# Copyright (c) 2016, Xilinx, Inc.
# SPDX-License-Identifier: BSD-3-Clause
from . import Pmod_IO
from . import PMOD_DIO_BASEADDR
from . import PMOD_DIO_DATA_OFFSET
[docs]class Pmod_Cable(Pmod_IO):
"""This class can be used for a cable connecting Pmod interfaces.
This class inherits from the Pmod IO class.
Note
----
When 2 Pmods are connected using a cable, the parameter 'cable' decides
whether the cable is a 'loopback' or 'straight' cable.
The default is a straight cable (no internal wire twisting).
For pin mapping, please check the Pmod IO class.
Attributes
----------
microblaze : Pmod
Microblaze processor instance used by this module.
index : int
The index of the Pmod pin, from 0 to 7.
direction : str
Input 'in' or output 'out'.
cable : str
Either 'straight' or 'loopback'.
"""
def __init__(self, mb_info, index, direction, cable):
"""Return a new instance of a Cable object.
Only the cable type is checked during initialization, since all the
other parameters are checked by Pmod IO class.
Parameters
----------
mb_info : dict
A dictionary storing Microblaze information, such as the
IP name and the reset name.
index: int
The index of the pin in a Pmod, from 0 to 7.
direction : str
Input 'in' or output 'out'.
cable : str
Either 'straight' or 'loopback'.
"""
if cable not in ['straight', 'loopback']:
raise ValueError("Cable can only be 'straight', or 'loopback'.")
super().__init__(mb_info, index, direction)
self.cable = cable
[docs] def set_cable(self, cable):
"""Set the type for the cable.
Note
----------
The default cable type is 'straight'. Only straight cable or loop-back
cable can be recognized.
Parameters
----------
cable : str
Either 'straight' or 'loopback'.
Returns
-------
None
"""
if cable not in ['straight', 'loopback']:
raise ValueError("Cable can only be 'straight', or 'loopback'.")
self.cable = cable
[docs] def read(self):
"""Receive the value from the Pmod cable.
This method overrides the read() method in the Pmod IO class.
There are no new `write()` method defined in this class, so
the `read()` will be inherited from Pmod IO class.
Note
----
Only use this function when direction = 'in'.
When two Pmods are connected on the same board, for any received raw
value, a "straignt" cable flips the upper 4 pins and the lower 4 pins:
A Pmod interface <=> Another Pmod interface
{vdd,gnd,3,2,1,0} <=> {vdd,gnd,7,6,5,4}
{vdd,gnd,7,6,5,4} <=> {vdd,gnd,3,2,1,0}
A "loop-back" cable satisfies the following mapping
between two Pmods:
A Pmod interface <=> Another Pmod interface
{vdd,gnd,3,2,1,0} <=> {vdd,gnd,3,2,1,0}
{vdd,gnd,7,6,5,4} <=> {vdd,gnd,7,6,5,4}
Returns
-------
int
The data (0 or 1) on the specified Pmod IO pin.
"""
raw_value = self.read_cmd(PMOD_DIO_BASEADDR + PMOD_DIO_DATA_OFFSET)
if self.cable == 'straight':
if self.index < 4:
return (raw_value >> (self.index+4)) & 0x1
else:
return (raw_value >> (self.index-4)) & 0x1
else:
return (raw_value >> self.index) & 0x1