dac_dma: Support DAC_DMA on esp32s2

docs/en/api-reference/peripherals/dac.rst

@@ -19,7 +19,7 @@ The DAC driver allows these channels to be set to arbitrary voltages.
 
 .. only:: esp32s2
 
-    The DAC channels can also be driven with DMA-style written sample data by the digital controller, however the driver does not supported this yet.
+    The DAC channels can also be driven with DMA-style written sample data by the digital controller, please check the Application Example(DMA part) to get more information.
 
 
 For other analog output options, see the :doc:`Sigma-delta Modulation module <sdm>` and the :doc:`LED Control module <ledc>`. Both these modules produce high frequency PDM/PWM output, which can be hardware low-pass filtered in order to generate a lower frequency analog output.
@@ -40,6 +40,35 @@ Setting DAC channel 1 ({IDF_TARGET_DAC_CH_1}) voltage to approx 0.78 of VDD_A vo
     dac_output_voltage(DAC_CHANNEL_1, 200);
 
 
+.. only:: esp32s2
+
+For {IDF_TARGET_NAME}, DAC support to use DMA to send digital data to convert. Here is the example:
+
+.. code-block:: c
+
+    #include <driver/dac.h>
+
+    const dac_digi_config_t cfg = {
+        .mode = mode,
+        .interval = 100,
+        .dig_clk.use_apll = false,  // APB clk
+        .dig_clk.div_num = 79,      // See comments `adc_digi_clk_t`
+        .dig_clk.div_b = 1,
+        .dig_clk.div_a = 0,
+        .dac_dma_cnt = 1,           // The dac dma link number for your project
+        .dac_dma_length = 512,      // The dac dam link length for your project. Should fit the buffer you prepared with dac_dma_cnt.
+        .dac_dma_link_type = DAC_DMA_LINK_RECURSIVE,  //The link type.
+    };
+
+    dac_digi_initialize(&cfg);
+    dac_output_enable(DAC_CHANNEL_X);
+    dac_digi_start();
+    dac_digi_write_bytes((uint8_t*)buffer_you_prepared);
+    dac_digi_stop();
+    dac_digi_deinitialize();
+
+    
+
 API Reference
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