mimxrt10xx: implement i2sout

tested on metro m7 (green prototype version) with max98357a i2s amplifier and the following test code:
```py
import board
import time
import digitalio
from audiobusio import I2SOut
from audiocore import RawSample
from microcontroller import pin
from ulab import numpy as np

n = np.array(np.sin(np.linspace(0, np.pi*2, 218, endpoint=False)) * 200, dtype=np.int16)
print(n)
r = RawSample(n, sample_rate=8000, channel_count=2)
def main():
    with digitalio.DigitalInOut(board.LED) as l:
        l.switch_to_output(True)
        value = False
        while True:
            with I2SOut(pin.GPIO_06, pin.GPIO_07, pin.GPIO_04) as i:
                time.sleep(.01)
                l.value = value = not value
                i.play(r, loop=True)
                print(i.playing)
                time.sleep(.5)
                i.stop()
                print("STOPPED")
                print(i.playing)
                time.sleep(.5)
                i.play(r, loop=True)
                print(i.playing)
                print("PLAY AGAIN")
                time.sleep(.5)
            time.sleep(1)
```

Only stereo, 16-bit, raw samples were tested; the sample rate is actually fixed
at 48kHz in the core right now. There is more to do, but the basics work.

# Conflicts:
#	ports/mimxrt10xx/Makefile
#	ports/mimxrt10xx/mpconfigport.mk

Author: jepler

ports/mimxrt10xx/Makefile

@@ -119,6 +119,7 @@ SRC_SDK := \
 	drivers/lpuart/fsl_lpuart.c \
 	drivers/ocotp/fsl_ocotp.c \
 	drivers/pwm/fsl_pwm.c \
+	drivers/sai/fsl_sai.c \
 	drivers/snvs_hp/fsl_snvs_hp.c \
 	drivers/snvs_lp/fsl_snvs_lp.c \
 	drivers/tempmon/fsl_tempmon.c \
@@ -146,11 +147,6 @@ SRC_C += \
 
 endif
 
-# TODO
-#ifeq ($(CIRCUITPY_AUDIOBUSIO),1)
-#SRC_C += peripherals/samd/i2s.c peripherals/samd/$(CHIP_FAMILY)/i2s.c
-#endif
-#
 SRC_COMMON_HAL_EXPANDED = $(addprefix shared-bindings/, $(SRC_COMMON_HAL)) \
                           $(addprefix shared-bindings/, $(SRC_BINDINGS_ENUMS)) \
                           $(addprefix common-hal/, $(SRC_COMMON_HAL))

ports/mimxrt10xx/background.c

@@ -35,9 +35,6 @@ void PLACE_IN_ITCM(port_background_task)(void) {
 }
 
 void port_background_tick(void) {
-    #if CIRCUITPY_AUDIOIO || CIRCUITPY_AUDIOBUSIO
-    audio_dma_background();
-    #endif
 }
 
 void port_start_background_task(void) {

ports/mimxrt10xx/boards/metro_m7_1011/pins.c

@@ -56,5 +56,9 @@ STATIC const mp_rom_map_elem_t board_module_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR_STEMMA_I2C), MP_ROM_PTR(&board_i2c_obj) },
     { MP_ROM_QSTR(MP_QSTR_SPI), MP_ROM_PTR(&board_spi_obj) },
     { MP_ROM_QSTR(MP_QSTR_UART), MP_ROM_PTR(&board_uart_obj) },
+
+    { MP_ROM_QSTR(MP_QSTR_I2S_WSEL), MP_ROM_PTR(&pin_GPIO_06) }, // D10
+    { MP_ROM_QSTR(MP_QSTR_I2S_BCLK), MP_ROM_PTR(&pin_GPIO_07) }, // D9
+    { MP_ROM_QSTR(MP_QSTR_I2S_DOUT), MP_ROM_PTR(&pin_GPIO_04) }, // D12
 };
 MP_DEFINE_CONST_DICT(board_module_globals, board_module_globals_table);

