v2.0.50

PRINT:Modify self-test cmd M3008
PRINT:Modify self-test temp and time, disable self-test when tx_error,
PRINT:Modify bed maxtemp
PRINT:1. K-value algorithm improvement; 2.It mainly solves the acceleration section E_ The width between STEP turnovers is too narrow and the high-frequency forward and reverse rotation of the motor in the deceleration section makes the>run more smoothly;
PRINT:Add nozzle down MOS tube heating detection
PRINT:Add hardware temperature MOS tube damage exception handling