32 lines
1.0 KiB
Plaintext
32 lines
1.0 KiB
Plaintext
;
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; Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
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;
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; SPDX-License-Identifier: BSD-3-Clause
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;
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; Side-set pin 0 is used for PWM output
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.program pwm
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.side_set 1 opt
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pull noblock side 0 ; Pull from FIFO to OSR if available, else copy X to OSR.
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mov x, osr ; Copy most-recently-pulled value back to scratch X
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mov y, isr ; ISR contains PWM period. Y used as counter.
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countloop:
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jmp x!=y noset ; Set pin high if X == Y, keep the two paths length matched
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jmp skip side 1
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noset:
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nop ; Single dummy cycle to keep the two paths the same length
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skip:
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jmp y-- countloop ; Loop until Y hits 0, then pull a fresh PWM value from FIFO
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% c-sdk {
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static inline void pwm_program_init(PIO pio, uint sm, uint offset, uint pin) {
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pio_gpio_init(pio, pin);
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pio_sm_set_consecutive_pindirs(pio, sm, pin, 1, true);
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pio_sm_config c = pwm_program_get_default_config(offset);
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sm_config_set_sideset_pins(&c, pin);
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pio_sm_init(pio, sm, offset, &c);
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}
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%}
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