ticlib

ticlib is a pure-Python library to drive Pololu Tic stepper motor controllers.

This library supports serial, I²C, and USB connections for Python3; and serial and I²C for Micropython.

Example code

from src.ticlib import TicUSB
from time import sleep

tic = TicUSB()

tic.halt_and_set_position(0)
tic.energize()
tic.exit_safe_start()

positions = [500, 300, 800, 0]
for position in positions:
    tic.set_target_position(position)
    while tic.get_current_position() != tic.get_target_position():
        sleep(0.1)

tic.deenergize()
tic.enter_safe_start()

Installation

The ticlib library is hosted on PyPI and can be installed by running this command:

pip install ticlib

Available controllers

Serial

Example using Python 3 and the pyserial library:

import serial
from src.ticlib import TicSerial

port = serial.Serial("/dev/ttyS0", baud_rate=9600, timeout=0.1, write_timeout=0.1)
tic = TicSerial(port)

Example using Micropython:

from machine import UART
from ticlib import TicSerial

port = UART(0, baudrate=9600, timeout=100)
tic = TicSerial(port)

Instantiation parameters for TicSerial:

• port (required): Serial port used to communicate with the Tic.
• device_number (optional): Number of the device that you want to control. Use this if you have multiple devices connected to your serial line. Defaults to None.
• crc_for_commands (optional): If True, the library will append a CRC byte to every command sent to the Tic. Set this to True if your Tic's "Enable CRC for commands" setting is turned on. Defaults to False.
• crc_for_responses (optional): If True, the library will expect a CRC byte at the end of every response returned by the Tic. Set this to True if your Tic's "Enable CRC for responses" setting is turned on. Defaults to False.

For more details, see Pololu's official documentation on serial command encoding.

I²C

Example using Python 3 and the smbus2 library.

from smbus2 import SMBus
from ticlib import TicI2C, SMBus2Backend

bus = SMBus(3)  # Represents /dev/i2c-3
address = 14    # Address of the Tic, that is its device number
backend = SMBus2Backend(bus)

tic = TicI2C(backend)

Example using Micropython:

from machine import I2C
from ticlib import TicI2C, MachineI2CBackend

i2c = I2C(1)  # ID of your I2C peripheral
address = 14  # Address of the Tic, that is its device number
backend = MachineI2CBackend(i2c, address)

tic = TicI2C(backend)

Instantiation parameter for TicI2C:

• backend (required): The I²C backend. Available options are SMBus2Backend for Python 3 and MachineI2C for Micropython.

Note: If you use a Raspberry Pi, make sure to follow the workaround described in the Pololu documentation.

For more details, see Pololu's official documentation on I²C command encoding.

USB

The USB controller has a dependency on the pyusb library.

Example:

from src.ticlib import TicUSB

tic = TicUSB()

Instantiation parameters for TicUSB:

• product (optional): USB product ID for your Tic. If None, the device will be automatically detected. Use this if multiple Tic devices are connected to your computer. The available options are: TIC_T825 (0x00b3), TIC_T834 (0x00b5), TIC_T500 (0x00bd), TIC_N825 (0x00c3), TIC_T249 (0x00c9), and TIC_36v4 (0x00cb). Defaults to None.
• serial_number (optional): The serial number (in string format) of your Tic. If None, the device will be automatically detected. Use this if multiple Tic devices are connected to your computer. Default to None.

For more details, see Pololu's official documentation on USB command encoding.

Commands:

Available commands:

tic.clear_driver_error()
tic.deenergize()
tic.energize()
tic.enter_safe_start()
tic.exit_safe_start()
tic.go_home(value)
tic.halt_and_hold()
tic.halt_and_set_position(value)
tic.reset()
tic.reset_command_timeout()
tic.set_agc_option(value)
tic.set_current_limit(value)
tic.set_decay_mode(value)
tic.set_max_acceleration(value)
tic.set_max_deceleration(value)
tic.set_max_speed(value)
tic.set_starting_speed(value)
tic.set_step_mode(value)
tic.set_target_position(value)
tic.set_target_velocity(value)

For more details, see the official command reference.

Variables

Available variables:

# General status  -------------------------------------
tic.get_error_occured()
tic.get_error_status()
tic.get_misc_flags()
tic.get_operation_state()

# Step planning ---------------------------------------
tic.get_acting_target_position()
tic.get_current_position()
tic.get_current_velocity()
tic.get_max_acceleration()
tic.get_max_deceleration()
tic.get_max_speed()
tic.get_planning_mode()
tic.get_starting_speed()
tic.get_target_position()
tic.get_target_velocity()
tic.get_time_since_last_step()

# Other -----------------------------------------------
tic.get_analog_reading_rx()
tic.get_analog_reading_scl()
tic.get_analog_reading_sda()
tic.get_analog_reading_tx()
tic.get_current_limit()
tic.get_decay_mode()
tic.get_device_reset()
tic.get_digital_readings()
tic.get_encoder_position()
tic.get_input_after_averaging()
tic.get_input_after_hysteresis()
tic.get_input_after_scaling()
tic.get_input_state()
tic.get_pin_states()
tic.get_rc_pulse()
tic.get_step_mode()
tic.get_vin_voltage()
tic.get_uptime()

# T249-only -------------------------------------------
tic.get_agc_bottom_current_limit()
tic.get_agc_current_boost_steps()
tic.get_agc_frequency_limit()
tic.get_agc_mode()
tic.get_last_motor_driver_error()

# 36v4-only -------------------------------------------
tic.get_last_hp_driver_errors()

For more details, see the official variable reference.

