MSP430I2040: Is it possible to load the firmware in a .hex file through the UART for the MSP430I2040TRHBR?

Hello,

No, this is not possible natively on this device as the MSP430I20xxx series does not have a BSL. However, if you initially program in an application side BSL (See MSPBOOT on www.ti.com/tool/mspbsl ), then you can have that capability.