Updater program to update firmware.