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

# Source code for pynq.iop.pmod_dpot

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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_DPOT_PROGRAM = "pmod_dpot.bin"

    class Pmod_DPOT(object):
        """This class controls a digital potentiometer Pmod.

        The Pmod DPOT (PB 200-239) is a digital potentiometer powered by the
        AD5160. Users may set a desired resistance between 60 ~ 10k ohms.

        Attributes
        ----------
        iop : _IOP
            I/O processor instance used by DPOT
        mmio : MMIO
            Memory-mapped I/O instance to read and write instructions and data.

        """
        def __init__(self, if_id):
            """Return a new instance of a DPOT 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_DPOT_PROGRAM)
            self.mmio = self.iop.mmio

            self.iop.start()

        def write(self, val, step=0, log_ms=0):
            """Write the value into the DPOT.

            This method will write the parameters "value", "step", and "log_ms"
            all together into the DPOT Pmod. The parameter "log_ms" is only used
            for debug; users can ignore this parameter.

            Parameters
            ----------
            val : int
                The initial value to start, in [0, 255].
            step : int
                The number of steps when ramping up to the final value.
            log_ms : int
                The length of the log in milliseconds, for debug only.

            Returns
            -------
            None

            """
            if not 0<=val<=255:
                raise ValueError("Initial value should be in range [0, 255].")
            if not 0<=step<=(255-val):
                raise ValueError("Ramp steps should be in range [0, {}]."\
                                .format(255-val))
            if log_ms<0:
                raise ValueError("Requested log_ms value cannot be less than 0.")

            self.mmio.write(iop_const.MAILBOX_OFFSET+\
                            iop_const.MAILBOX_PY2IOP_CMD_OFFSET, 1)

            self.mmio.write(iop_const.MAILBOX_OFFSET, val)
            self.mmio.write(iop_const.MAILBOX_OFFSET+4, step)
            self.mmio.write(iop_const.MAILBOX_OFFSET+8, log_ms)

            if step == 0:
                self.mmio.write(iop_const.MAILBOX_OFFSET+\
                                iop_const.MAILBOX_PY2IOP_CMD_OFFSET, 3)
            else:
                self.mmio.write(iop_const.MAILBOX_OFFSET+\
                                iop_const.MAILBOX_PY2IOP_CMD_OFFSET, 5)

        def _read_hex(self, addr_offset):
            """Read Hex value from Microblaze address space.

            Note
            ----
            This method should not be used directly. It should be only used for
            debug.

            Parameters
            ----------
            addr_offset : int
                The MMIO address to be read from.

            Returns
            -------
            str
                The data read from the MMIO address expressed in hex.

            """
            return hex(self.mmio.read(addr_offset))