93 lines
2.6 KiB
Python
93 lines
2.6 KiB
Python
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'''
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Circuit Python wrapper around PIO implementation of UART
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Original source of these examples: https://github.com/adafruit/Adafruit_CircuitPython_PIOASM/tree/main/examples (MIT)
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'''
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import rp2pio
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from array import array
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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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; compiles to:
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'''
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tx_code = array('H', [40864, 63271, 24577, 1602])
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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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; compiles to:
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'''
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rx_code = array('H', [8224, 59943, 16385, 1602])
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class PIO_UART:
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def __init__(self, *, tx, rx, baudrate=9600):
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if tx:
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self.tx_pio = rp2pio.StateMachine(
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tx_code,
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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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sideset_enable=True,
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)
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if rx:
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self.rx_pio = rp2pio.StateMachine(
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rx_code,
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first_in_pin=rx,
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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.tx_pio.frequency // 8
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@baudrate.setter
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def baudrate(self, frequency):
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self.tx_pio.frequency = frequency * 8
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self.rx_pio.frequency = frequency * 8
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def write(self, buf):
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return self.tx_pio.write(buf)
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@property
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def in_waiting(self):
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return self.rx_pio.in_waiting
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def read(self, n):
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b = bytearray(n)
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n = self.rx_pio.readinto(b)
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return b[:n]
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def readinto(self, buf):
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return self.rx_pio.readinto(buf)
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