Why isn’t a firmware upgrade available for the BTM43x?

There is no firmware available for download for the BTM43x as it has been very stable for the past few years. All of the BTM43x modules that were manufactured after November 1, 2010 should arrive pre-loaded with this firmware (v11.28.1.0). Version 11.28.1.0 is a comprehensive release of all previous features and bug fixes and is the default firmware loaded at production for all BT v2.0 AT modules. You can check the firmware version of your module by entering the "ati333" command in your terminal.