tmds_encode_1bpp.pio

.program tmds_encode_1bpp

; 1bpp black/white pixels go in, TMDS symbols come out.
; Each output word contains two output symbols, each 10 bits in size,
; right-justified. The least-significant symbol is displayed first.
;
; We can encode using the following LUT: (yes this is compliant)
;
; x % 2 | colour | symbol
; ------+--------+-------
; 0     | 0      | 0x100
; 0     | 1      | 0x200
; 1     | 0      | 0x1ff
; 1     | 1      | 0x2ff
;
; OSR: shift to right, autopull, threshold 32
; ISR: shift to right, autopush, threshold 24
;
; Note the ISR needs to be shifted to *right* so that we can get the first
; pixel in the less-significant position. Threshold 24 so we can get 8x 0-bits
; at the LSBs for free :)

even_pixel:
    out x, 1
    mov y, ~x
    in y, 1
    in x, 1

odd_pixel:
    mov x, ~null
    in x, 8
    out x, 1
    mov y, ~x
    in y, 1
    in x, 13     ; Bring total shift to 24, triggering push.

% c-sdk {
static inline void tmds_encode_1bpp_init(PIO pio, uint sm) {
    uint offset = pio_add_program(pio, &tmds_encode_1bpp_program);
    pio_sm_config c = tmds_encode_1bpp_program_get_default_config(offset);
    sm_config_set_out_shift(&c, true, true, 32);
    sm_config_set_in_shift(&c, true, true, 24);
    pio_sm_init(pio, sm, offset, &c);
    pio_sm_set_enabled(pio, sm, true);
}
%}