Experiment with FM radio reception

grc/PicoSDR-WBFM.grc

@@ -0,0 +1,763 @@
+options:
+  parameters:
+    author: ''
+    catch_exceptions: 'True'
+    category: '[GRC Hier Blocks]'
+    cmake_opt: ''
+    comment: ''
+    copyright: ''
+    description: ''
+    gen_cmake: 'On'
+    gen_linking: dynamic
+    generate_options: qt_gui
+    hier_block_src_path: '.:'
+    id: PicoSDR
+    max_nouts: '0'
+    output_language: python
+    placement: (0,0)
+    qt_qss_theme: ''
+    realtime_scheduling: ''
+    run: 'True'
+    run_command: '{python} -u {filename}'
+    run_options: prompt
+    sizing_mode: fixed
+    thread_safe_setters: ''
+    title: Pico SDR
+    window_size: (1000,1000)
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [8, 8]
+    rotation: 0
+    state: enabled
+
+blocks:
+- name: bpsk
+  id: variable_constellation
+  parameters:
+    comment: ''
+    const_points: '[-1-1j, -1+1j, 1+1j, 1-1j]'
+    dims: '1'
+    normalization: digital.constellation.AMPLITUDE_NORMALIZATION
+    precision: '8'
+    rot_sym: '4'
+    soft_dec_lut: None
+    sym_map: '[0, 1, 3, 2]'
+    type: bpsk
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [280, 8.0]
+    rotation: 0
+    state: true
+- name: samp_rate
+  id: variable
+  parameters:
+    comment: ''
+    value: 1_536_000 // (1 << 3)
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [176, 8.0]
+    rotation: 0
+    state: enabled
+- name: analog_quadrature_demod_cf_0
+  id: analog_quadrature_demod_cf
+  parameters:
+    affinity: ''
+    alias: ''
+    comment: ''
+    gain: samp_rate/(2 * math.pi * (samp_rate / 2))
+    maxoutbuf: '0'
+    minoutbuf: '0'
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [712, 480.0]
+    rotation: 0
+    state: true
+- name: analog_wfm_rcv_pll_0
+  id: analog_wfm_rcv_pll
+  parameters:
+    affinity: ''
+    alias: ''
+    audio_decimation: '4'
+    comment: ''
+    deemph_tau: 75e-6
+    maxoutbuf: '0'
+    minoutbuf: '0'
+    quad_rate: samp_rate
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [704, 552.0]
+    rotation: 0
+    state: true
+- name: audio_sink_0
+  id: audio_sink
+  parameters:
+    affinity: ''
+    alias: ''
+    comment: ''
+    device_name: ''
+    num_inputs: '2'
+    ok_to_block: 'True'
+    samp_rate: samp_rate // 4
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [1000, 560.0]
+    rotation: 0
+    state: true
+- name: blocks_add_xx_0
+  id: blocks_add_xx
+  parameters:
+    affinity: ''
+    alias: ''
+    comment: ''
+    maxoutbuf: '0'
+    minoutbuf: '0'
+    num_inputs: '2'
+    type: float
+    vlen: '1'
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [1000, 632.0]
+    rotation: 0
+    state: true
+- name: blocks_interleaved_char_to_complex_0
+  id: blocks_interleaved_char_to_complex
+  parameters:
+    affinity: ''
+    alias: ''
+    comment: ''
+    maxoutbuf: '0'
+    minoutbuf: '0'
+    scale_factor: '127'
+    vector_input: 'False'
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [224, 208.0]
+    rotation: 0
+    state: true
+- name: blocks_message_debug_0
+  id: blocks_message_debug
+  parameters:
+    affinity: ''
+    alias: ''
+    comment: ''
+    en_uvec: 'True'
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [1000, 32.0]
+    rotation: 0
+    state: true
+- name: blocks_probe_rate_0
+  id: blocks_probe_rate
+  parameters:
+    affinity: ''
+    alias: ''
+    alpha: '0.05'
+    comment: ''
+    maxoutbuf: '0'
+    minoutbuf: '0'
+    mintime: '2500'
+    type: complex
+    vlen: '1'
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [704, 16.0]
+    rotation: 0
+    state: true
+- name: digital_costas_loop_cc_0
+  id: digital_costas_loop_cc
+  parameters:
+    affinity: ''
+    alias: ''
+    comment: ''
+    maxoutbuf: '0'
+    minoutbuf: '0'
+    order: '2'
+    use_snr: 'False'
+    w: 2 * math.pi / 100