Settings

Available settings:

tic.settings.get_control_mode()

# Miscellaneous -------------------------------------------------
tic.settings.get_auto_clear_driver_error()
tic.settings.get_disable_safe_start()
tic.settings.get_ignore_err_line_high()
tic.settings.get_never_sleep()
tic.settings.get_vin_calibration()

# Soft error response -------------------------------------------
tic.settings.get_current_limit_during_error()
tic.settings.get_soft_error_position()
tic.settings.get_soft_error_response()

# Serial --------------------------------------------------------
tic.settings.get_serial_7bit_responses()
tic.settings.get_serial_14bit_device_number()
tic.settings.get_serial_alt_device_number()
tic.settings.get_serial_baud_rate()
tic.settings.get_serial_command_timeout()
tic.settings.get_serial_crc_for_commands()
tic.settings.get_serial_crc_for_responses()
tic.settings.get_serial_device_number()
tic.settings.get_serial_enable_alt_device_number()
tic.settings.get_serial_response_delay()

# Encoder -------------------------------------------------------
tic.settings.get_encoder_postscaler()
tic.settings.get_encoder_prescaler()
tic.settings.get_encoder_unlimited()

# Input conditioning --------------------------------------------
tic.settings.get_input_averaging_enabled()
tic.settings.get_input_hysteresis()

# RC and analog scaling -----------------------------------------
tic.settings.get_input_invert()
tic.settings.get_input_max()
tic.settings.get_input_min()
tic.settings.get_input_neutral_max()
tic.settings.get_input_neutral_min()
tic.settings.get_input_scaling_degree()
tic.settings.get_output_max()
tic.settings.get_output_min()

# Pin Configuration ---------------------------------------------
# SCL
tic.settings.get_scl_active_high()
tic.settings.get_scl_config()
tic.settings.get_scl_enable_analog()
tic.settings.get_scl_enable_pull_up()
tic.settings.get_scl_kill_switch()
tic.settings.get_scl_limit_switch_forward()
tic.settings.get_scl_limit_switch_reverse()
tic.settings.get_scl_pin_function()
# SDA
tic.settings.get_sda_active_high()
tic.settings.get_sda_config()
tic.settings.get_sda_enable_analog()
tic.settings.get_sda_enable_pull_up()
tic.settings.get_sda_kill_switch()
tic.settings.get_sda_limit_switch_forward()
tic.settings.get_sda_limit_switch_reverse()
tic.settings.get_sda_pin_function()
# TX
tic.settings.get_tx_active_high()
tic.settings.get_tx_config()
tic.settings.get_tx_enable_analog()
tic.settings.get_tx_kill_switch()
tic.settings.get_tx_limit_switch_forward()
tic.settings.get_tx_limit_switch_reverse()
tic.settings.get_tx_pin_function()
# RX
tic.settings.get_rx_active_high()
tic.settings.get_rx_config()
tic.settings.get_rx_enable_analog()
tic.settings.get_rx_kill_switch()
tic.settings.get_rx_limit_switch_forward()
tic.settings.get_rx_limit_switch_reverse()
tic.settings.get_rx_pin_function()
# RC
tic.settings.get_rc_active_high()
tic.settings.get_rc_config()
tic.settings.get_rc_kill_switch()
tic.settings.get_rc_limit_switch_forward()
tic.settings.get_rc_limit_switch_reverse()

# Motor ---------------------------------------------------------
tic.settings.get_current_limit()
tic.settings.get_decay_mode()
tic.settings.get_invert_motor_direction()
tic.settings.get_max_acceleration()
tic.settings.get_max_deceleration()
tic.settings.get_max_speed()
tic.settings.get_starting_speed()
tic.settings.get_step_mode()

# Homing --------------------------------------------------------
tic.settings.get_auto_homing()
tic.settings.get_auto_homing_forward()
tic.settings.get_homing_speed_away()
tic.settings.get_homing_speed_towards()

# T249-only -----------------------------------------------------
tic.settings.get_agc_bottom_current_limit()
tic.settings.get_agc_current_boost_steps()
tic.settings.get_agc_mode()
tic.settings.get_agc_frequency_limit()

# 36v4-only -----------------------------------------------------
tic.settings.get_hp_current_trip_blanking_time()
tic.settings.get_hp_decay_mode()
tic.settings.get_hp_enable_adaptive_blanking_time()
tic.settings.get_hp_enable_unrestricted_current_limits()
tic.settings.get_hp_fixed_off_time()
tic.settings.get_hp_mixed_decay_transition_time()

Modifying settings is currently not supported.

For more details, see the official settings reference.

Version history

0.2.2 (May 14, 2021)

• Fixed some bugs for Micropython

0.2.1 (May 4, 2021)

• Issue #1: Fixed bug that prevented multiple Tic controllers from working at the same time.

0.2.0 (April 20, 2021)

• Added support for Micropython with serial and I2C.

0.1.0 (April 18, 2021)

Initial release.

Running the tests

For Python:

docker run -it -v ${PWD}:/base -w /base python python /base/tests/tests.py

For Micropython:

docker run -it -v ${PWD}:/base -w /base mitchins/micropython-linux micropython /base/tests/tests.py

Notes for project maintainers

To release a new version of this library:

• Update version number in src/ticlib/__init__.py
• Add release notes in the "Version history" section above.
• Create and push tag of the form: v<VERSION_NUMBER> (e.g. v.0.2.1)
• Delete existing dist/ directory, if any.
• Run: python3 -m build
• Run: python3 -m twine upload dist/*