ports/mimxrt10xx/common-hal/audiobusio/I2SOut.c

@@ -0,0 +1,154 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2020 Jeff Epler for Adafruit Industries
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include <stdint.h>
+#include <string.h>
+
+#include "mpconfigport.h"
+
+// Some boards don't implement I2SOut, so suppress any routines from here.
+#if CIRCUITPY_AUDIOBUSIO_I2SOUT
+
+#include "py/gc.h"
+#include "py/mperrno.h"
+#include "py/runtime.h"
+#include "common-hal/audiobusio/I2SOut.h"
+#include "shared-bindings/audiobusio/I2SOut.h"
+#include "shared-bindings/audiocore/RawSample.h"
+#include "shared-bindings/microcontroller/Pin.h"
+#include "supervisor/shared/translate/translate.h"
+#include "supervisor/shared/tick.h"
+
+// Where required we use identifier names that are required by NXP's
+// API, even though they do not conform to the naming standards that Adafruit
+// strives to adhere to. https://www.adafruit.com/blacklivesmatter
+#include "sdk/drivers/sai/fsl_sai.h"
+
+STATIC void config_periph_pin(const mcu_periph_obj_t *periph) {
+    if (!periph) {
+        return;
+    }
+    if (periph->pin->mux_reg) {
+        IOMUXC_SetPinMux(
+            periph->pin->mux_reg, periph->mux_mode,
+            periph->input_reg, periph->input_idx,
+            0,
+            1);
+    }
+
+    IOMUXC_SetPinConfig(0, 0, 0, 0,
+        periph->pin->cfg_reg,
+        IOMUXC_SW_PAD_CTL_PAD_HYS(0)
+        | IOMUXC_SW_PAD_CTL_PAD_PUS(0)
+        | IOMUXC_SW_PAD_CTL_PAD_PUE(0)
+        | IOMUXC_SW_PAD_CTL_PAD_PKE(1)
+        | IOMUXC_SW_PAD_CTL_PAD_ODE(0)
+        | IOMUXC_SW_PAD_CTL_PAD_SPEED(2)
+        | IOMUXC_SW_PAD_CTL_PAD_DSE(4)
+        | IOMUXC_SW_PAD_CTL_PAD_SRE(0));
+}
+
+// Caller validates that pins are free.
+void common_hal_audiobusio_i2sout_construct(audiobusio_i2sout_obj_t *self,
+    const mcu_pin_obj_t *bit_clock, const mcu_pin_obj_t *word_select,
+    const mcu_pin_obj_t *data, bool left_justified) {
+
+    int instance = -1;
+    const mcu_periph_obj_t *bclk_periph = find_pin_function(mcu_sai_tx_bclk_list, bit_clock, &instance, MP_QSTR_bit_clock);
+    const mcu_periph_obj_t *sync_periph = find_pin_function(mcu_sai_tx_sync_list, word_select, &instance, MP_QSTR_word_select);
+    const mcu_periph_obj_t *data_periph = find_pin_function(mcu_sai_tx_data0_list, data, &instance, MP_QSTR_data);
+
+    sai_transceiver_t config;
+    SAI_GetClassicI2SConfig(&config, 16, kSAI_Stereo, 1);
+    config.syncMode = kSAI_ModeAsync;
+    config.fifo.fifoPacking = kSAI_FifoPackingDisabled;
+    // These identifier names are required by NXP's API, even though they do
+    // not conform to the naming standards that Adafruit strives to adhere to.
+    // https://www.adafruit.com/blacklivesmatter
+    config.masterSlave = kSAI_Master;
+    port_i2s_initialize(&self->i2s, instance, &config);
+
+    self->bit_clock = bit_clock;
+    self->word_select = word_select;
+    self->data = data;
+    claim_pin(bit_clock);
+    claim_pin(word_select);
+    claim_pin(data);
+    config_periph_pin(data_periph);
+    config_periph_pin(sync_periph);
+    config_periph_pin(bclk_periph);
+}
+
+bool common_hal_audiobusio_i2sout_deinited(audiobusio_i2sout_obj_t *self) {
+    return port_i2s_deinited(&self->i2s);
+}
+
+void common_hal_audiobusio_i2sout_deinit(audiobusio_i2sout_obj_t *self) {
+    if (common_hal_audiobusio_i2sout_deinited(self)) {
+        return;
+    }
+
+    port_i2s_deinit(&self->i2s);
+
+    common_hal_reset_pin(self->bit_clock);
+    self->bit_clock = NULL;
+
+    common_hal_reset_pin(self->word_select);
+    self->word_select = NULL;
+
+    common_hal_reset_pin(self->data);
+    self->data = NULL;
+}
+
+void common_hal_audiobusio_i2sout_play(audiobusio_i2sout_obj_t *self,
+    mp_obj_t sample, bool loop) {
+    if (common_hal_audiobusio_i2sout_get_playing(self)) {
+        common_hal_audiobusio_i2sout_stop(self);
+    }
+    port_i2s_play(&self->i2s, sample, loop);
+}
+
+void common_hal_audiobusio_i2sout_pause(audiobusio_i2sout_obj_t *self) {
+    port_i2s_pause(&self->i2s);
+}
+
+void common_hal_audiobusio_i2sout_resume(audiobusio_i2sout_obj_t *self) {
+    port_i2s_resume(&self->i2s);
+}
+
+bool common_hal_audiobusio_i2sout_get_paused(audiobusio_i2sout_obj_t *self) {
+    return port_i2s_get_paused(&self->i2s);
+}
+
+void common_hal_audiobusio_i2sout_stop(audiobusio_i2sout_obj_t *self) {
+    port_i2s_stop(&self->i2s);
+}
+
+bool common_hal_audiobusio_i2sout_get_playing(audiobusio_i2sout_obj_t *self) {
+    return port_i2s_get_playing(&self->i2s);
+}
+
+#endif // CIRCUITPY_AUDIOBUSIO_I2SOUT

ports/mimxrt10xx/common-hal/audiobusio/I2SOut.h

@@ -0,0 +1,47 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2020 Jeff Epler for Adafruit Industries
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#pragma once
+
+#include "supervisor/background_callback.h"
+#include "common-hal/microcontroller/Pin.h"
+
+#include "common-hal/audiobusio/__init__.h"
+
+// Some boards don't implement I2SOut, so suppress any routines from here.
+#if CIRCUITPY_AUDIOBUSIO_I2SOUT
+
+#include "sdk/drivers/sai/fsl_sai.h"
+
+typedef struct {
+    mp_obj_base_t base;
+    i2s_t i2s;
+    const mcu_pin_obj_t *bit_clock;
+    const mcu_pin_obj_t *word_select;
+    const mcu_pin_obj_t *data;
+} audiobusio_i2sout_obj_t;
+
+#endif