feature(i2s): add i2s driver

examples/peripherals/i2s/Makefile

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+#
+# This is a project Makefile. It is assumed the directory this Makefile resides in is a
+# project subdirectory.
+#
+
+PROJECT_NAME := i2s
+
+include $(IDF_PATH)/make/project.mk
+

examples/peripherals/i2s/README.md

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+# I2S Example
+
+(See the README.md file in the upper level 'examples' directory for more information about examples.)
+
+In this example, we generate a 100Hz triangle and sine wave and send it out from left and right channels at a sample rate of 36kHz through the I2S bus.
+
+## How to Use Example
+
+### Hardware Required
+
+* A development board with ESP8266 SoC (e.g., ESP8266-DevKitC, etc.)
+* A USB cable for power supply and programming
+
+### Configure the Project
+
+```
+make menuconfig
+```
+
+* Set serial port under Serial Flasher Options.
+
+### Build and Flash
+
+Build the project and flash it to the board, then run monitor tool to view serial output:
+
+```
+make -j4 flash monitor
+```
+
+(To exit the serial monitor, type ``Ctrl-]``.)
+
+See the Getting Started Guide for full steps to configure and use ESP-IDF to build projects.
+
+## Example Output
+
+Running this example, you will see the Bits per Sample changes every 5 seconds after you have run this example. You can use `i2s_set_clk` to change the Bits per Sample and the Sample Rate. The output log can be seen below:
+
+```
+Test bits=24 free mem=78188, written data=2880
+I (5655) i2s: DMA Malloc info, datalen=blocksize=480, dma_buf_count=6
+
+Test bits=16 free mem=78188, written data=1440
+I (10735) i2s: DMA Malloc info, datalen=blocksize=240, dma_buf_count=6
+
+Test bits=24 free mem=78188, written data=2880
+I (15835) i2s: DMA Malloc info, datalen=blocksize=480, dma_buf_count=6
+
+Test bits=16 free mem=78188, written data=1440
+I (20915) i2s: DMA Malloc info, datalen=blocksize=240, dma_buf_count=6
+```
+
+If you have a logic analyzer, you can use a logic analyzer to grab online data. The following table describes the pins we use by default (Note that you can also use other pins for the same purpose).
+
+| pin name| function | gpio_num |
+|:---:|:---:|:---:|
+| MCLK|main clock | GPIO_NUM_4 |
+| WS  |word select| GPIO_NUM_2 |
+| SCK |continuous serial clock| GPIO_NUM_15 |
+| SD  |serial data| GPIO_NUM_3 |
+
+## Troubleshooting
+
+* Program upload failure
+
+    * Hardware connection is not correct: run `make monitor`, and reboot your board to see if there are any output logs.
+    * The baud rate for downloading is too high: lower your baud rate in the `menuconfig` menu, and try again.
+
+For any technical queries, please open an [issue](https://github.com/espressif/ESP8266_RTOS_SDK/issues) on GitHub. We will get back to you soon.

examples/peripherals/i2s/main/component.mk

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+#
+# Main Makefile. This is basically the same as a component makefile.
+#

