mirror of
https://github.com/arabine/open-story-teller.git
synced 2025-12-06 17:09:06 +01:00
62 lines
2 KiB
Text
62 lines
2 KiB
Text
; i2s.pio
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;
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.program i2s_out_master
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; I2S audio output block. Synchronous with clock and input.
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; Must run at BCK * 2.
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;
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; This block also outputs the word clock (also called frame or LR clock) and
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; the bit clock.
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;
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; Set register x to (bit depth - 2) (e.g. for 24 bit audio, set to 22).
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; Note that if this is needed to be synchronous with the SCK module,
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; it is not possible to run 24-bit frames with an SCK of 256x fs. You must either
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; run SCK at 384x fs (if your codec permits this) or use 32-bit frames, which
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; work fine with 24-bit codecs.
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.side_set 2
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public entry_point:
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; /--- LRCLK
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; |/-- BCLK
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frameL: ; ||
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set x, 30 side 0b00 ; start of Left frame
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pull noblock side 0b01 ; One clock after edge change with no data
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dataL:
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out pins, 1 side 0b00
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jmp x-- dataL side 0b01
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frameR:
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set x, 30 side 0b10
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pull noblock side 0b11 ; One clock after edge change with no data
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dataR:
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out pins, 1 side 0b10
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jmp x-- dataR side 0b11
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% c-sdk {
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// These constants are the I2S clock to pio clock ratio
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const int i2s_sck_program_pio_mult = 2;
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const int i2s_out_master_program_pio_mult = 2;
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static inline void i2s_out_master_program_init(PIO pio, uint8_t sm, uint8_t offset, uint8_t bit_depth, uint8_t dout_pin, uint8_t clock_pin_base) {
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pio_gpio_init(pio, dout_pin);
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pio_gpio_init(pio, clock_pin_base);
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pio_gpio_init(pio, clock_pin_base + 1);
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pio_sm_config sm_config = i2s_out_master_program_get_default_config(offset);
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sm_config_set_out_pins(&sm_config, dout_pin, 1);
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sm_config_set_sideset_pins(&sm_config, clock_pin_base);
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sm_config_set_out_shift(&sm_config, false, false, bit_depth);
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sm_config_set_fifo_join(&sm_config, PIO_FIFO_JOIN_TX);
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pio_sm_init(pio, sm, offset, &sm_config);
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uint32_t pin_mask = (1u << dout_pin) | (3u << clock_pin_base);
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pio_sm_set_pins_with_mask(pio, sm, 0, pin_mask); // zero output
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pio_sm_set_pindirs_with_mask(pio, sm, pin_mask, pin_mask);
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}
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%} |