pynq.iop.pmod_als — Python productivity for Zynq (Pynq) v1.0

# Source code for pynq.iop.pmod_als

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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