def _set_dac_value(self, channel, value):
        '''Write DAC
        '''
        # DAC value cannot be -128
        if value == -128:
            value = -127
        if value < 0:
            sign = 1
        else:
            sign = 0
        value = (sign << 7) | (0x7F & abs(value))
        self._intf.write(self._base_addr + self.DS_4424_ADD, array('B', pack('BB', channel, value)))
Write DAC