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [704, 296.0]
+    rotation: 0
+    state: true
+- name: import_0
+  id: import
+  parameters:
+    alias: ''
+    comment: ''
+    imports: import math
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [440, 8.0]
+    rotation: 0
+    state: true
+- name: network_tcp_source_0
+  id: network_tcp_source
+  parameters:
+    addr: 127.0.0.1
+    affinity: ''
+    alias: ''
+    comment: ''
+    maxoutbuf: '0'
+    minoutbuf: '0'
+    port: '1234'
+    server: 'True'
+    type: byte
+    vlen: '1'
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [48, 200.0]
+    rotation: 0
+    state: true
+- name: qtgui_const_sink_x_0
+  id: qtgui_const_sink_x
+  parameters:
+    affinity: ''
+    alias: ''
+    alpha1: '1.0'
+    alpha10: '1.0'
+    alpha2: '1.0'
+    alpha3: '1.0'
+    alpha4: '1.0'
+    alpha5: '1.0'
+    alpha6: '1.0'
+    alpha7: '1.0'
+    alpha8: '1.0'
+    alpha9: '1.0'
+    autoscale: 'False'
+    axislabels: 'True'
+    color1: '"blue"'
+    color10: '"red"'
+    color2: '"red"'
+    color3: '"red"'
+    color4: '"red"'
+    color5: '"red"'
+    color6: '"red"'
+    color7: '"red"'
+    color8: '"red"'
+    color9: '"red"'
+    comment: ''
+    grid: 'True'
+    gui_hint: (2, 1, 1, 1)
+    label1: ''
+    label10: ''
+    label2: ''
+    label3: ''
+    label4: ''
+    label5: ''
+    label6: ''
+    label7: ''
+    label8: ''
+    label9: ''
+    legend: 'False'
+    marker1: '0'
+    marker10: '0'
+    marker2: '0'
+    marker3: '0'
+    marker4: '0'
+    marker5: '0'
+    marker6: '0'
+    marker7: '0'
+    marker8: '0'
+    marker9: '0'
+    name: '""'
+    nconnections: '1'
+    size: int(samp_rate // 30)
+    style1: '0'
+    style10: '0'
+    style2: '0'
+    style3: '0'
+    style4: '0'
+    style5: '0'
+    style6: '0'
+    style7: '0'
+    style8: '0'
+    style9: '0'
+    tr_chan: '0'
+    tr_level: '0.0'
+    tr_mode: qtgui.TRIG_MODE_FREE
+    tr_slope: qtgui.TRIG_SLOPE_POS
+    tr_tag: '""'
+    type: complex
+    update_time: 1/30
+    width1: '1'
+    width10: '1'
+    width2: '1'
+    width3: '1'
+    width4: '1'
+    width5: '1'
+    width6: '1'
+    width7: '1'
+    width8: '1'
+    width9: '1'
+    xmax: '1'
+    xmin: '-1'
+    ymax: '1'
+    ymin: '-1'
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [1000, 280.0]
+    rotation: 0
+    state: true
+- name: qtgui_time_sink_x_0
+  id: qtgui_time_sink_x
+  parameters:
+    affinity: ''
+    alias: ''
+    alpha1: '1.0'
+    alpha10: '1.0'
+    alpha2: '1.0'
+    alpha3: '1.0'
+    alpha4: '1.0'
+    alpha5: '1.0'
+    alpha6: '1.0'
+    alpha7: '1.0'
+    alpha8: '1.0'
+    alpha9: '1.0'
+    autoscale: 'False'
+    axislabels: 'True'
+    color1: blue
+    color10: dark blue
+    color2: red
+    color3: green
+    color4: black
+    color5: cyan
+    color6: magenta
+    color7: yellow
+    color8: dark red
+    color9: dark green
+    comment: ''
+    ctrlpanel: 'False'
+    entags: 'False'
+    grid: 'True'
+    gui_hint: (1, 0, 1, 1)
+    label1: I
+    label10: Signal 10
+    label2: Q
+    label3: Signal 3
+    label4: Signal 4
+    label5: Signal 5
+    label6: Signal 6
+    label7: Signal 7
+    label8: Signal 8
+    label9: Signal 9
+    legend: 'False'
+    marker1: '-1'
+    marker10: '-1'
+    marker2: '-1'
+    marker3: '-1'
+    marker4: '-1'
+    marker5: '-1'
+    marker6: '-1'
+    marker7: '-1'
+    marker8: '-1'
+    marker9: '-1'
+    name: '"IQ"'
+    nconnections: '1'
+    size: int(samp_rate // 30)
+    srate: samp_rate
+    stemplot: 'False'
+    style1: '1'
+    style10: '1'
+    style2: '1'
+    style3: '1'
+    style4: '1'
+    style5: '1'
+    style6: '1'
+    style7: '1'
+    style8: '1'
+    style9: '1'
+    tr_chan: '0'
+    tr_delay: '0'
+    tr_level: '0.0'
+    tr_mode: qtgui.TRIG_MODE_FREE
+    tr_slope: qtgui.TRIG_SLOPE_POS
