stm: Add DMA support to Audio object.

stm/audio.c

 #include <stdint.h>
 #include <string.h>
 
-#include "stm32f4xx_rcc.h"
-#include "stm32f4xx_gpio.h"
 #include "stm32f4xx_dac.h"
 
 #include "nlr.h"
@@ -11,38 +9,34 @@
 #include "qstr.h"
 #include "parse.h"
 #include "obj.h"
+#include "map.h"
 #include "runtime.h"
 
 #include "audio.h"
 
-#define SAMPLE_BUF_SIZE (32)
+STATIC void TIM7_Config(uint freq) {
+    // TIM7 clock enable
+    RCC_APB1PeriphClockCmd(RCC_APB1Periph_TIM7, ENABLE);
 
-// sample_buf_in is always the same or ahead of sample_buf_out
-// when they are the same, there are no more samples left to process
-// in this scheme, there is always 1 unusable byte in the buffer, just before sample_buf_out
-int sample_buf_in;
-int sample_buf_out;
-byte sample_buf[SAMPLE_BUF_SIZE];
+    // reset TIM7
+    TIM_DeInit(TIM7);
 
-bool audio_is_full(void) {
-    return ((sample_buf_in + 1) % SAMPLE_BUF_SIZE) == sample_buf_out;
-}
+    // Compute the prescaler value so TIM7 triggers at freq-Hz
+    uint16_t period = (uint16_t) ((SystemCoreClock / 2) / freq) - 1;
 
-void audio_fill(byte sample) {
-    sample_buf[sample_buf_in] = sample;
-    sample_buf_in = (sample_buf_in + 1) % SAMPLE_BUF_SIZE;
-    // enable interrupt
-}
+    // Time base configuration
+    TIM_TimeBaseInitTypeDef TIM_TimeBaseStructure;
+    TIM_TimeBaseStructure.TIM_Period = period; // timer triggers with this period
+    TIM_TimeBaseStructure.TIM_Prescaler = 0; // timer runs at SystemCoreClock / 2
+    TIM_TimeBaseStructure.TIM_ClockDivision = 0; // unused for TIM7
+    TIM_TimeBaseStructure.TIM_CounterMode = TIM_CounterMode_Up; // unused for TIM7
+    TIM_TimeBaseInit(TIM7, &TIM_TimeBaseStructure);
 
-void audio_drain(void) {
-    if (sample_buf_in == sample_buf_out) {
-        // buffer is empty; disable interrupt
-    } else {
-        // buffer has a sample; output it
-        byte sample = sample_buf[sample_buf_out];
-        DAC_SetChannel2Data(DAC_Align_8b_R, sample);
-        sample_buf_out = (sample_buf_out + 1) % SAMPLE_BUF_SIZE;
-    }
+    // TIM7 TRGO selection
+    TIM_SelectOutputTrigger(TIM7, TIM_TRGOSource_Update);
+
+    // TIM7 enable counter
+    TIM_Cmd(TIM7, ENABLE);
 }
 
 /******************************************************************************/
@@ -50,13 +44,67 @@ void audio_drain(void) {
 
 typedef struct _pyb_audio_t {
     mp_obj_base_t base;
-    int dac_id; // 1 or 2
+    uint dac_channel; // DAC_Channel_1 or DAC_Channel_2
+    DMA_Stream_TypeDef *dma_stream; // DMA1_Stream6 or DMA1_Stream7
 } pyb_audio_t;
 
