klipper/klippy/extras/tmc.py

614 lines
29 KiB
Python

# Common helper code for TMC stepper drivers
#
# Copyright (C) 2018-2020 Kevin O'Connor <kevin@koconnor.net>
#
# This file may be distributed under the terms of the GNU GPLv3 license.
import logging, collections
import stepper
######################################################################
# Field helpers
######################################################################
# Return the position of the first bit set in a mask
def ffs(mask):
return (mask & -mask).bit_length() - 1
class FieldHelper:
def __init__(self, all_fields, signed_fields=[], field_formatters={},
registers=None):
self.all_fields = all_fields
self.signed_fields = {sf: 1 for sf in signed_fields}
self.field_formatters = field_formatters
self.registers = registers
if self.registers is None:
self.registers = collections.OrderedDict()
self.field_to_register = { f: r for r, fields in self.all_fields.items()
for f in fields }
def lookup_register(self, field_name, default=None):
return self.field_to_register.get(field_name, default)
def get_field(self, field_name, reg_value=None, reg_name=None):
# Returns value of the register field
if reg_name is None:
reg_name = self.field_to_register[field_name]
if reg_value is None:
reg_value = self.registers.get(reg_name, 0)
mask = self.all_fields[reg_name][field_name]
field_value = (reg_value & mask) >> ffs(mask)
if field_name in self.signed_fields and ((reg_value & mask)<<1) > mask:
field_value -= (1 << field_value.bit_length())
return field_value
def set_field(self, field_name, field_value, reg_value=None, reg_name=None):
# Returns register value with field bits filled with supplied value
if reg_name is None:
reg_name = self.field_to_register[field_name]
if reg_value is None:
reg_value = self.registers.get(reg_name, 0)
mask = self.all_fields[reg_name][field_name]
new_value = (reg_value & ~mask) | ((field_value << ffs(mask)) & mask)
self.registers[reg_name] = new_value
return new_value
def set_config_field(self, config, field_name, default):
# Allow a field to be set from the config file
config_name = "driver_" + field_name.upper()
reg_name = self.field_to_register[field_name]
mask = self.all_fields[reg_name][field_name]
maxval = mask >> ffs(mask)
if maxval == 1:
val = config.getboolean(config_name, default)
elif field_name in self.signed_fields:
val = config.getint(config_name, default,
minval=-(maxval//2 + 1), maxval=maxval//2)
else:
val = config.getint(config_name, default, minval=0, maxval=maxval)
return self.set_field(field_name, val)
def pretty_format(self, reg_name, reg_value):
# Provide a string description of a register
reg_fields = self.all_fields.get(reg_name, {})
reg_fields = sorted([(mask, name) for name, mask in reg_fields.items()])
fields = []
for mask, field_name in reg_fields:
field_value = self.get_field(field_name, reg_value, reg_name)
sval = self.field_formatters.get(field_name, str)(field_value)
if sval and sval != "0":
fields.append(" %s=%s" % (field_name, sval))
return "%-11s %08x%s" % (reg_name + ":", reg_value, "".join(fields))
def get_reg_fields(self, reg_name, reg_value):
# Provide fields found in a register
reg_fields = self.all_fields.get(reg_name, {})
return {field_name: self.get_field(field_name, reg_value, reg_name)
for field_name, mask in reg_fields.items()}
######################################################################
# Periodic error checking
######################################################################
class TMCErrorCheck:
def __init__(self, config, mcu_tmc):
self.printer = config.get_printer()
name_parts = config.get_name().split()
self.stepper_name = ' '.join(name_parts[1:])
