54 lines
1.3 KiB
Python
54 lines
1.3 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.Program(
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"""
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.program uart_tx
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.side_set 1 opt
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; An 8n1 UART transmit program.
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; OUT pin 0 and side-set pin 0 are both mapped to UART TX pin.
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pull side 1 [7] ; Assert stop bit, or stall with line in idle state
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set x, 7 side 0 [7] ; Preload bit counter, assert start bit for 8 clocks
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bitloop: ; This loop will run 8 times (8n1 UART)
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out pins, 1 ; Shift 1 bit from OSR to the first OUT pin
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jmp x-- bitloop [6] ; Each loop iteration is 8 cycles.
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"""
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)
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class TXUART:
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def __init__(self, *, tx, baudrate=9600):
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self.pio = rp2pio.StateMachine(
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code.assembled,
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first_out_pin=tx,
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first_sideset_pin=tx,
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frequency=8 * baudrate,
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initial_sideset_pin_state=1,
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initial_sideset_pin_direction=1,
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initial_out_pin_state=1,
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initial_out_pin_direction=1,
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**code.pio_kwargs,
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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):
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self.pio.frequency = frequency * 8
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def write(self, buf):
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return self.pio.write(buf)
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