tmc5160: allow changing the globalscaler at runtime

Previously, the globalscaler was calculated during the config parsing and set to a fixed value. If the current was changed for any reason after the initialization, only IRUN and IHOLD would be changed. This however caused issues:
- If the new current was lower, then the resolution of the possible current values would be low since there are only 32 IRUN/IHOLD steps.
- If the new current was higher, it wouldn't actually work since IRUN and IHOLD are capped at 31, so it wouldn't be possible to increase the current without increasing globalscaler.

With this commit, the globalscaler is recalculated whenever necessary in order to ensure the correct range of IRUN/IHOLD is used.

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

docs/Config_Changes.md

@@ -8,6 +8,14 @@ All dates in this document are approximate.
 
 ## Changes
 
+20230304: The `SET_TMC_CURRENT` command now properly adjusts the globalscaler
+register for drivers that have it. This removes a limitation where on tmc5160,
+the currents could not be raised higher with `SET_TMC_CURRENT` than the
+`run_current` value set in the config file.
+However, this has a side effect: After running `SET_TMC_CURRENT`, the stepper
+must be held at standstill for >130ms in case StealthChop2 is used so that the
+AT#1 calibration gets executed by the driver.
+
 20230202: The format of the `printer.screws_tilt_adjust` status
 information has changed. The information is now stored as a dictionary of
 screws with the resulting measurements. See the

docs/G-Codes.md

@@ -1226,7 +1226,10 @@ turned off then back on.
 #### SET_TMC_CURRENT
 `SET_TMC_CURRENT STEPPER=<name> CURRENT=<amps> HOLDCURRENT=<amps>`:
 This will adjust the run and hold currents of the TMC driver.
-(HOLDCURRENT is not applicable to tmc2660 drivers.)
+`HOLDCURRENT` is not applicable to tmc2660 drivers.
+When used on a driver which has the `globalscaler` field (tmc5160 and tmc2240),
+if StealthChop2 is used, the stepper must be held at standstill for >130ms so
+that the driver executes the AT#1 calibration.
 
 #### SET_TMC_FIELD
 `SET_TMC_FIELD STEPPER=<name> FIELD=<field> VALUE=<value>`: This will

klippy/extras/tmc5160.py

@@ -264,19 +264,18 @@ class TMC5160CurrentHelper:
                                        above=0., maxval=MAX_CURRENT)
         self.req_hold_current = hold_current
         self.sense_resistor = config.getfloat('sense_resistor', 0.075, above=0.)
-        self._set_globalscaler(run_current)
-        irun, ihold = self._calc_current(run_current, hold_current)
+        gscaler, irun, ihold = self._calc_current(run_current, hold_current)
+        self.fields.set_field("globalscaler", gscaler)
         self.fields.set_field("ihold", ihold)
         self.fields.set_field("irun", irun)
-    def _set_globalscaler(self, current):
+    def _calc_globalscaler(self, current):
         globalscaler = int((current * 256. * math.sqrt(2.)
                             * self.sense_resistor / VREF) + .5)
         globalscaler = max(32, globalscaler)
         if globalscaler >= 256:
             globalscaler = 0
-        self.fields.set_field("globalscaler", globalscaler)
-    def _calc_current_bits(self, current):
-        globalscaler = self.fields.get_field("globalscaler")
+        return globalscaler
+    def _calc_current_bits(self, current, globalscaler):
         if not globalscaler:
             globalscaler = 256
         cs = int((current * 256. * 32. * math.sqrt(2.) * self.sense_resistor)
@@ -284,9 +283,10 @@ class TMC5160CurrentHelper:
                  - 1. + .5)
         return max(0, min(31, cs))
     def _calc_current(self, run_current, hold_current):
-        irun = self._calc_current_bits(run_current)
-        ihold = self._calc_current_bits(min(hold_current, run_current))
-        return irun, ihold
+        gscaler = self._calc_globalscaler(run_current)
+        irun = self._calc_current_bits(run_current, gscaler)
+        ihold = self._calc_current_bits(min(hold_current, run_current), gscaler)
+        return gscaler, irun, ihold
     def _calc_current_from_field(self, field_name):
         globalscaler = self.fields.get_field("globalscaler")
         if not globalscaler:
@@ -300,7 +300,9 @@ class TMC5160CurrentHelper:
         return run_current, hold_current, self.req_hold_current, MAX_CURRENT
     def set_current(self, run_current, hold_current, print_time):
         self.req_hold_current = hold_current
-        irun, ihold = self._calc_current(run_current, hold_current)
+        gscaler, irun, ihold = self._calc_current(run_current, hold_current)
+        val = self.fields.set_field("globalscaler", gscaler)
+        self.mcu_tmc.set_register("GLOBALSCALER", val, print_time)
         self.fields.set_field("ihold", ihold)
         val = self.fields.set_field("irun", irun)
         self.mcu_tmc.set_register("IHOLD_IRUN", val, print_time)