tx-miso.pio

; Sony MI-SPI state machine for sending data in the MISO direction
; (Emulating a flash to a real body)
; 2023/04 Andrew Villeneuve

; Pin mapping:
; IN 0 = CLK
; OUT 0 = DATA

; The MISO START pulse will have already been evaluated when the SM starts,
; so the first CLK pulse we see should be for a data bit

.program miso

.wrap_target
	wait 1 pin 0			;wait for rising edge of clock (IN pin 0)
	out pins, 1 			;assert the next (1) bit from the OSR onto the DATA pin
	wait 0 pin 0 			;wait for falling edge of clock (IN pin 0)
.wrap

% c-sdk {
static inline void miso_program_init(PIO pio, uint sm, uint offset, uint clkpin, uint datapin) {
    pio_sm_config c = miso_program_get_default_config(offset);

    // Map Clock to IN pin 0, Data to OUT pin 0
    sm_config_set_in_pins(&c, clkpin);
    sm_config_set_out_pins(&c, datapin, 1);

    // Deliberately not selecting the PIO function for the DATA pin yet

    // OSR Shift: LSB first, Autopull enabled, every 8 bits

    sm_config_set_out_shift(&c, true, true, 8);

    // Load our configuration, and jump to the start of the program
    pio_sm_init(pio, sm, offset, &c);

}
%}