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130 lines
3.5 KiB
130 lines
3.5 KiB
import logging
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from cocotb.triggers import FallingEdge, RisingEdge, Timer, ReadOnly
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class Uart:
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"""UART base class"""
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def __init__(self, txrx, clock, div, bits, parity, *args, **kwargs):
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self._version = "0.0.1"
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self.log = logging.getLogger(f"cocotb.{txrx._path}")
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self._txrx = txrx
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self._clock = clock
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self._div = div
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self._bits = bits
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self._par = parity
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self._clkedge = RisingEdge(self._clock)
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async def _wait_cycle(self):
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for x in range(self._div):
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await self._clkedge
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@staticmethod
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def odd_parity(data):
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parity = True
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while data:
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parity = not parity
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data = data & (data - 1)
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return int(parity)
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class UartReceiver(Uart):
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def __init__(self, txrx, clock, div, bits, parity, *args, **kwargs):
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super().__init__(txrx, clock, div, bits, parity, *args, **kwargs)
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self.log.info("UART receiver")
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self.log.info(" cocotbext-uart version %s", self._version)
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self.log.info(" Copyright (c) 2022 Torsten Meissner")
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async def receive(self):
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"""Receive and return one UART frame"""
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# Wait for frame start
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await FallingEdge(self._txrx)
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# Consume start bit
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await self._get_start_bit()
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# Receive data bits
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self._rec = 0
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for x in range(self._bits):
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await self._wait_cycle()
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await ReadOnly()
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self._rec |= bool(self._txrx.value.integer) << x
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if self._par:
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# Consume parity bit
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await self._get_parity_bit()
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# Consume stop bit
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await self._get_stop_bit()
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self.log.info("Received data: %s", hex(self._rec))
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return self._rec
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async def _get_start_bit(self):
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"""Consume and check start bit"""
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for x in range(int(self._div/2)):
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await self._clkedge
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await ReadOnly()
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if self._txrx.value == 1:
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self.log.warning("Start bit set")
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async def _get_stop_bit(self):
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"""Consume and check stop bit"""
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await self._wait_cycle()
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await ReadOnly()
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if self._txrx.value == 0:
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self.log.warning("Stop bit not set")
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async def _get_parity_bit(self):
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"""Consume and check parity bit"""
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await self._wait_cycle()
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await ReadOnly()
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if self.odd_parity(self._rec) != self._txrx.value:
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self.log.warning("Parity wrong")
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class UartDriver(Uart):
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def __init__(self, txrx, clock, div, bits, parity, *args, **kwargs):
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super().__init__(txrx, clock, div, bits, parity, *args, **kwargs)
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self.log.info("UART sender")
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self.log.info(" cocotbext-uart version %s", self._version)
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self.log.info(" Copyright (c) 2022 Torsten Meissner")
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# Drive input defaults (setimmediatevalue to avoid x asserts)
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self._txrx.setimmediatevalue(1)
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async def send(self, data):
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"""Send one UART frame"""
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self._data = data;
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self.log.info("Sending data: %s", hex(self._data))
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# Send start bit
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await self._send_bit(0)
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# Send data bits
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for x in range(self._bits):
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self._txrx.value = (self._data >> x) & 1
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await self._wait_cycle()
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if self._par:
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# Send parity bit
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await self._send_bit(self.odd_parity(self._data))
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# Consume stop bit
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await self._send_bit(1)
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async def _send_bit(self, data):
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self._txrx.value = data
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await self._wait_cycle()
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