QuoteJoeK1973 Anyway, plugged it in ... without the stepper motor connected and set vRef (initially 1.1v). Then I connected the motor and got a 'driver overtemperature' warning. How did you get the overtemperature warning without SPI? Are you sure it wasn't just noise on the wire? It seems like if you're running them in standalone mode, you shouldn't set the TMC flags in Marlin, because thereby jeffeb3 - Stepper Motors, Servo Motors, DC Motors