MCP3208

"""
Source: https://github.com/MomsFriendlyRobotCompany/mcp3208

I removed the Adafruit dependency and added a context manager.
Don't forget to activate SPI on your Raspberry Pi
"""

from spidev import SpiDev


class MCP3208:
    def __init__(self, bus=0, device=0, vref=3.3):
        """
        bus := The spi bus where MCP3208 is attached to
        device := Device selection
        vref := reference voltage
        """
        self.spi = SpiDev(bus, device)
        self.spi.max_speed_hz = 1000000
        self.vref = vref

    def __del__(self):
        self.spi.close()

    def __enter__(self):
        return self

    def __exit__(self, exc_type, exc_obj, exc_tb):
        self.spi.close()

    def read(self, channel):
        if not 0 <= channel <= 7:
            raise Exception(f"MCP3208 channel must be 0-7: {channel}")

        cmd = 128  # 1000 0000
        cmd += 64  # 1100 0000
        cmd += (channel & 0x07) << 3
        ret = self.spi.xfer2([cmd, 0x0, 0x0])

        # get the 12b out of the return
        val = (ret[0] & 0x01) << 11  # only B11 is here
        val |= ret[1] << 3  # B10:B3
        val |= ret[2] >> 5  # MSB has B2:B0 ... need to move down to LSB

        return (val & 0x0FFF) / 4096 * self.vref  # ensure we are only sending 12b