+    tr_tag: '""'
+    type: complex
+    update_time: 1/30
+    width1: '1'
+    width10: '1'
+    width2: '1'
+    width3: '1'
+    width4: '1'
+    width5: '1'
+    width6: '1'
+    width7: '1'
+    width8: '1'
+    width9: '1'
+    ylabel: Amplitude
+    ymax: '1'
+    ymin: '-1'
+    yunit: '""'
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [704, 192.0]
+    rotation: 0
+    state: true
+- name: qtgui_time_sink_x_0_0
+  id: qtgui_time_sink_x
+  parameters:
+    affinity: ''
+    alias: ''
+    alpha1: '1.0'
+    alpha10: '1.0'
+    alpha2: '1.0'
+    alpha3: '1.0'
+    alpha4: '1.0'
+    alpha5: '1.0'
+    alpha6: '1.0'
+    alpha7: '1.0'
+    alpha8: '1.0'
+    alpha9: '1.0'
+    autoscale: 'False'
+    axislabels: 'True'
+    color1: blue
+    color10: dark blue
+    color2: red
+    color3: green
+    color4: black
+    color5: cyan
+    color6: magenta
+    color7: yellow
+    color8: dark red
+    color9: dark green
+    comment: ''
+    ctrlpanel: 'False'
+    entags: 'False'
+    grid: 'True'
+    gui_hint: (1, 1, 1, 1)
+    label1: "\u0394f"
+    label10: Signal 10
+    label2: Signal 2
+    label3: Signal 3
+    label4: Signal 4
+    label5: Signal 5
+    label6: Signal 6
+    label7: Signal 7
+    label8: Signal 8
+    label9: Signal 9
+    legend: 'False'
+    marker1: '-1'
+    marker10: '-1'
+    marker2: '-1'
+    marker3: '-1'
+    marker4: '-1'
+    marker5: '-1'
+    marker6: '-1'
+    marker7: '-1'
+    marker8: '-1'
+    marker9: '-1'
+    name: '"FM Demodulation"'
+    nconnections: '1'
+    size: (samp_rate // 30)
+    srate: samp_rate // 2
+    stemplot: 'False'
+    style1: '1'
+    style10: '1'
+    style2: '1'
+    style3: '1'
+    style4: '1'
+    style5: '1'
+    style6: '1'
+    style7: '1'
+    style8: '1'
+    style9: '1'
+    tr_chan: '0'
+    tr_delay: '0'
+    tr_level: '0.0'
+    tr_mode: qtgui.TRIG_MODE_FREE
+    tr_slope: qtgui.TRIG_SLOPE_POS
+    tr_tag: '""'
+    type: float
+    update_time: 1/30
+    width1: '1'
+    width10: '1'
+    width2: '1'
+    width3: '1'
+    width4: '1'
+    width5: '1'
+    width6: '1'
+    width7: '1'
+    width8: '1'
+    width9: '1'
+    ylabel: Frequency Offset
+    ymax: '1'
+    ymin: '-1'
+    yunit: '""'
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [1000, 456.0]
+    rotation: 0
+    state: true
+- name: qtgui_time_sink_x_0_1
+  id: qtgui_time_sink_x
+  parameters:
+    affinity: ''
+    alias: ''
+    alpha1: '1.0'
+    alpha10: '1.0'
+    alpha2: '1.0'
+    alpha3: '1.0'
+    alpha4: '1.0'
+    alpha5: '1.0'
+    alpha6: '1.0'
+    alpha7: '1.0'
+    alpha8: '1.0'
+    alpha9: '1.0'
+    autoscale: 'False'
+    axislabels: 'True'
+    color1: blue
+    color10: dark blue
+    color2: red
+    color3: green
+    color4: black
+    color5: cyan
+    color6: magenta
+    color7: yellow
+    color8: dark red
+    color9: dark green
+    comment: ''
+    ctrlpanel: 'False'
+    entags: 'False'
+    grid: 'True'
+    gui_hint: (2, 0, 1, 1)
+    label1: I
+    label10: Signal 10
+    label2: Q
+    label3: Signal 3
+    label4: Signal 4
+    label5: Signal 5
+    label6: Signal 6
+    label7: Signal 7
+    label8: Signal 8
+    label9: Signal 9
+    legend: 'False'
+    marker1: '-1'
+    marker10: '-1'
+    marker2: '-1'
+    marker3: '-1'
+    marker4: '-1'
+    marker5: '-1'
+    marker6: '-1'
+    marker7: '-1'
+    marker8: '-1'
+    marker9: '-1'
+    name: '"IQ / Loop"'
+    nconnections: '1'
+    size: int(samp_rate // 30)
+    srate: samp_rate
+    stemplot: 'False'
+    style1: '1'
+    style10: '1'
+    style2: '1'
+    style3: '1'
+    style4: '1'
+    style5: '1'
+    style6: '1'
+    style7: '1'
+    style8: '1'
+    style9: '1'
+    tr_chan: '0'
+    tr_delay: '0'
+    tr_level: '0.0'
+    tr_mode: qtgui.TRIG_MODE_FREE
+    tr_slope: qtgui.TRIG_SLOPE_POS
+    tr_tag: '""'