self.mcu_tmc = mcu_tmc
self.fields = mcu_tmc.get_fields()
self.check_timer = None
self.last_drv_status = self.last_drv_fields = None
# Setup for GSTAT query
reg_name = self.fields.lookup_register("drv_err")
if reg_name is not None:
self.gstat_reg_info = [0, reg_name, 0xffffffff, 0xffffffff, 0]
else:
self.gstat_reg_info = None
self.clear_gstat = True
# Setup for DRV_STATUS query
self.irun_field = "irun"
reg_name = "DRV_STATUS"
mask = err_mask = cs_actual_mask = 0
if name_parts[0] == 'tmc2130':
# TMC2130 driver quirks
self.clear_gstat = False
cs_actual_mask = self.fields.all_fields[reg_name]["cs_actual"]
elif name_parts[0] == 'tmc2660':
# TMC2660 driver quirks
self.irun_field = "cs"
reg_name = "READRSP@RDSEL2"
cs_actual_mask = self.fields.all_fields[reg_name]["se"]
err_fields = ["ot", "s2ga", "s2gb", "s2vsa", "s2vsb"]
warn_fields = ["otpw", "t120", "t143", "t150", "t157"]
for f in err_fields + warn_fields:
if f in self.fields.all_fields[reg_name]:
mask |= self.fields.all_fields[reg_name][f]
if f in err_fields:
err_mask |= self.fields.all_fields[reg_name][f]
self.drv_status_reg_info = [0, reg_name, mask, err_mask, cs_actual_mask]
# Setup for temperature query
self.adc_temp = None
self.adc_temp_reg = self.fields.lookup_register("adc_temp")
def _query_register(self, reg_info, try_clear=False):
last_value, reg_name, mask, err_mask, cs_actual_mask = reg_info
cleared_flags = 0
count = 0
while 1:
try:
val = self.mcu_tmc.get_register(reg_name)
except self.printer.command_error as e:
count += 1
if count < 3 and str(e).startswith("Unable to read tmc uart"):
# Allow more retries on a TMC UART read error
reactor = self.printer.get_reactor()
reactor.pause(reactor.monotonic() + 0.050)
continue
raise
if val & mask != last_value & mask:
fmt = self.fields.pretty_format(reg_name, val)
logging.info("TMC '%s' reports %s", self.stepper_name, fmt)
reg_info[0] = last_value = val
if not val & err_mask:
if not cs_actual_mask or val & cs_actual_mask:
break
irun = self.fields.get_field(self.irun_field)
if self.check_timer is None or irun < 4:
break
if (self.irun_field == "irun"
and not self.fields.get_field("ihold")):
break
# CS_ACTUAL field of zero - indicates a driver reset
count += 1
if count >= 3:
fmt = self.fields.pretty_format(reg_name, val)
raise self.printer.command_error("TMC '%s' reports error: %s"
% (self.stepper_name, fmt))
if try_clear and val & err_mask:
try_clear = False
cleared_flags |= val & err_mask
self.mcu_tmc.set_register(reg_name, val & err_mask)
return cleared_flags
def _query_temperature(self):
try:
self.adc_temp = self.mcu_tmc.get_register(self.adc_temp_reg)
except self.printer.command_error as e:
# Ignore comms error for temperature
self.adc_temp = None
return
def _do_periodic_check(self, eventtime):
try:
self._query_register(self.drv_status_reg_info)
if self.gstat_reg_info is not None:
self._query_register(self.gstat_reg_info)
if self.adc_temp_reg is not None:
self._query_temperature()
except self.printer.command_error as e:
self.printer.invoke_shutdown(str(e))
return self.printer.get_reactor().NEVER
return eventtime + 1.
def stop_checks(self):
if self.check_timer is None:
return
self.printer.get_reactor().unregister_timer(self.check_timer)
self.check_timer = None
def start_checks(self):
if self.check_timer is not None:
self.stop_checks()
cleared_flags = 0
self._query_register(self.drv_status_reg_info)
if self.gstat_reg_info is not None:
cleared_flags = self._query_register(self.gstat_reg_info,
try_clear=self.clear_gstat)
reactor = self.printer.get_reactor()
curtime = reactor.monotonic()
self.check_timer = reactor.register_timer(self._do_periodic_check,
curtime + 1.)
