62 lines
1.8 KiB
Plaintext
62 lines
1.8 KiB
Plaintext
;
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; Copyright (c) 2021 mjcross
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;
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; SPDX-License-Identifier: BSD-3-Clause
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;
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.program nec_carrier_burst
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; Generate bursts of carrier.
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;
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; Repeatedly wait for an IRQ to be set then clear it and generate 21 cycles of
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; carrier with 25% duty cycle
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;
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.define NUM_CYCLES 21 ; how many carrier cycles to generate
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.define BURST_IRQ 7 ; which IRQ should trigger a carrier burst
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.define public TICKS_PER_LOOP 4 ; the number of instructions in the loop (for timing)
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.wrap_target
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set X, (NUM_CYCLES - 1) ; initialise the loop counter
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wait 1 irq BURST_IRQ ; wait for the IRQ then clear it
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cycle_loop:
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set pins, 1 ; set the pin high (1 cycle)
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set pins, 0 [1] ; set the pin low (2 cycles)
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jmp X--, cycle_loop ; (1 more cycle)
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.wrap
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% c-sdk {
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static inline void nec_carrier_burst_program_init(PIO pio, uint sm, uint offset, uint pin, float freq) {
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// Create a new state machine configuration
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//
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pio_sm_config c = nec_carrier_burst_program_get_default_config (offset);
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// Map the SET pin group to one pin, namely the `pin`
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// parameter to this function.
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//
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sm_config_set_set_pins (&c, pin, 1);
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// Set the GPIO function of the pin (connect the PIO to the pad)
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//
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pio_gpio_init (pio, pin);
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// Set the pin direction to output at the PIO
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//
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pio_sm_set_consecutive_pindirs (pio, sm, pin, 1, true);
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// Set the clock divider to generate the required frequency
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//
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float div = clock_get_hz (clk_sys) / (freq * nec_carrier_burst_TICKS_PER_LOOP);
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sm_config_set_clkdiv (&c, div);
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// Apply the configuration to the state machine
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//
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pio_sm_init (pio, sm, offset, &c);
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// Set the state machine running
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//
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pio_sm_set_enabled (pio, sm, true);
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}
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%}
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