ST Spin Family Interface

A Python library for interfacing with ST Spin Family devices, specifically the ST Micro L6470, L6472, L6474, and L6480 ICs. Can be used nearly without modification with similar ICs.

If you do not specify your own spi_transfer function when creating a SpinChain, this project relies on spidev's SPI transfer function.

Python 3.6 or greater recommended.

Getting Started

pip install st-spin or

pip install st-spin[spidev] if you intend to use /dev/spi and spidev's spi transfer function

Add imports

import time  # Used in our example

from stspin import (
    SpinChain,
    SpinDevice,
    Constant as StConstant,
    Register as StRegister,
    utility,
)

Create a device chain

stChain = SpinChain(
    total_devices=2,
    spi_select=(0, 0),
)

This assumes the spi device is at 0, 0.

Create devices

motorMain = stChain.create(1)
motorAux = stChain.create(0)

# Unless you absolutely need holding current,
# it is good practice to disable the power bridges
motorMain.hiZHard()
motorAux.hiZHard()

Run basic commands

motorMain.setRegister(StRegister.SpeedMax, 0x22)

motorMain.run(100)
time.sleep(3)
motorMain.hiZSoft()
time.sleep(1)

# {{{ Set some registers
motorMain.setRegister(StRegister.Acc, 0x5)
motorMain.setRegister(StRegister.Dec, 0x10)
motorAux.setRegister(StRegister.Acc, 0x20)
# }}}

# {{{ Go n steps with both motors
motorMain.move(steps=420000)
motorAux.move(steps=420000)
while motorMain.isBusy():
    time.sleep(0.2)
# }}}

# {{{ Head back
motorMain.setDirection(StConstant.DirReverse)
motorMain.move(steps=420000)
while motorMain.isBusy():
    time.sleep(0.2)
# }}}

# Release holding current
motorAux.hiZHard()
motorMain.hiZHard()

More details

For details on the SPI setup, see create() in spin_chain.py. See example.py.

Creating your own spi_transfer function You may use your own spi transfer function in place of spidev's xfer2.

def custom_spi_transfer(buffer: List[int]) -> List[int]:
    # TODO: Implement me
    pass
    
stChain = SpinChain(
    total_devices=2,
    spi_transfer=custom_spi_transfer,
)

custom_spi_transfer() must take a list of bytes as int, and return a same-length list of bytes as int from the MISO pin.

It should handle latching using the Chip Select pin, and transfer data with MSB first in SPI Mode 3 (sample on rising edge, shift out on falling edge).

On these devices, Chip Select is active low.

Troubleshooting

getStatus() is your friend. Feel free to use getPrettyStatus() under utility.py. The manual is also your friend.

Q: Why is my motor stalling, loud, or both? Most likely the Back-EMF compensation is not configured properly. The correction parameters depend heavily on your motor's ke value (V/Hz), inductance, and phase resistance.

After calculating the parameters using the manufacturer's tool, set KvalAcc, SpeedInt, SlpSt, etc. using setRegister().