; vim: set et:

.program dap_swd
.side_set 1 opt

; Pin assignments:
; - SWCLK is side-set pin 0
; - SWDIO is OUT pin 0 and IN pin 0
;
; Autopush and autopull must be enabled, and the serial frame size is set by
; configuring the push/pull threshold (32 bits). Shift should be left
;
; data is captured on the leading edge of each SWCLK pulse, and
; transitions on the trailing edge, or some time before the first leading edge.

start_thing:
    pull
    out y,  1
    out x, 31         side 0
    jmp !y start_swdo side 0

start_swdi:
loop_swdi:
    in pins, 1        side 1
    jmp x-- loop_swdi side 0
end_swdi:
    push              side 0
    jmp start_thing   side 0

start_swdo:
loop_swdo:
    out pins, 1       side 0
    jmp x-- loop_swdo side 1
end_swdo:
    jmp start_thing   side 0

% c-sdk {
static inline void dap_swd_program_init(PIO pio, uint sm, uint offset,
        uint16_t freq, uint pin_swclk, uint pin_swdio) {
    pio_sm_config c = dap_swd_program_get_default_config(offset);
    sm_config_set_out_pins(&c, pin_swdio, 1);
    sm_config_set_in_pins(&c, pin_swdio);
    sm_config_set_sideset_pins(&c, pin_swclk);
    // (shift to left, autopush/pull, threshold=nbits)
    sm_config_set_out_shift(&c, false, true, 8); // shift left feature is broken???
    sm_config_set_in_shift(&c, false, true, 8);
    sm_config_set_clkdiv(&c, (float)clock_get_hz(clk_sys) / (2 * freq));

    // SWCLK is high, SWDIO is input (pull hi)
    pio_sm_set_pins_with_mask(pio, sm,
            (1u << pin_swclk),
            (1u << pin_swclk) | (1u << pin_swdio));
    pio_sm_set_pindirs_with_mask(pio, sm,
            (1u << pin_swclk) | (0u << pin_swdio),
            (1u << pin_swclk) | (1u << pin_swdio));
    pio_gpio_init(pio, pin_swclk);
    pio_gpio_init(pio, pin_swdio);

    // swd is synchronous, so bypass input synchroniser to reduce input delay.
    hw_set_bits(&pio->input_sync_bypass, 1u << pin_swdio);
    gpio_set_pulls(pin_swclk, false, true); // SWDIO is pulled up
    pio_sm_init(pio, sm, offset, &c);
    pio_sm_set_enabled(pio, sm, true);
}

%}