Loading Firmware Changes the RS-232 Speed

Firmware is always sent at 38,400 bits per second (bit/s).

The KX2 Utility determines the KX2's initial RS-232 speed by analyzing responses to short "no operation" commands (;) sent at various speeds. The KX2 Utility then changes the KX2 to 38,400 bit/s to send firmware. After firmware is sent, the KX2 Utility attempts to change the KX2's RS-232 speed back to the original value.

If the operation is interrupted or communications cannot be established with the KX2's MCU after sending firmware, the KX2 Utility cannot restore the RS-232 speed to its original value. After restart, the you may find the RS-232 speed set to 38,400 bit/s.

The KX2 commands used to change RS-232 speed require interaction with operational MCU firmware. A KX2 in its "boot loader" state, indicated by a KX2 display showing "MCU LD" and a red Tx light, communicates only at 38,400 bit/s. Once MCU firmware is loaded, the speed last used by the most recently-loaded MCU firmware is discovered (by polling at all the KX2's supported speeds) and that's where it is left after firmware load is complete.

RS-232 speed changes are displayed in the Activity Log.

If the KX2's RS-232 speed needs to be changed, use the KX2 CONFIG:RS-232 menu selection.

You may also use the Command Tester to enter a KX2 "br" command to change the KX2's RS-232 speed:

The Elecraft K3 and KX2 Programmer's Reference provides KX2 command information.

After you change the RS-232 speed with the KX2 CONFIG:RS-232 menu or the Command Tester, use the Test Communications button to allow the KX2 Utility to discover the KX2's current RS-232 speed.