59 lines
1.5 KiB
Python
59 lines
1.5 KiB
Python
# SPDX-FileCopyrightText: 2021 Jeff Epler, written for Adafruit Industries
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#
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# SPDX-License-Identifier: MIT
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import rp2pio
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import adafruit_pioasm
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code = adafruit_pioasm.assemble(
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"""
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.program uart_rx_mini
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; Minimum viable 8n1 UART receiver. Wait for the start bit, then sample 8 bits
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; with the correct timing.
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; IN pin 0 is mapped to the GPIO used as UART RX.
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; Autopush must be enabled, with a threshold of 8.
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wait 0 pin 0 ; Wait for start bit
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set x, 7 [10] ; Preload bit counter, delay until eye of first data bit
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bitloop: ; Loop 8 times
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in pins, 1 ; Sample data
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jmp x-- bitloop [6] ; Each iteration is 8 cycles
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"""
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)
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class RXUART:
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def __init__(self, pin, baudrate=9600):
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self.pio = rp2pio.StateMachine(
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code,
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first_in_pin=pin,
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frequency=8 * baudrate,
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auto_push=True,
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push_threshold=8,
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)
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@property
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def timeout(self):
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return 0
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@property
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def baudrate(self):
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return self.pio.frequency // 8
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@baudrate.setter
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def baudrate(self, frequency): # pylint: disable=unused-argument
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self.pio.frequency = freqency * 8 # pylint: disable=undefined-variable
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@property
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def in_waiting(self):
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return self.pio.in_waiting
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def read(self, n):
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b = bytearray(n)
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n = self.pio.readinto(b)
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return b[:n]
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def readinto(self, buf): # pylint: disable=unused-argument
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return self.pio.readinto(n) # pylint: disable=undefined-variable
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