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cedargrove_ad5293.py
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cedargrove_ad5293.py
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# SPDX-FileCopyrightText: Copyright (c) 2023 JG for Cedar Grove Maker Studios
#
# SPDX-License-Identifier: MIT
"""
`cedargrove_ad5293`
================================================================================
A CircuitPython driver for the AD5293 digital potentiometer.
* Author(s): JG
Implementation Notes
--------------------
**Hardware:**
* Cedar Grove Studios AD5293 breakout or equivalent
**Software and Dependencies:**
* Adafruit CircuitPython firmware for the supported boards:
https://circuitpython.org/downloads
* Adafruit's Bus Device library: https://github.com/adafruit/Adafruit_CircuitPython_BusDevice
"""
import time
import digitalio
from adafruit_bus_device.spi_device import SPIDevice
__version__ = "0.0.0+auto.0"
__repo__ = "https://github.com/CedarGroveStudios/Cedargrove_CircuitPython_AD5293.git"
class AD5293:
"""Class representing the Cedar Grove AD5293, an SPI digital linear taper
potentiometer breakout module.
The AD5293 Digital Potentiometer is an SPI, 10-bit, 100K-ohm device. The
device operates with a digital logic power source of 2.7v to 5.5v and a
dual analog power source of +/-9v to +/-16.5v. The potentiometer pins act
similarly to a passive resistive potentiometer, but requires that voltages
placed on any of the three pins not exceed the analog power supply voltage.
The CircuitPython driver supports a single SPI potentiometer device per
instance. Connecting the SDO pin to the SPI host input pin is not required
nor recommended since the SDO pin could interfere with other SPI-connected
devices.
This driver does not work with daisy-chained devices.
The Cedar Grove AD5293 custom breakout board provides power and signal
connections for SPI and the potentiometer chip. The AD5293 is also used in
the AD9833-based Cedar Grove Precision VCO Eurorack module."""
def __init__(self, spi=None, select=None, wiper=0):
"""Initialize the AD5293 device instance. During initialization, the
potentiometer is reset, writing is enabled, and the wiper is set to the
specified initialization value.
:param busio.SPI spi: The `busio.SPI` definition. Defaults to None.
:param board select: The chip select pin designation. Defaults to None.
:param int wiper: The initial 10-bit potentiometer wiper integer value,
range from 0 to 1023. Defaults to 0."""
# Define the SPI bus connection
self._spi = spi
chip_sel = digitalio.DigitalInOut(select)
self._device = SPIDevice(
self._spi, chip_sel, baudrate=1000000, polarity=0, phase=1
)
# Power on delay (2ms minimum)
time.sleep(0.03)
# Place device into normal mode (not powered-down)
self._send_data(0x2000)
# Reset the device and disable write-protect
self.reset()
# Set initial wiper value
if wiper < 0 or wiper > 1023:
raise ValueError("Raw wiper value must be from 0 to 1023")
self._wiper = wiper
self._normalized_wiper = self._wiper / 1023.0
self._send_data(0x0400 | wiper)
@property
def wiper(self):
"""The raw value of the potentiometer's wiper."""
return self._wiper
@wiper.setter
def wiper(self, new_wiper=0):
"""Set the raw value of the potentiometer's wiper.
:param new_wiper: The raw wiper value from 0 to 1023."""
if new_wiper < 0 or new_wiper > 1023:
raise ValueError("Raw wiper value must be from 0 to 1023")
self._send_data(0x0400 | int(new_wiper))
self._wiper = new_wiper
@property
def normalized_wiper(self):
"""The normalized value of the potentiometer's wiper."""
return self._normalized_wiper
@normalized_wiper.setter
def normalized_wiper(self, new_norm_wiper):
"""Set the normalized value of the potentiometer's wiper.
:param new_norm_wiper: The normalized wiper value from 0.0 to 1.0."""
if new_norm_wiper < 0 or new_norm_wiper > 1.0:
raise ValueError("Normalized wiper value must be from 0.0 to 1.0")
self._send_data(0x0400 | int(new_norm_wiper * 1023.0))
self._normalized_wiper = new_norm_wiper
def shutdown(self):
"""Connects the W pin to the B pin and opens the A pin. The content
of the wiper register is not changed."""
self._send_data(0x2001)
def reset(self):
"""Reset the potentiometer. Refresh RDAC with mid-scale value. Disable
write-protect."""
self._send_data(0x1000) # Reset
time.sleep(0.002) # Reset delay (1.5ms min)
self._send_data(0x1802) # Disable write-protect
def _send_data(self, data):
"""Send a 16-bit word through SPI bus as two 8-bit bytes.
:param int data: The 16-bit data value to write to the SPI device."""
with self._device:
self._spi.write(bytes([data >> 8, data & 0xFF]))