Add I2S input slave support (#3244)

Due to the way the PIO inputs work, slave input mode needs to have
its pins defined in a fixed order:  DIN, BCLK, LRCLK

For slave mode, specify ``setDATA`` . ``setBCLK`` and ``setLRCLK``
are ignored.

Author: earlephilhower

docs/i2s.rst

@@ -39,8 +39,11 @@ any input or output can happen.
 bool setSlave()
 ~~~~~~~~~~~~~~~
 Enables slave mode.  BCLK and LRCLK are inputs and used to control the
-timing of the DOUT output.  Only normal I2S output mode is supported in
-slave mode.
+timing of the DOUT output.  Only normal I2S output and input modes are
+supported in slave mode.
+
+In I2S input slave mode, the clock pins and swapClocks are ignored.  The pins
+must be consecutive starting with DIN, then BCLK, then LRCLK.
 
 bool setBCLK(pin_size_t pin)
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~

libraries/I2S/src/I2S.cpp

@@ -332,6 +332,10 @@ bool I2S::begin() {
         pgm = &pio_i2s_out_program;
         init = pio_i2s_out_program_init;
         break;
+    case _SLAVE + _INPUT:
+        pgm = &pio_i2s_in_slave_program;
+        init = pio_i2s_in_slave_program_init;
+        break;
     case _INPUT:
         pgm = &pio_i2s_in_program;
         init = pio_i2s_in_program_init;

libraries/I2S/src/pio_i2s.pio

@@ -182,6 +182,34 @@ right1:
     ; Loop back to beginning...
 
 
+.program pio_i2s_in_slave
+; The C code should update SHIFTCTRL to be 24 or 32 (for 16- and 32- bit mode)
+
+; IN 0 = DIN
+; IN 1 = BCLK
+; IN 2 = LRCLK
+
+waitfirstbit:
+    wait 0 pin 1
+    wait 1 pin 1
+    jmp pin waitfirstbit; LRCLK==1, so this is right channel...wait for left
+
+.wrap_target
+readleft:
+    wait 0 pin 1
+    wait 1 pin 1
+    in pins, 1  ; read din on rising edge
+    jmp pin readright
+    jmp readleft
+
+readright:
+    wait 0 pin 1
+    wait 1 pin 1
+    in pins, 1
+    jmp pin readright
+.wrap
+
+
 .program pio_i2s_inout
 .side_set 2   ; 0 = bclk, 1=wclk
 
@@ -399,6 +427,28 @@ static inline void pio_i2s_in_program_init I2S_INIT_PARAMS {
     pio_sm_exec(pio, sm, pio_encode_in(pio_pins, bits - 1)); // Shift in 1st R data modulo one bit, avoiding bit shift from #2037
 }
 
+static inline void pio_i2s_in_slave_program_init I2S_INIT_PARAMS {
+    I2S_INIT_PARAMS_VOID;
+    // Note that the CLOCK_BASE pin is ignored.  It's DIN, BCLK, LRCLK consecutive due to PIO limitations
+    pio_gpio_init(pio, data_in_pin);
+    pio_gpio_init(pio, data_in_pin + 1);
+    pio_gpio_init(pio, data_in_pin + 2);
+
+    pio_sm_config sm_config = pio_i2s_in_slave_program_get_default_config(offset);
+
+    sm_config_set_in_pins(&sm_config, data_in_pin);
+    sm_config_set_in_pin_count(&sm_config, 3);
+    sm_config_set_in_shift(&sm_config, false, true, (bits <= 16) ? 2 * bits : bits);
+    sm_config_set_fifo_join(&sm_config, PIO_FIFO_JOIN_RX);
+    sm_config_set_jmp_pin(&sm_config, data_in_pin + 2);
+
+    pio_sm_init(pio, sm, offset, &sm_config);
+