if cleared_flags:
reset_mask = self.fields.all_fields["GSTAT"]["reset"]
if cleared_flags & reset_mask:
return True
return False
def get_status(self, eventtime=None):
if self.check_timer is None:
return {'drv_status': None, 'temperature': None}
temp = None
if self.adc_temp is not None:
temp = round((self.adc_temp - 2038) / 7.7, 2)
last_value, reg_name = self.drv_status_reg_info[:2]
if last_value != self.last_drv_status:
self.last_drv_status = last_value
fields = self.fields.get_reg_fields(reg_name, last_value)
self.last_drv_fields = {n: v for n, v in fields.items() if v}
return {'drv_status': self.last_drv_fields, 'temperature': temp}
######################################################################
# G-Code command helpers
######################################################################
class TMCCommandHelper:
def __init__(self, config, mcu_tmc, current_helper):
self.printer = config.get_printer()
self.stepper_name = ' '.join(config.get_name().split()[1:])
self.name = config.get_name().split()[-1]
self.mcu_tmc = mcu_tmc
self.current_helper = current_helper
self.echeck_helper = TMCErrorCheck(config, mcu_tmc)
self.fields = mcu_tmc.get_fields()
self.read_registers = self.read_translate = None
self.toff = None
self.mcu_phase_offset = None
self.stepper = None
self.stepper_enable = self.printer.load_object(config, "stepper_enable")
self.printer.register_event_handler("stepper:sync_mcu_position",
self._handle_sync_mcu_pos)
self.printer.register_event_handler("stepper:set_sdir_inverted",
self._handle_sync_mcu_pos)
self.printer.register_event_handler("klippy:mcu_identify",
self._handle_mcu_identify)
self.printer.register_event_handler("klippy:connect",
self._handle_connect)
# Set microstep config options
TMCMicrostepHelper(config, mcu_tmc)
# Register commands
gcode = self.printer.lookup_object("gcode")
gcode.register_mux_command("SET_TMC_FIELD", "STEPPER", self.name,
self.cmd_SET_TMC_FIELD,
desc=self.cmd_SET_TMC_FIELD_help)
gcode.register_mux_command("INIT_TMC", "STEPPER", self.name,
self.cmd_INIT_TMC,
desc=self.cmd_INIT_TMC_help)
gcode.register_mux_command("SET_TMC_CURRENT", "STEPPER", self.name,
self.cmd_SET_TMC_CURRENT,
desc=self.cmd_SET_TMC_CURRENT_help)
def _init_registers(self, print_time=None):
# Send registers
for reg_name, val in self.fields.registers.items():
self.mcu_tmc.set_register(reg_name, val, print_time)
cmd_INIT_TMC_help = "Initialize TMC stepper driver registers"
def cmd_INIT_TMC(self, gcmd):
logging.info("INIT_TMC %s", self.name)
print_time = self.printer.lookup_object('toolhead').get_last_move_time()
self._init_registers(print_time)
cmd_SET_TMC_FIELD_help = "Set a register field of a TMC driver"
def cmd_SET_TMC_FIELD(self, gcmd):
field_name = gcmd.get('FIELD').lower()
reg_name = self.fields.lookup_register(field_name, None)
if reg_name is None:
raise gcmd.error("Unknown field name '%s'" % (field_name,))
value = gcmd.get_int('VALUE', None)
velocity = gcmd.get_float('VELOCITY', None, minval=0.)
tmc_frequency = self.mcu_tmc.get_tmc_frequency()
if tmc_frequency is None and velocity is not None:
raise gcmd.error("VELOCITY parameter not supported by this driver")
if (value is None) == (velocity is None):
raise gcmd.error("Specify either VALUE or VELOCITY")
if velocity is not None:
step_dist = self.stepper.get_step_dist()
mres = self.fields.get_field("mres")
value = TMCtstepHelper(step_dist, mres, tmc_frequency,
velocity)
reg_val = self.fields.set_field(field_name, value)
print_time = self.printer.lookup_object('toolhead').get_last_move_time()
self.mcu_tmc.set_register(reg_name, reg_val, print_time)
cmd_SET_TMC_CURRENT_help = "Set the current of a TMC driver"
def cmd_SET_TMC_CURRENT(self, gcmd):
ch = self.current_helper
prev_cur, prev_hold_cur, req_hold_cur, max_cur = ch.get_current()
run_current = gcmd.get_float('CURRENT', None, minval=0., maxval=max_cur)
hold_current = gcmd.get_float('HOLDCURRENT', None,
above=0., maxval=max_cur)
if run_current is not None or hold_current is not None:
if run_current is None:
run_current = prev_cur
if hold_current is None:
hold_current = req_hold_cur
toolhead = self.printer.lookup_object('toolhead')
print_time = toolhead.get_last_move_time()
ch.set_current(run_current, hold_current, print_time)
prev_cur, prev_hold_cur, req_hold_cur, max_cur = ch.get_current()
# Report values
if prev_hold_cur is None:
gcmd.respond_info("Run Current: %0.2fA" % (prev_cur,))
else:
gcmd.respond_info("Run Current: %0.2fA Hold Current: %0.2fA"
% (prev_cur, prev_hold_cur))
# Stepper phase tracking
def _get_phases(self):
return (256 >> self.fields.get_field("mres")) * 4
def get_phase_offset(self):
return self.mcu_phase_offset, self._get_phases()
def _query_phase(self):
field_name = "mscnt"
if self.fields.lookup_register(field_name, None) is None:
# TMC2660 uses MSTEP
field_name = "mstep"
reg = self.mcu_tmc.get_register(self.fields.lookup_register(field_name))
return self.fields.get_field(field_name, reg)
def _handle_sync_mcu_pos(self, stepper):
if stepper.get_name() != self.stepper_name:
return
try:
driver_phase = self._query_phase()
except self.printer.command_error as e:
logging.info("Unable to obtain tmc %s phase", self.stepper_name)
self.mcu_phase_offset = None
enable_line = self.stepper_enable.lookup_enable(self.stepper_name)
if enable_line.is_motor_enabled():
raise
return
if not stepper.get_dir_inverted()[0]:
driver_phase = 1023 - driver_phase
phases = self._get_phases()
phase = int(float(driver_phase) / 1024 * phases + .5) % phases
moff = (phase - stepper.get_mcu_position()) % phases
if self.mcu_phase_offset is not None and self.mcu_phase_offset != moff:
logging.warning("Stepper %s phase change (was %d now %d)",
self.stepper_name, self.mcu_phase_offset, moff)
self.mcu_phase_offset = moff
# Stepper enable/disable tracking
def _do_enable(self, print_time):
try:
if self.toff is not None:
# Shared enable via comms handling
self.fields.set_field("toff", self.toff)
self._init_registers()
did_reset = self.echeck_helper.start_checks()
if did_reset:
self.mcu_phase_offset = None
# Calculate phase offset
if self.mcu_phase_offset is not None:
return
gcode = self.printer.lookup_object("gcode")
with gcode.get_mutex():
if self.mcu_phase_offset is not None:
return
logging.info("Pausing toolhead to calculate %s phase offset",
self.stepper_name)
self.printer.lookup_object('toolhead').wait_moves()
self._handle_sync_mcu_pos(self.stepper)
except self.printer.command_error as e:
self.printer.invoke_shutdown(str(e))
def _do_disable(self, print_time):
try:
if self.toff is not None:
val = self.fields.set_field("toff", 0)
reg_name = self.fields.lookup_register("toff")
self.mcu_tmc.set_register(reg_name, val, print_time)
self.echeck_helper.stop_checks()
except self.printer.command_error as e:
self.printer.invoke_shutdown(str(e))
def _handle_mcu_identify(self):
# Lookup stepper object
force_move = self.printer.lookup_object("force_move")
self.stepper = force_move.lookup_stepper(self.stepper_name)
# Note pulse duration and step_both_edge optimizations available
self.stepper.setup_default_pulse_duration(.000000100, True)
def _handle_stepper_enable(self, print_time, is_enable):
if is_enable:
cb = (lambda ev: self._do_enable(print_time))
else:
cb = (lambda ev: self._do_disable(print_time))
self.printer.get_reactor().register_callback(cb)
def _handle_connect(self):
# Check if using step on both edges optimization
pulse_duration, step_both_edge = self.stepper.get_pulse_duration()
if step_both_edge:
self.fields.set_field("dedge", 1)
# Check for soft stepper enable/disable
enable_line = self.stepper_enable.lookup_enable(self.stepper_name)
enable_line.register_state_callback(self._handle_stepper_enable)
if not enable_line.has_dedicated_enable():
self.toff = self.fields.get_field("toff")
self.fields.set_field("toff", 0)
logging.info("Enabling TMC virtual enable for '%s'",
self.stepper_name)
# Send init
try:
self._init_registers()
except self.printer.command_error as e:
logging.info("TMC %s failed to init: %s", self.name, str(e))
# get_status information export
def get_status(self, eventtime=None):
cpos = None
