audio_pwm.pio

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

.program pwm_one_bit_dither
.side_set 1 opt
; Format:
; | high len | low len | (dither) * n |
; OSR level
; cycle length = 7 + 2 + 127

; 136 clocks/cycle frequency 352941 / 16 = 22058
delay:
  nop [2]
.wrap_target
  out pins, 1
loops:
  mov x, isr        side 1
loop1:
  jmp x-- loop1
  mov x, y          side 0
loop0:
  jmp x-- loop0
  jmp !osre delay
public entry_point:
  pull
  out isr, 7
  out y, 7
.wrap

.program pwm_two_bit_dither
.side_set 1 opt
; Format:
; | high len | low len | (dither) * n |
; OSR level

; this 138 clocks/cycle frequency 347826 / 16 = 21739Hz
delay:
  nop [2]
.wrap_target
  out pins, 1
  out pins, 1
  out pins, 1
loops:
  mov x, isr        side 1
loop1:
  jmp x-- loop1
  mov x, y          side 0
loop0:
  jmp x-- loop0
  jmp !osre delay
entry_point:
  pull
  out isr, 7
  out y, 7
.wrap