tmc: SET_TMC_FIELD VELOCITY

Ability to specify `VELOCITY` as a parameter for SET_TMC_FIELD. Useful for configuring at runtime the TSTEP based fields of the driver.

Signed-off-by: Alex Voinea <voinea.dragos.alexandru@gmail.com>

klippy/extras/tmc2660.py

@@ -221,6 +221,8 @@ class MCU_TMC2660_SPI:
         msg = [((val >> 16) | reg) & 0xff, (val >> 8) & 0xff, val & 0xff]
         with self.mutex:
             self.spi.spi_send(msg, minclock)
+    def get_tmc_frequency(self):
+        return None
 
 
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