+mp_obj_t pyb_audio_noise(mp_obj_t self_in, mp_obj_t freq) {
+    pyb_audio_t *self = self_in;
+
+    // set TIM7 to trigger the DAC at the given frequency
+    TIM7_Config(mp_obj_get_int(freq));
+
+    DAC_Cmd(self->dac_channel, DISABLE);
+
+    DAC_InitTypeDef DAC_InitStructure;
+    DAC_InitStructure.DAC_Trigger = DAC_Trigger_T7_TRGO;
+    DAC_InitStructure.DAC_WaveGeneration = DAC_WaveGeneration_Noise;
+    DAC_InitStructure.DAC_LFSRUnmask_TriangleAmplitude = DAC_LFSRUnmask_Bits10_0;
+    DAC_InitStructure.DAC_OutputBuffer = DAC_OutputBuffer_Enable;
+    DAC_Init(self->dac_channel, &DAC_InitStructure);
+
+    DAC_Cmd(self->dac_channel, ENABLE);
+
+    if (self->dac_channel == DAC_Channel_1) {
+        DAC_SetChannel1Data(DAC_Align_12b_L, 0x7ff0);
+    } else {
+        DAC_SetChannel2Data(DAC_Align_12b_L, 0x7ff0);
+    }
+
+    return mp_const_none;
+}
+
+mp_obj_t pyb_audio_triangle(mp_obj_t self_in, mp_obj_t freq) {
+    pyb_audio_t *self = self_in;
+
+    // set TIM7 to trigger the DAC at the given frequency
+    TIM7_Config(mp_obj_get_int(freq));
+
+    DAC_Cmd(self->dac_channel, DISABLE);
+
+    DAC_InitTypeDef DAC_InitStructure;
+    DAC_InitStructure.DAC_Trigger = DAC_Trigger_T7_TRGO;
+    DAC_InitStructure.DAC_WaveGeneration = DAC_WaveGeneration_Triangle;
+    DAC_InitStructure.DAC_LFSRUnmask_TriangleAmplitude = DAC_TriangleAmplitude_1023;
+    DAC_InitStructure.DAC_OutputBuffer = DAC_OutputBuffer_Enable;
+    DAC_Init(self->dac_channel, &DAC_InitStructure);
+
+    DAC_Cmd(self->dac_channel, ENABLE);
+
+    // set base value of triangle wave
+    if (self->dac_channel == DAC_Channel_1) {
+        DAC_SetChannel1Data(DAC_Align_12b_R, 0x100);
+    } else {
+        DAC_SetChannel2Data(DAC_Align_12b_R, 0x100);
+    }
+
+    return mp_const_none;
+}
+
 // direct access to DAC
 mp_obj_t pyb_audio_dac(mp_obj_t self_in, mp_obj_t val) {
     pyb_audio_t *self = self_in;
-    if (self->dac_id == 1) {
+    if (self->dac_channel == DAC_Channel_1) {
         DAC_SetChannel1Data(DAC_Align_8b_R, mp_obj_get_int(val));
     } else {
         DAC_SetChannel2Data(DAC_Align_8b_R, mp_obj_get_int(val));
@@ -64,27 +112,92 @@ mp_obj_t pyb_audio_dac(mp_obj_t self_in, mp_obj_t val) {
     return mp_const_none;
 }
 
-mp_obj_t pyb_audio_is_full(mp_obj_t self_in) {
-    if (audio_is_full()) {
-        return mp_const_true;
+#define DAC_DHR8R1_ADDRESS (DAC_BASE + 0x10)
+#define DAC_DHR8R2_ADDRESS (DAC_BASE + 0x1c)
+
+// initiates a burst of RAM->DAC using DMA
+// input data is treated as an array of bytes (8 bit data)
+// TIM7 is used to set the frequency of the transfer
+mp_obj_t pyb_audio_dma(uint n_args, const mp_obj_t *args, mp_map_t *kw_args) {
+    pyb_audio_t *self = args[0];
+
+    // set TIM7 to trigger the DAC at the given frequency
+    TIM7_Config(mp_obj_get_int(args[2]));
+
+    mp_obj_type_t *type = mp_obj_get_type(args[1]);
+    if (type->buffer_p.get_buffer == NULL) {
+        nlr_jump(mp_obj_new_exception_msg(&mp_type_TypeError, "buffer argument must support buffer protocol"));
+    }
+    buffer_info_t bufinfo;
+    type->buffer_p.get_buffer(args[1], &bufinfo, BUFFER_READ);
+
+    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA1, ENABLE);
+
+    DMA_Cmd(self->dma_stream, DISABLE);
+    while (DMA_GetCmdStatus(self->dma_stream) != DISABLE) {
+    }
+
+    DAC_Cmd(self->dac_channel, DISABLE);
+
+    // DAC channel configuration
+    DAC_InitTypeDef DAC_InitStructure;
+    DAC_InitStructure.DAC_Trigger = DAC_Trigger_T7_TRGO;
+    DAC_InitStructure.DAC_WaveGeneration = DAC_WaveGeneration_None;
+    DAC_InitStructure.DAC_LFSRUnmask_TriangleAmplitude = DAC_TriangleAmplitude_1; // unused, but need to set it to a valid value
+    DAC_InitStructure.DAC_OutputBuffer = DAC_OutputBuffer_Enable;
+    DAC_Init(self->dac_channel, &DAC_InitStructure);
+
+    // DMA1_Stream[67] channel7 configuration
+    DMA_DeInit(self->dma_stream);
+    DMA_InitTypeDef DMA_InitStructure;
+    DMA_InitStructure.DMA_Channel = DMA_Channel_7;
+    if (self->dac_channel == DAC_Channel_1) {
+        DMA_InitStructure.DMA_PeripheralBaseAddr = DAC_DHR8R1_ADDRESS;
     } else {
-        return mp_const_false;
+        DMA_InitStructure.DMA_PeripheralBaseAddr = DAC_DHR8R2_ADDRESS;
     }
-}
+    DMA_InitStructure.DMA_Memory0BaseAddr = (uint32_t)bufinfo.buf;
+    DMA_InitStructure.DMA_DIR = DMA_DIR_MemoryToPeripheral;
+    DMA_InitStructure.DMA_BufferSize = bufinfo.len;
+    DMA_InitStructure.DMA_PeripheralInc = DMA_PeripheralInc_Disable;
+    DMA_InitStructure.DMA_MemoryInc = DMA_MemoryInc_Enable;
+    DMA_InitStructure.DMA_PeripheralDataSize = DMA_PeripheralDataSize_Byte;
+    DMA_InitStructure.DMA_MemoryDataSize = DMA_MemoryDataSize_Byte;
+    mp_map_elem_t *kw_mode = mp_map_lookup(kw_args, MP_OBJ_NEW_QSTR(qstr_from_str("mode")), MP_MAP_LOOKUP);
+    DMA_InitStructure.DMA_Mode = kw_mode == NULL ? DMA_Mode_Normal : mp_obj_get_int(kw_mode->value); // normal = 0, circular = 0x100
+    DMA_InitStructure.DMA_Priority = DMA_Priority_High;
+    DMA_InitStructure.DMA_FIFOMode = DMA_FIFOMode_Disable;
+    DMA_InitStructure.DMA_FIFOThreshold = DMA_FIFOThreshold_HalfFull;
+    DMA_InitStructure.DMA_MemoryBurst = DMA_MemoryBurst_Single;
+    DMA_InitStructure.DMA_PeripheralBurst = DMA_PeripheralBurst_Single;
+    DMA_Init(self->dma_stream, &DMA_InitStructure);
+
+    // enable DMA stream
+    DMA_Cmd(self->dma_stream, ENABLE);
+    while (DMA_GetCmdStatus(self->dma_stream) == DISABLE) {
+    }
+
+    // enable DAC channel
+    DAC_Cmd(self->dac_channel, ENABLE);
+
+    // enable DMA for DAC channel
+    DAC_DMACmd(self->dac_channel, ENABLE);
+
+    //printf("DMA: %p %lu\n", bufinfo.buf, bufinfo.len);
 
