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Diffstat (limited to 'Adafruit_Python_MCP3008/Adafruit_MCP3008/MCP3008.py')
| -rw-r--r-- | Adafruit_Python_MCP3008/Adafruit_MCP3008/MCP3008.py | 92 |
1 files changed, 92 insertions, 0 deletions
diff --git a/Adafruit_Python_MCP3008/Adafruit_MCP3008/MCP3008.py b/Adafruit_Python_MCP3008/Adafruit_MCP3008/MCP3008.py new file mode 100644 index 0000000..027cec7 --- /dev/null +++ b/Adafruit_Python_MCP3008/Adafruit_MCP3008/MCP3008.py @@ -0,0 +1,92 @@ +# Copyright (c) 2016 Adafruit Industries +# Author: Tony DiCola +# +# Permission is hereby granted, free of charge, to any person obtaining a copy +# of this software and associated documentation files (the "Software"), to deal +# in the Software without restriction, including without limitation the rights +# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell +# copies of the Software, and to permit persons to whom the Software is +# furnished to do so, subject to the following conditions: +# +# The above copyright notice and this permission notice shall be included in +# all copies or substantial portions of the Software. +# +# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR +# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, +# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE +# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER +# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, +# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN +# THE SOFTWARE. +import Adafruit_GPIO as GPIO +import Adafruit_GPIO.SPI as SPI + + +class MCP3008(object): + """Class to represent an Adafruit MCP3008 analog to digital converter. + """ + + def __init__(self, clk=None, cs=None, miso=None, mosi=None, spi=None, gpio=None): + """Initialize MAX31855 device with software SPI on the specified CLK, + CS, and DO pins. Alternatively can specify hardware SPI by sending an + Adafruit_GPIO.SPI.SpiDev device in the spi parameter. + """ + self._spi = None + # Handle hardware SPI + if spi is not None: + self._spi = spi + elif clk is not None and cs is not None and miso is not None and mosi is not None: + # Default to platform GPIO if not provided. + if gpio is None: + gpio = GPIO.get_platform_gpio() + self._spi = SPI.BitBang(gpio, clk, mosi, miso, cs) + else: + raise ValueError('Must specify either spi for for hardware SPI or clk, cs, miso, and mosi for softwrare SPI!') + self._spi.set_clock_hz(1000000) + self._spi.set_mode(0) + self._spi.set_bit_order(SPI.MSBFIRST) + + def read_adc(self, adc_number): + """Read the current value of the specified ADC channel (0-7). The values + can range from 0 to 1023 (10-bits). + """ + assert 0 <= adc_number <= 7, 'ADC number must be a value of 0-7!' + # Build a single channel read command. + # For example channel zero = 0b11000000 + command = 0b11 << 6 # Start bit, single channel read + command |= (adc_number & 0x07) << 3 # Channel number (in 3 bits) + # Note the bottom 3 bits of command are 0, this is to account for the + # extra clock to do the conversion, and the low null bit returned at + # the start of the response. + resp = self._spi.transfer([command, 0x0, 0x0]) + # Parse out the 10 bits of response data and return it. + result = (resp[0] & 0x01) << 9 + result |= (resp[1] & 0xFF) << 1 + result |= (resp[2] & 0x80) >> 7 + return result & 0x3FF + + def read_adc_difference(self, differential): + """Read the difference between two channels. Differential should be a + value of: + - 0: Return channel 0 minus channel 1 + - 1: Return channel 1 minus channel 0 + - 2: Return channel 2 minus channel 3 + - 3: Return channel 3 minus channel 2 + - 4: Return channel 4 minus channel 5 + - 5: Return channel 5 minus channel 4 + - 6: Return channel 6 minus channel 7 + - 7: Return channel 7 minus channel 6 + """ + assert 0 <= differential <= 7, 'Differential number must be a value of 0-7!' + # Build a difference channel read command. + command = 0b10 << 6 # Start bit, differential read + command |= (differential & 0x07) << 3 # Channel number (in 3 bits) + # Note the bottom 3 bits of command are 0, this is to account for the + # extra clock to do the conversion, and the low null bit returned at + # the start of the response. + resp = self._spi.transfer([command, 0x0, 0x0]) + # Parse out the 10 bits of response data and return it. + result = (resp[0] & 0x01) << 9 + result |= (resp[1] & 0xFF) << 1 + result |= (resp[2] & 0x80) >> 7 + return result & 0x3FF |