examples/peripherals/i2s/main/i2s_example_main.c

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+/* I2S Example
+  This example code will output 100Hz sine wave and triangle wave to 2-channel of I2S driver
+  Every 5 seconds, it will change bits_per_sample [16, 24, 32] for i2s data
+  This example code is in the Public Domain (or CC0 licensed, at your option.)
+  Unless required by applicable law or agreed to in writing, this
+  software is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
+  CONDITIONS OF ANY KIND, either express or implied.
+*/
+
+#include <stdio.h>
+#include <math.h>
+#include "freertos/FreeRTOS.h"
+#include "freertos/task.h"
+#include "driver/i2s.h"
+#include "esp_system.h"
+#include "esp8266/pin_mux_register.h"
+
+#define SAMPLE_RATE     (36000)
+#define I2S_NUM         (0)
+#define WAVE_FREQ_HZ    (100)
+#define PI              (3.14159265)
+#define I2S_MCLK_EN     (1)
+#define I2S_BCK_EN      (1)
+#define I2S_WS_EN       (1)
+#define I2S_DO_EN       (1)
+#define I2S_DI_EN       (0)
+
+#define SAMPLE_PER_CYCLE (SAMPLE_RATE/WAVE_FREQ_HZ)
+
+static void setup_triangle_sine_waves(int bits)
+{
+    int *samples_data = malloc(((bits + 8) / 16) * SAMPLE_PER_CYCLE * 4);
+    unsigned int i, sample_val;
+    double sin_float, triangle_float, triangle_step = (double) pow(2, bits) / SAMPLE_PER_CYCLE;
+    size_t i2s_bytes_write = 0;
+
+    printf("\r\nTest bits=%d free mem=%d, written data=%d\n", bits, esp_get_free_heap_size(), ((bits + 8) / 16)*SAMPLE_PER_CYCLE * 4);
+
+    triangle_float = -(pow(2, bits) / 2 - 1);
+
+    for (i = 0; i < SAMPLE_PER_CYCLE; i++) {
+        sin_float = sin(i * PI / 180.0);
+
+        if (sin_float >= 0) {
+            triangle_float += triangle_step;
+        } else {
+            triangle_float -= triangle_step;
+        }
+
+        sin_float *= (pow(2, bits) / 2 - 1);
+
+        if (bits == 16) {
+            sample_val = 0;
+            sample_val += (short)triangle_float;
+            sample_val = sample_val << 16;
+            sample_val += (short) sin_float;
+            samples_data[i] = sample_val;
+        } else if (bits == 24) { //1-bytes unused
+            samples_data[i * 2] = ((int) triangle_float) << 8;
+            samples_data[i * 2 + 1] = ((int) sin_float) << 8;
+        } else {
+            samples_data[i * 2] = ((int) triangle_float);
+            samples_data[i * 2 + 1] = ((int) sin_float);
+        }
+    }
+
+    i2s_set_clk(I2S_NUM, SAMPLE_RATE, bits, 2);
+    i2s_write(I2S_NUM, samples_data, ((bits + 8) / 16)*SAMPLE_PER_CYCLE * 4, &i2s_bytes_write, 100);
+
+    free(samples_data);
+}
+
+void app_main()
+{
+    // for 36Khz sample rates, we create 100Hz sine wave, every cycle need 36000/100 = 360 samples (4-bytes or 8-bytes each sample)
+    // depend on bits_per_sample
+    // using 6 buffers, we need 60-samples per buffer
+    // if 2-channels, 16-bit each channel, total buffer is 360*4 = 1440 bytes
+    // if 2-channels, 24-bit each channel, total buffer is 360*8 = 2880 bytes
+    i2s_config_t i2s_config = {
+        .mode = I2S_MODE_MASTER | I2S_MODE_TX,                                  // Only TX
+        .sample_rate = SAMPLE_RATE,
+        .bits_per_sample = 16,
+        .channel_format = I2S_CHANNEL_FMT_RIGHT_LEFT,                           // 2-channels
+        .communication_format = I2S_COMM_FORMAT_I2S | I2S_COMM_FORMAT_I2S_MSB,
+        .dma_buf_count = 6,
+        .dma_buf_len = 60
+    };
+    i2s_pin_config_t pin_config = {
+        .bck_o_en = I2S_BCK_EN,
+        .ws_o_en = I2S_WS_EN,
+        .data_out_en = I2S_DO_EN,
+        .data_in_en = I2S_DI_EN
+    };
+
+    i2s_driver_install(I2S_NUM, &i2s_config, 0, NULL);
+    i2s_set_pin(I2S_NUM, &pin_config);
+
+    if (I2S_MCLK_EN) {
+        PIN_FUNC_SELECT(PERIPHS_IO_MUX_GPIO4_U, FUNC_CLK_XTAL);
+    }
+
+    int test_bits = 16;
+
+    while (1) {
+        setup_triangle_sine_waves(test_bits);
+        vTaskDelay(5000 / portTICK_RATE_MS);
+        test_bits += 8;
+
+        if (test_bits > 24) {
+            test_bits = 16;
+        }
+    }
+}