if self.stepper is not None and self.mcu_phase_offset is not None:
cpos = self.stepper.mcu_to_commanded_position(self.mcu_phase_offset)
current = self.current_helper.get_current()
res = {'mcu_phase_offset': self.mcu_phase_offset,
'phase_offset_position': cpos,
'run_current': current[0],
'hold_current': current[1]}
res.update(self.echeck_helper.get_status(eventtime))
return res
# DUMP_TMC support
def setup_register_dump(self, read_registers, read_translate=None):
self.read_registers = read_registers
self.read_translate = read_translate
gcode = self.printer.lookup_object("gcode")
gcode.register_mux_command("DUMP_TMC", "STEPPER", self.name,
self.cmd_DUMP_TMC,
desc=self.cmd_DUMP_TMC_help)
cmd_DUMP_TMC_help = "Read and display TMC stepper driver registers"
def cmd_DUMP_TMC(self, gcmd):
logging.info("DUMP_TMC %s", self.name)
reg_name = gcmd.get('REGISTER', None)
if reg_name is not None:
reg_name = reg_name.upper()
val = self.fields.registers.get(reg_name)
if (val is not None) and (reg_name not in self.read_registers):
# write-only register
gcmd.respond_info(self.fields.pretty_format(reg_name, val))
elif reg_name in self.read_registers:
# readable register
val = self.mcu_tmc.get_register(reg_name)
if self.read_translate is not None:
reg_name, val = self.read_translate(reg_name, val)
gcmd.respond_info(self.fields.pretty_format(reg_name, val))
else:
raise gcmd.error("Unknown register name '%s'" % (reg_name))
else:
gcmd.respond_info("========== Write-only registers ==========")
for reg_name, val in self.fields.registers.items():
if reg_name not in self.read_registers:
gcmd.respond_info(self.fields.pretty_format(reg_name, val))
gcmd.respond_info("========== Queried registers ==========")
for reg_name in self.read_registers:
val = self.mcu_tmc.get_register(reg_name)
if self.read_translate is not None:
reg_name, val = self.read_translate(reg_name, val)
gcmd.respond_info(self.fields.pretty_format(reg_name, val))
######################################################################
# TMC virtual pins
######################################################################
# Helper class for "sensorless homing"
class TMCVirtualPinHelper:
def __init__(self, config, mcu_tmc):
self.printer = config.get_printer()
self.mcu_tmc = mcu_tmc
self.fields = mcu_tmc.get_fields()
if self.fields.lookup_register('diag0_stall') is not None:
if config.get('diag0_pin', None) is not None:
self.diag_pin = config.get('diag0_pin')
self.diag_pin_field = 'diag0_stall'
else:
self.diag_pin = config.get('diag1_pin', None)
self.diag_pin_field = 'diag1_stall'
else:
self.diag_pin = config.get('diag_pin', None)
self.diag_pin_field = None
self.mcu_endstop = None
self.en_pwm = False
self.pwmthrs = self.coolthrs = 0
# Register virtual_endstop pin
name_parts = config.get_name().split()
ppins = self.printer.lookup_object("pins")
ppins.register_chip("%s_%s" % (name_parts[0], name_parts[-1]), self)
def setup_pin(self, pin_type, pin_params):
# Validate pin
ppins = self.printer.lookup_object('pins')
if pin_type != 'endstop' or pin_params['pin'] != 'virtual_endstop':
raise ppins.error("tmc virtual endstop only useful as endstop")
if pin_params['invert'] or pin_params['pullup']:
raise ppins.error("Can not pullup/invert tmc virtual pin")
if self.diag_pin is None:
raise ppins.error("tmc virtual endstop requires diag pin config")
# Setup for sensorless homing
self.printer.register_event_handler("homing:homing_move_begin",
self.handle_homing_move_begin)
self.printer.register_event_handler("homing:homing_move_end",
self.handle_homing_move_end)
self.mcu_endstop = ppins.setup_pin('endstop', self.diag_pin)
return self.mcu_endstop
def handle_homing_move_begin(self, hmove):
if self.mcu_endstop not in hmove.get_mcu_endstops():
return
self.pwmthrs = self.fields.get_field("tpwmthrs")
self.coolthrs = self.fields.get_field("tcoolthrs")
reg = self.fields.lookup_register("en_pwm_mode", None)
if reg is None:
# On "stallguard4" drivers, "stealthchop" must be enabled
self.en_pwm = not self.fields.get_field("en_spreadcycle")
tp_val = self.fields.set_field("tpwmthrs", 0)