+    pio_sm_set_consecutive_pindirs(pio, sm, data_in_pin, 3, false);
+}
+
+
+
 static inline void pio_i2s_inout_program_init I2S_INIT_PARAMS {
     I2S_INIT_PARAMS_VOID;
     pio_gpio_init(pio, data_in_pin);

libraries/I2S/src/pio_i2s.pio.h

@@ -324,6 +324,49 @@ static inline pio_sm_config pio_i2s_in_program_get_default_config(uint offset) {
 }
 #endif
 
+// ---------------- //
+// pio_i2s_in_slave //
+// ---------------- //
+
+#define pio_i2s_in_slave_wrap_target 3
+#define pio_i2s_in_slave_wrap 11
+#define pio_i2s_in_slave_pio_version 0
+
+static const uint16_t pio_i2s_in_slave_program_instructions[] = {
+    0x2021, //  0: wait   0 pin, 1
+    0x20a1, //  1: wait   1 pin, 1
+    0x00c0, //  2: jmp    pin, 0
+    //     .wrap_target
+    0x2021, //  3: wait   0 pin, 1
+    0x20a1, //  4: wait   1 pin, 1
+    0x4001, //  5: in     pins, 1
+    0x00c8, //  6: jmp    pin, 8
+    0x0003, //  7: jmp    3
+    0x2021, //  8: wait   0 pin, 1
+    0x20a1, //  9: wait   1 pin, 1
+    0x4001, // 10: in     pins, 1
+    0x00c8, // 11: jmp    pin, 8
+    //     .wrap
+};
+
+#if !PICO_NO_HARDWARE
+static const struct pio_program pio_i2s_in_slave_program = {
+    .instructions = pio_i2s_in_slave_program_instructions,
+    .length = 12,
+    .origin = -1,
+    .pio_version = pio_i2s_in_slave_pio_version,
+#if PICO_PIO_VERSION > 0
+    .used_gpio_ranges = 0x0
+#endif
+};
+
+static inline pio_sm_config pio_i2s_in_slave_program_get_default_config(uint offset) {
+    pio_sm_config c = pio_get_default_sm_config();
+    sm_config_set_wrap(&c, offset + pio_i2s_in_slave_wrap_target, offset + pio_i2s_in_slave_wrap);
+    return c;
+}
+#endif
+
 // ------------- //
 // pio_i2s_inout //
 // ------------- //
@@ -511,6 +554,21 @@ static inline void pio_i2s_in_program_init I2S_INIT_PARAMS {
     pio_sm_exec(pio, sm, pio_encode_in(pio_pins, bits)); // Shift in 1st L data
     pio_sm_exec(pio, sm, pio_encode_in(pio_pins, bits - 1)); // Shift in 1st R data modulo one bit, avoiding bit shift from #2037
 }
+static inline void pio_i2s_in_slave_program_init I2S_INIT_PARAMS {
+    I2S_INIT_PARAMS_VOID;
+    // Note that the CLOCK_BASE pin is ignored.  It's DIN, BCLK, LRCLK consecutive due to PIO limitations
+    pio_gpio_init(pio, data_in_pin);
+    pio_gpio_init(pio, data_in_pin + 1);
+    pio_gpio_init(pio, data_in_pin + 2);
+    pio_sm_config sm_config = pio_i2s_in_slave_program_get_default_config(offset);
+    sm_config_set_in_pins(&sm_config, data_in_pin);
+    sm_config_set_in_pin_count(&sm_config, 3);
+    sm_config_set_in_shift(&sm_config, false, true, (bits <= 16) ? 2 * bits : bits);
+    sm_config_set_fifo_join(&sm_config, PIO_FIFO_JOIN_RX);
+    sm_config_set_jmp_pin(&sm_config, data_in_pin + 2);
+    pio_sm_init(pio, sm, offset, &sm_config);
+    pio_sm_set_consecutive_pindirs(pio, sm, data_in_pin, 3, false);
+}
 static inline void pio_i2s_inout_program_init I2S_INIT_PARAMS {
     I2S_INIT_PARAMS_VOID;
     pio_gpio_init(pio, data_in_pin);