39 lines
1.1 KiB
Plaintext
39 lines
1.1 KiB
Plaintext
;
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; Copyright (c) 2021 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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.program resistor_dac_5bit
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; Drive one of the 5-bit resistor DACs on the VGA reference board. (this isn't
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; a good way to do VGA -- just want a nice sawtooth for the ADC example!)
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out pins, 5
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% c-sdk {
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#include "hardware/clocks.h"
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static inline void resistor_dac_5bit_program_init(PIO pio, uint sm, uint offset,
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uint sample_rate_hz, uint pin_base) {
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pio_sm_set_pins_with_mask(pio, sm, 0, 0x1fu << pin_base);
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pio_sm_set_pindirs_with_mask(pio, sm, ~0u, 0x1fu << pin_base);
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for (int i = 0; i < 5; ++i)
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pio_gpio_init(pio, pin_base + i);
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pio_sm_config c = resistor_dac_5bit_program_get_default_config(offset);
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sm_config_set_out_pins(&c, pin_base, 5);
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// Shift to right, autopull threshold 5
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sm_config_set_out_shift(&c, true, true, 5);
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// Deeper FIFO as we're not doing any RX
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sm_config_set_fifo_join(&c, PIO_FIFO_JOIN_TX);
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float div = (float)clock_get_hz(clk_sys) / sample_rate_hz;
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sm_config_set_clkdiv(&c, div);
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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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