self.mcu_tmc.set_register("TPWMTHRS", tp_val)
val = self.fields.set_field("en_spreadcycle", 0)
else:
# On earlier drivers, "stealthchop" must be disabled
self.en_pwm = self.fields.get_field("en_pwm_mode")
self.fields.set_field("en_pwm_mode", 0)
val = self.fields.set_field(self.diag_pin_field, 1)
self.mcu_tmc.set_register("GCONF", val)
if self.coolthrs == 0:
tc_val = self.fields.set_field("tcoolthrs", 0xfffff)
self.mcu_tmc.set_register("TCOOLTHRS", tc_val)
def handle_homing_move_end(self, hmove):
if self.mcu_endstop not in hmove.get_mcu_endstops():
return
reg = self.fields.lookup_register("en_pwm_mode", None)
if reg is None:
tp_val = self.fields.set_field("tpwmthrs", self.pwmthrs)
self.mcu_tmc.set_register("TPWMTHRS", tp_val)
val = self.fields.set_field("en_spreadcycle", not self.en_pwm)
else:
self.fields.set_field("en_pwm_mode", self.en_pwm)
val = self.fields.set_field(self.diag_pin_field, 0)
self.mcu_tmc.set_register("GCONF", val)
tc_val = self.fields.set_field("tcoolthrs", self.coolthrs)
self.mcu_tmc.set_register("TCOOLTHRS", tc_val)
######################################################################
# Config reading helpers
######################################################################
# Helper to initialize the wave table from config or defaults
def TMCWaveTableHelper(config, mcu_tmc):
set_config_field = mcu_tmc.get_fields().set_config_field
set_config_field(config, "mslut0", 0xAAAAB554)
set_config_field(config, "mslut1", 0x4A9554AA)
set_config_field(config, "mslut2", 0x24492929)
set_config_field(config, "mslut3", 0x10104222)
set_config_field(config, "mslut4", 0xFBFFFFFF)
set_config_field(config, "mslut5", 0xB5BB777D)
set_config_field(config, "mslut6", 0x49295556)
set_config_field(config, "mslut7", 0x00404222)
set_config_field(config, "w0", 2)
set_config_field(config, "w1", 1)
set_config_field(config, "w2", 1)
set_config_field(config, "w3", 1)
set_config_field(config, "x1", 128)
set_config_field(config, "x2", 255)
set_config_field(config, "x3", 255)
set_config_field(config, "start_sin", 0)
set_config_field(config, "start_sin90", 247)
# Helper to configure and query the microstep settings
def TMCMicrostepHelper(config, mcu_tmc):
fields = mcu_tmc.get_fields()
stepper_name = " ".join(config.get_name().split()[1:])
if not config.has_section(stepper_name):
raise config.error(
"Could not find config section '[%s]' required by tmc driver"
% (stepper_name,))
stepper_config = ms_config = config.getsection(stepper_name)
if (stepper_config.get('microsteps', None, note_valid=False) is None
and config.get('microsteps', None, note_valid=False) is not None):
# Older config format with microsteps in tmc config section
ms_config = config
steps = {256: 0, 128: 1, 64: 2, 32: 3, 16: 4, 8: 5, 4: 6, 2: 7, 1: 8}
mres = ms_config.getchoice('microsteps', steps)
fields.set_field("mres", mres)
fields.set_field("intpol", config.getboolean("interpolate", True))
# Helper for calculating TSTEP based values from velocity
def TMCtstepHelper(step_dist, mres, tmc_freq, velocity):
if velocity > 0.:
step_dist_256 = step_dist / (1 << mres)
threshold = int(tmc_freq * step_dist_256 / velocity + .5)
return max(0, min(0xfffff, threshold))
else:
return 0xfffff
# Helper to configure stealthChop-spreadCycle transition velocity
def TMCStealthchopHelper(config, mcu_tmc, tmc_freq):
fields = mcu_tmc.get_fields()
en_pwm_mode = False
velocity = config.getfloat('stealthchop_threshold', None, minval=0.)
tpwmthrs = 0xfffff
if velocity is not None:
en_pwm_mode = True
stepper_name = " ".join(config.get_name().split()[1:])
sconfig = config.getsection(stepper_name)
rotation_dist, steps_per_rotation = stepper.parse_step_distance(sconfig)
step_dist = rotation_dist / steps_per_rotation
mres = fields.get_field("mres")
tpwmthrs = TMCtstepHelper(step_dist, mres, tmc_freq, velocity)
fields.set_field("tpwmthrs", tpwmthrs)
reg = fields.lookup_register("en_pwm_mode", None)
if reg is not None:
fields.set_field("en_pwm_mode", en_pwm_mode)
else:
# TMC2208 uses en_spreadCycle
fields.set_field("en_spreadcycle", not en_pwm_mode)