+    type: complex
+    update_time: 1/30
+    width1: '1'
+    width10: '1'
+    width2: '1'
+    width3: '1'
+    width4: '1'
+    width5: '1'
+    width6: '1'
+    width7: '1'
+    width8: '1'
+    width9: '1'
+    ylabel: Amplitude
+    ymax: '1'
+    ymin: '-1'
+    yunit: '""'
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [1000, 352.0]
+    rotation: 0
+    state: true
+- name: qtgui_waterfall_sink_x_0_0
+  id: qtgui_waterfall_sink_x
+  parameters:
+    affinity: ''
+    alias: ''
+    alpha1: '1.0'
+    alpha10: '1.0'
+    alpha2: '1.0'
+    alpha3: '1.0'
+    alpha4: '1.0'
+    alpha5: '1.0'
+    alpha6: '1.0'
+    alpha7: '1.0'
+    alpha8: '1.0'
+    alpha9: '1.0'
+    axislabels: 'True'
+    bw: samp_rate
+    color1: '0'
+    color10: '0'
+    color2: '0'
+    color3: '0'
+    color4: '0'
+    color5: '0'
+    color6: '0'
+    color7: '0'
+    color8: '0'
+    color9: '0'
+    comment: ''
+    fc: '0'
+    fftsize: '1024'
+    freqhalf: 'True'
+    grid: 'True'
+    gui_hint: (0, 0, 1, 2)
+    int_max: '0'
+    int_min: '-90'
+    label1: ''
+    label10: ''
+    label2: ''
+    label3: ''
+    label4: ''
+    label5: ''
+    label6: ''
+    label7: ''
+    label8: ''
+    label9: ''
+    legend: 'True'
+    maxoutbuf: '0'
+    minoutbuf: '0'
+    name: '"RF"'
+    nconnections: '1'
+    showports: 'False'
+    type: complex
+    update_time: 1/30
+    wintype: window.WIN_BLACKMAN_hARRIS
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [704, 88.0]
+    rotation: 0
+    state: true
+- name: qtgui_waterfall_sink_x_0_0_0
+  id: qtgui_waterfall_sink_x
+  parameters:
+    affinity: ''
+    alias: ''
+    alpha1: '1.0'
+    alpha10: '1.0'
+    alpha2: '1.0'
+    alpha3: '1.0'
+    alpha4: '1.0'
+    alpha5: '1.0'
+    alpha6: '1.0'
+    alpha7: '1.0'
+    alpha8: '1.0'
+    alpha9: '1.0'
+    axislabels: 'True'
+    bw: samp_rate // 4
+    color1: '0'
+    color10: '0'
+    color2: '0'
+    color3: '0'
+    color4: '0'
+    color5: '0'
+    color6: '0'
+    color7: '0'
+    color8: '0'
+    color9: '0'
+    comment: ''
+    fc: '0'
+    fftsize: '1024'
+    freqhalf: 'True'
+    grid: 'True'
+    gui_hint: (3, 0, 1, 2)
+    int_max: '0'
+    int_min: '-90'
+    label1: ''
+    label10: ''
+    label2: ''
+    label3: ''
+    label4: ''
+    label5: ''
+    label6: ''
+    label7: ''
+    label8: ''
+    label9: ''
+    legend: 'True'
+    maxoutbuf: '0'
+    minoutbuf: '0'
+    name: '"Audio"'
+    nconnections: '1'
+    showports: 'False'
+    type: float
+    update_time: 1/30
+    wintype: window.WIN_BLACKMAN_hARRIS
+  states:
+    bus_sink: false
+    bus_source: false
+    bus_structure: null
+    coordinate: [1144, 616.0]
+    rotation: 0
+    state: true
+
+connections:
+- [analog_quadrature_demod_cf_0, '0', qtgui_time_sink_x_0_0, '0']
+- [analog_wfm_rcv_pll_0, '0', audio_sink_0, '0']
+- [analog_wfm_rcv_pll_0, '0', blocks_add_xx_0, '0']
+- [analog_wfm_rcv_pll_0, '1', audio_sink_0, '1']
+- [analog_wfm_rcv_pll_0, '1', blocks_add_xx_0, '1']
+- [blocks_add_xx_0, '0', qtgui_waterfall_sink_x_0_0_0, '0']
+- [blocks_interleaved_char_to_complex_0, '0', analog_quadrature_demod_cf_0, '0']
+- [blocks_interleaved_char_to_complex_0, '0', analog_wfm_rcv_pll_0, '0']
+- [blocks_interleaved_char_to_complex_0, '0', blocks_probe_rate_0, '0']
+- [blocks_interleaved_char_to_complex_0, '0', digital_costas_loop_cc_0, '0']
+- [blocks_interleaved_char_to_complex_0, '0', qtgui_time_sink_x_0, '0']
+- [blocks_interleaved_char_to_complex_0, '0', qtgui_waterfall_sink_x_0_0, '0']
+- [blocks_probe_rate_0, rate, blocks_message_debug_0, print]
+- [digital_costas_loop_cc_0, '0', qtgui_const_sink_x_0, '0']
+- [digital_costas_loop_cc_0, '0', qtgui_time_sink_x_0_1, '0']
+- [network_tcp_source_0, '0', blocks_interleaved_char_to_complex_0, '0']
+
+metadata:
+  file_format: 1
+  grc_version: 3.10.6.0

