First if you change better set it to 115200 baud. Uploading firmware does not change baud rate because it is stored in eeprom and you did not update the eeprom.
If you have a lcd display just go to config, change baudrate, go back and store eeprom to make it effective. Then it is changed for next connection.
If not, open in eeprom editor, change there and save. But be sure to select a valid baud rate or connection gets impossible.
Last solution is uploading firmware with modified EEPROM_MODE which makes eeprom values to be copied from configuration.h.