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https://github.com/steve-m/hsdaoh-rp2350.git
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0a948ce64c
This avoids picking up the audio clock with the RF ADC as spurs in the spectrum, and requires a different PCM1802 mode config than before for 512fs oversampling: MODE0 = 1 MODE1 = 0 The resulting audio samplerate is 78125 Hz.
83 lines
2.3 KiB
Text
83 lines
2.3 KiB
Text
;
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; Copyright (c) 2024-2025 Steve Markgraf <steve@steve-m.de>
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;
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; SPDX-License-Identifier: BSD-3-Clause
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;
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; Sample 12 bit parallel ADC (AD9226) every 4 PIO cycles on rising clock edge,
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; pack four 12 bit samples in three 16 bit words
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; ADC clock output as side-set
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;
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; Data being pushed to the FIFO, four 12 bit samples A-D
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; First word: A03 A02 A01 A00 B11 B10 B09 B08 B07 B06 B05 B04 B03 B02 B01 B00
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; Second word: A07 A06 A05 A04 C11 C10 C09 C08 C07 C06 C05 C04 C03 C02 C01 C00
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; Third word: A11 A10 A09 A08 D11 D10 D09 D08 D07 D06 D05 D04 D03 D02 D01 D00
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.pio_version 1
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.program adc_12bit_input
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.side_set 2
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public entry_point:
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.wrap_target
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mov osr, pins side 3 ; sample A
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out isr, 4 side 0
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in pins, 12 side 3 ; sample B, autopush
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out isr, 4 side 0
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in pins, 12 side 3 ; sample C, autopush
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out isr, 4 side 0
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in pins, 12 side 3 ; sample D, autopush
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nop side 0
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.wrap
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% c-sdk {
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static inline void adc_12bit_input_program_init(PIO pio, uint sm, uint offset, uint pin, uint clk_pin)
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{
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pio_sm_config c = adc_12bit_input_program_get_default_config(offset);
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// Set the IN base pin to the provided `pin` parameter.
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sm_config_set_in_pins(&c, pin);
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// configure CLK pin for side-set
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sm_config_set_sideset_pins(&c, clk_pin);
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sm_config_set_sideset(&c, 2, false, false);
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pio_sm_set_consecutive_pindirs(pio, sm, clk_pin, 2, true);
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pio_gpio_init(pio, clk_pin);
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pio_gpio_init(pio, clk_pin+1);
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// Set the pin directions to input at the PIO
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// Set D0-D11 of the ADC as input
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pio_sm_set_consecutive_pindirs(pio, sm, pin, 12, false);
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// Connect these GPIOs to this PIO block
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for (int i = pin; i < (pin+12); i++)
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pio_gpio_init(pio, i);
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sm_config_set_in_shift(
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&c,
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false, // Shift-to-right = false (i.e. shift to left)
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true, // Autopush enabled
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16 // Autopush threshold = 16
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);
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// required in order to set shift-to-right to true (for the out, null ops)
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sm_config_set_out_shift(
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&c,
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true, // Shift-to-right = true
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false, // Autopush disabled
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1 // Autopush threshold: ignored
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);
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// We only receive, so disable the TX FIFO to make the RX FIFO deeper.
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sm_config_set_fifo_join(&c, PIO_FIFO_JOIN_RX);
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sm_config_set_clkdiv(&c, 2.f);
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// Load our configuration, and start the program from the beginning
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pio_sm_init(pio, sm, offset, &c);
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// pio_sm_set_enabled(pio, sm, true);
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}
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%}
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