hello.pio

;
; Copyright (c) 2020 Raspberry Pi (Trading) Ltd.
;
; SPDX-License-Identifier: BSD-3-Clause
;

.program NTSC_Sync  

    ; .5uS clock cycle 
.wrap_target
    set x, 28       ; 
    set y, 8
Line:       
    set pins, 0 [8] ;9 low 5uS = 10 cycles ; TV looked fine with 8 delay, car monitor looks better with 9
high:
    set pins, 1 [31] ; high for around 58.5uS = 117 cycles
    nop [31]
    nop [31]
    nop [20] ; 19
    jmp x--, Line               
    set pins, 0 [5] ;6
    jmp !y last    
    set x, 28       ; so no time is added to the signal when registers are reloaded 
    jmp y--, high
last:
    set pins, 0 [1]  ; 
    set pins, 1 [31] ;          ; so in the 29 x 9 loop above we get 261 lines, then the last line takes place and then vsync
    nop [31]
    nop [31]
    nop [20] ; 19
    set pins, 0 
    set x, 31 [31]
syncV:         ; The small inaccurate sync timings( Hsync being 4.5 instead of 4.7 ) and the fact that this is fake progressive scanning is probally whats causing vertical distortion, a remedy for this at the moment is fine tuning vertical sync. 
    jmp x--, syncV [3] ; synchronization pulses for switching between odd/even NTSC field will be added in future
    ;set x, 31 
    ;jmp y--, syncV
.wrap      
                    
.program pixels 

;.wrap_target 
end:    ;48 ns  
    ;set pins, 0
    wait 0 PIN, 0 ; 
    wait 1 PIN, 0  ;   backporch delays ( if the delay wasn't long enough the frame would have a left offset )
    nop [31]
    nop [31] 
    set y, 31 [2]; ; osr loop runs for 4 pixels/16 istructions * 32 x loops * 2 y loops = 256 pixels/2048 bits
    set x, 3 [31]
    pull [31]      ; backporch alignment
    nop [10]    ; 31
    ;nop [31]    ; since the timing of each pixel had to get cut down then the resolution shrunk and these extra delays are for moving it to middle of screen
    ;nop [31]
    ;nop [31]
push_video: ; 52.6uS  ; :::: DMA transfers get proven correct when there is no wandering blanking line ( line counting distortion )
   out pins, 8 [1]               
   jmp x--, push_video
   jmp !y, push_again
   pull 
   set x, 3 
   jmp y--, push_video    ; cutting horizontal res down in half to 128 pixels = 1024 bits = 32 DMA transfers 
push_again:
    set y, 31 
    set x, 3 ; first 4 then 3 on loop
    pull 
rerun: 
   out pins, 8 [1]            ; OUT pins go low by having the last 4 pixels be blank, OUT pins have to be low for Hsync
   jmp x--, rerun
   jmp !y, end
   pull
   set x, 3 
   jmp y--, rerun  

;8 bit output 256 times in 52.6uS
;8x256 = 2048
;2048 / 32 = 64 so there needs to be 64 pulls from OSR/DMA

% c-sdk {
static inline void NTSC_Sync_program_init(PIO pio, uint sm, uint offset, uint pin) {
    pio_sm_config c = NTSC_Sync_program_get_default_config(offset);

    // Map the state machine's OUT pin group to one pin, namely the `pin`
    // parameter to this function.
    //sm_config_set_out_pins(&c, pin, 1);
    sm_config_set_set_pins(&c, pin, 1);
    // Set this pin's GPIO function (connect PIO to the pad)
    pio_gpio_init(pio, pin);
    // Set the pin direction to output at the PIO
    pio_sm_set_consecutive_pindirs(pio, sm, pin, 1, true);
    sm_config_set_clkdiv(&c, 62.5f);

    // Load our configuration, and jump to the start of the program
    pio_sm_init(pio, sm, offset, &c);
    // Set the state machine running
    pio_sm_set_enabled(pio, sm, true);
}

static inline void pixels_program_init(PIO pio, uint sm, uint offset, uint pins, uint pin_num, uint PIN) {
    pio_sm_config c = pixels_program_get_default_config(offset);

    
    
    ;sm_config_set_out_shift(&c, true, false, 8); 
    sm_config_set_out_pins(&c, pins, 8);
    ;sm_config_set_set_pins(&c, pins, 5);
    sm_config_set_in_pins(&c, PIN);



    // Set this pin's GPIO function (connect PIO to the pad)
    pio_gpio_init(pio, PIN);
    pio_gpio_init(pio, 2);
    pio_gpio_init(pio, 3);
    pio_gpio_init(pio, 4);
    pio_gpio_init(pio, 5);
    pio_gpio_init(pio, 6);
    pio_gpio_init(pio, 7);
    pio_gpio_init(pio, 8);
    pio_gpio_init(pio, 9);
    

    // Set the pin direction to output at the PIO
    pio_sm_set_consecutive_pindirs(pio, sm, PIN, 1, false); // in
    pio_sm_set_consecutive_pindirs(pio, sm, pins, pin_num, true);



    sm_config_set_clkdiv(&c, 6); // 125MHz / 6 = 20.8MHz = 48nS cycles
    
    //sm_config_set_fifo_join(&c, PIO_FIFO_JOIN_TX);

    // Load our configuration, and jump to the start of the program
    pio_sm_init(pio, sm, offset, &c);
    // Set the state machine running
    pio_sm_set_enabled(pio, sm, true);
}
%}