src/main.c

@@ -37,18 +37,33 @@
 #include <limits.h>
 #include <stdlib.h>
 
+/* FM Radio */
+#if 1
+#define CLK_SYS_HZ (266 * MHZ)
+#define BANDWIDTH 1536000
+#define DECIMATION_BITS 3
+#define LPF_ORDER 2
+#define AGC_DECAY_BITS 20
+#define BIAS_STRENGTH 0
+#endif
+
+/* Digital Data */
+#if 0
 #define CLK_SYS_HZ (250 * MHZ)
 #define BANDWIDTH 1280000
 #define DECIMATION_BITS 6
-#define IQ_BLOCK_LEN 64
 #define LPF_ORDER 3
 #define AGC_DECAY_BITS 16
+#define BIAS_STRENGTH 5
+#endif
 
+#define IQ_BLOCK_LEN 64
 #define RX_SLEEP_US (DECIMATION * BANDWIDTH / (1 * MHZ) / 4)
 #define DECIMATION (1 << DECIMATION_BITS)
 
 static_assert(RX_SLEEP_US > 0, "RX_SLEEP_US must be positive");
 static_assert(LPF_ORDER <= 3, "LPF_ORDER must be 0-3");
+static_assert(BIAS_STRENGTH >= 0 && BIAS_STRENGTH <= 9, "BIAS_STRENGTH must be 0-9");
 
