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__author__      = "Cathal McCabe, Yun Rock Qu"
__copyright__   = "Copyright 2016, Xilinx"
__email__       = "pynq_support@xilinx.com"


import time
from pynq import MMIO
from pynq.iop import request_iop
from pynq.iop import iop_const
from pynq.iop import PMODA
from pynq.iop import PMODB

PMOD_ALS_PROGRAM = "pmod_als.bin"
PMOD_ALS_LOG_START = iop_const.MAILBOX_OFFSET+16
PMOD_ALS_LOG_END = PMOD_ALS_LOG_START+(1000*4)

class Pmod_ALS(object):
    """This class controls a light sensor Pmod.
    
    The Digilent Pmod ALS demonstrates light-to-digital sensing through a
    single ambient light sensor. This is based on an ADC081S021 analog-to-digital
    converter and a TEMT6000X01 ambient light sensor.

    Attributes
    ----------
    iop : _IOP
        I/O processor instance used by ALS
    mmio : MMIO
        Memory-mapped I/O instance to read and write instructions and data.
    log_interval_ms : int
        Time in milliseconds between sampled reads of the ALS sensor
        
    """
    def __init__(self, if_id):
        """Return a new instance of an ALS object. 
        
        Parameters
        ----------
        if_id : int
            The interface ID (1, 2) corresponding to (PMODA, PMODB).
            
        """
        if not if_id in [PMODA, PMODB]:
            raise ValueError("No such IOP for Pmod device.")
            
        self.iop = request_iop(if_id, PMOD_ALS_PROGRAM)
        self.mmio = self.iop.mmio
        self.log_interval_ms = 1000
        
        self.iop.start()
        
    def read(self):
        """Read current light value measured by the ALS Pmod.
        
        Parameters
        ----------
        None
        
        Returns
        -------
        int
            The current sensor value.
        
        """
        self.mmio.write(iop_const.MAILBOX_OFFSET+\
                        iop_const.MAILBOX_PY2IOP_CMD_OFFSET, 3)      
        while (self.mmio.read(iop_const.MAILBOX_OFFSET+\
                                iop_const.MAILBOX_PY2IOP_CMD_OFFSET) == 3):
            pass
        return self.mmio.read(iop_const.MAILBOX_OFFSET)

    def set_log_interval_ms(self,log_interval_ms):
        """Set the length of the log in the ALS Pmod.
        
        This method can set the length of the log, so that users can read out
        multiple values in a single log. 
        
        Parameters
        ----------
        log_interval_ms : int
            The length of the log in milliseconds, for debug only.
            
        Returns
        -------
        None
        
        """
        if (log_interval_ms < 0):
            raise ValueError("Log length should not be less than 0.")
        
        self.log_interval_ms = log_interval_ms
        self.mmio.write(iop_const.MAILBOX_OFFSET+4, self.log_interval_ms)

    def start_log(self):
        """Start recording multiple values in a log.
        
        This method will first call set_log_interval_ms() before writting to
        the MMIO.
        
        Parameters
        ----------
        None
            
        Returns
        -------
        None
        
        """
        self.set_log_interval_ms(self.log_interval_ms)
        self.mmio.write(iop_const.MAILBOX_OFFSET+\
                        iop_const.MAILBOX_PY2IOP_CMD_OFFSET, 7)

    def stop_log(self):
        """Stop recording multiple values in a log.
        
        Simply write to the MMIO to stop the log.
        
        Parameters
        ----------
        None
            
        Returns
        -------
        None
        
        """
        self.mmio.write(iop_const.MAILBOX_OFFSET+\
                        iop_const.MAILBOX_PY2IOP_CMD_OFFSET, 1)

    def get_log(self):
        """Return list of logged samples.
        
        Parameters
        ----------
        None
            
        Returns
        -------
        List of valid samples from the ALS sensor [0-255]
        
        """
        # Stop logging
        self.stop_log()

        # Prep iterators and results list
        head_ptr = self.mmio.read(iop_const.MAILBOX_OFFSET+0x8)
        tail_ptr = self.mmio.read(iop_const.MAILBOX_OFFSET+0xC)
        readings = []

        # Sweep circular buffer for samples
        if head_ptr == tail_ptr:
            return None
        elif head_ptr < tail_ptr:
            for i in range(head_ptr,tail_ptr,4):
                readings.append(self.mmio.read(i))
        else:
            for i in range(head_ptr,PMOD_ALS_LOG_END,4):
                readings.append(self.mmio.read(i))
            for i in range(PMOD_ALS_LOG_START,tail_ptr,4):
                readings.append(self.mmio.read(i)) 

        return readings


     
