# I2C address of the device
MCP3428_DEFAULT_ADDRESS                = 0x68

# MCP3428 Configuration Command Set
MCP3428_CMD_NEW_CNVRSN                = 0x80 # Initiate a new conversion(One-Shot Conversion mode only)
CHANNEL = {
    1: 0x00, # Channel-1 Selected
    2: 0x20, # Channel-2 Selected
    3: 0x40, # Channel-3 Selected
    4: 0x60 # Channel-4 Selected
}

MCP3428_CMD_MODE_CONT                = 0x10 # Continuous Conversion Mode
MCP3428_CMD_MODE_ONESHOT            = 0x00 # One-Shot Conversion Mode
RESOLUTION = {
    12: 0x00, # 240 SPS (12-bit)
    14: 0x04, # 60 SPS (14-bit)
    16:  0x08 # 15 SPS (16-bit)
}

GAIN = {
    1: 0x00, # PGA Gain = 1V/V
    2: 0x01, # PGA Gain = 2V/V
    4: 0x02, # PGA Gain = 4V/V
    8: 0x03 # PGA Gain = 8V/V
}
MCP3428_CMD_READ_CNVRSN                = 0x00 # Read Conversion Result Data

import smbus2 as smbus
from ..api.i2c_handler import I2CDevice

class MCP3428(I2CDevice):
    default_address = MCP3428_DEFAULT_ADDRESS

    def initialize(self, address: int):
        self.bus = smbus.SMBus(1)
        self.address = address

    def config_channel(self, channel: int, gain=1, resolution=12):
        """Select the Configuration Command from the given provided values"""
        self.gain = gain
        self.resolution = resolution
        CONFIG_CMD = (MCP3428_CMD_MODE_CONT | RESOLUTION[resolution] | GAIN[gain] | CHANNEL[channel])
        self.bus.write_byte(self.address, CONFIG_CMD)

    def read_value(self) -> float:
        raw_adc = self._read_adc()
        res_per_bit = 2.048/2**(self.resolution-1)
        return raw_adc*res_per_bit/self.gain

    def _read_adc(self):
        """Read data back from MCP3428_CMD_READ_CNVRSN(0x00), 2 bytes
        raw_adc MSB, raw_adc LSB"""
        read = smbus.i2c_msg.read(self.address, 2)
        self.bus.i2c_rdwr(read)
        data = list(read)
        # Convert the data to 12-bits
        raw_adc = ((data[0] & 0x0F) * 256) + data[1]
        if raw_adc > 2047:
            raw_adc -= 4095
        return raw_adc