 #define XOR_ADDR 0x1000
 #define LO_COS_ACCUMULATOR (&pio1->sm[2].pinctrl)
@@ -111,6 +126,29 @@ static void bias_init(int in_pin, int out_pin)
 	const uint16_t insn[] = {
 		pio_encode_mov_not(pio_pins, pio_pins) | pio_encode_sideset(1, 1),
 		pio_encode_mov_not(pio_pins, pio_pins) | pio_encode_sideset(1, 1),
+
+		pio_encode_nop() | pio_encode_sideset(1, 0) | pio_encode_delay(0), /* 1 */
+		pio_encode_nop() | pio_encode_sideset(1, 0) | pio_encode_delay(0), /* 2 */
+		pio_encode_nop() | pio_encode_sideset(1, 0) | pio_encode_delay(1), /* 4 */
+		pio_encode_nop() | pio_encode_sideset(1, 0) | pio_encode_delay(3), /* 8 */
+
+		pio_encode_nop() | pio_encode_sideset(1, 0) | pio_encode_delay(7),  /* 16 */
+		pio_encode_nop() | pio_encode_sideset(1, 0) | pio_encode_delay(15), /* 32 */
+		pio_encode_nop() | pio_encode_sideset(1, 0) | pio_encode_delay(15), /* 48 */
+		pio_encode_nop() | pio_encode_sideset(1, 0) | pio_encode_delay(15), /* 64 */
+
+		pio_encode_nop() | pio_encode_sideset(1, 0) | pio_encode_delay(15),
+		pio_encode_nop() | pio_encode_sideset(1, 0) | pio_encode_delay(15),
+		pio_encode_nop() | pio_encode_sideset(1, 0) | pio_encode_delay(15),
+		pio_encode_nop() | pio_encode_sideset(1, 0) | pio_encode_delay(15),
+
+		pio_encode_nop() | pio_encode_sideset(1, 0) | pio_encode_delay(15),
+		pio_encode_nop() | pio_encode_sideset(1, 0) | pio_encode_delay(15),
+		pio_encode_nop() | pio_encode_sideset(1, 0) | pio_encode_delay(15),
+		pio_encode_nop() | pio_encode_sideset(1, 0) | pio_encode_delay(15),
+
+		pio_encode_nop() | pio_encode_sideset(1, 0) | pio_encode_delay(15),
+		pio_encode_nop() | pio_encode_sideset(1, 0) | pio_encode_delay(15),
 		pio_encode_nop() | pio_encode_sideset(1, 0) | pio_encode_delay(15),
 		pio_encode_nop() | pio_encode_sideset(1, 0) | pio_encode_delay(15),
 	};
@@ -118,7 +156,7 @@ static void bias_init(int in_pin, int out_pin)
 	pio_program_t prog = {
 		.instructions = insn,
 		.length = sizeof(insn) / sizeof(*insn),
-		.origin = 16,
+		.origin = 10,
 	};
 
 	pio_sm_set_enabled(pio1, 0, false);
@@ -134,7 +172,10 @@ static void bias_init(int in_pin, int out_pin)
 	sm_config_set_in_pins(&pc, in_pin);
 	sm_config_set_out_pins(&pc, out_pin, 1);
 	sm_config_set_set_pins(&pc, out_pin, 1);
-	sm_config_set_wrap(&pc, prog.origin, prog.origin + prog.length - 1);
+
+	int nops[10] = { 20, 12, 8, 6, 5, 4, 3, 2, 1, 0 };
+	sm_config_set_wrap(&pc, prog.origin, prog.origin + 1 + nops[BIAS_STRENGTH]);
+
 	sm_config_set_clkdiv_int_frac(&pc, 1, 0);
 	pio_sm_init(pio1, 0, prog.origin, &pc);
 
@@ -156,7 +197,7 @@ static void watch_init(int in_pin)
 	pio_program_t prog = {
 		.instructions = insn,
 		.length = 1,
-		.origin = 31,
+		.origin = 6,
 	};
 
 	pio_sm_set_enabled(pio1, 1, false);
@@ -191,7 +232,7 @@ static void send_init(int out_pin)
 	pio_program_t prog = {
 		.instructions = insn,
 		.length = 1,
-		.origin = 30,
+		.origin = 5,
 	};
 
 	pio_sm_set_enabled(pio1, 1, false);