-mp_obj_t pyb_audio_fill(mp_obj_t self_in, mp_obj_t val) {
-    audio_fill(mp_obj_get_int(val));
     return mp_const_none;
 }
 
+STATIC MP_DEFINE_CONST_FUN_OBJ_2(pyb_audio_noise_obj, pyb_audio_noise);
+STATIC MP_DEFINE_CONST_FUN_OBJ_2(pyb_audio_triangle_obj, pyb_audio_triangle);
 STATIC MP_DEFINE_CONST_FUN_OBJ_2(pyb_audio_dac_obj, pyb_audio_dac);
-STATIC MP_DEFINE_CONST_FUN_OBJ_1(pyb_audio_is_full_obj, pyb_audio_is_full);
-STATIC MP_DEFINE_CONST_FUN_OBJ_2(pyb_audio_fill_obj, pyb_audio_fill);
+STATIC MP_DEFINE_CONST_FUN_OBJ_KW(pyb_audio_dma_obj, 3, pyb_audio_dma);
 
 STATIC const mp_method_t pyb_audio_methods[] = {
+    { "noise", &pyb_audio_noise_obj },
+    { "triangle", &pyb_audio_triangle_obj },
     { "dac", &pyb_audio_dac_obj },
-    { "is_full", &pyb_audio_is_full_obj },
-    { "fill", &pyb_audio_fill_obj },
+    { "dma", &pyb_audio_dma_obj },
     { NULL, NULL },
 };
 
@@ -94,8 +207,8 @@ STATIC const mp_obj_type_t pyb_audio_type = {
     .methods = pyb_audio_methods,
 };
 
-STATIC const pyb_audio_t pyb_audio_channel_1 = {{&pyb_audio_type}, 1};
-STATIC const pyb_audio_t pyb_audio_channel_2 = {{&pyb_audio_type}, 2};
+STATIC const pyb_audio_t pyb_audio_channel_1 = {{&pyb_audio_type}, DAC_Channel_1, DMA1_Stream5};
+STATIC const pyb_audio_t pyb_audio_channel_2 = {{&pyb_audio_type}, DAC_Channel_2, DMA1_Stream6};
 
 // create the audio object
 // currently support either DAC1 on X5 (id = 1) or DAC2 on X6 (id = 2)
@@ -106,17 +219,14 @@ STATIC mp_obj_t pyb_Audio(mp_obj_t id) {
 
     int dac_id = mp_obj_get_int(id);
     uint pin;
-    uint channel;
-    mp_obj_t dac_obj;
+    const pyb_audio_t *dac_obj;
 
     if (dac_id == 1) {
         pin = GPIO_Pin_4;
-        channel = DAC_Channel_1;
-        dac_obj = (mp_obj_t)&pyb_audio_channel_1;
+        dac_obj = &pyb_audio_channel_1;
     } else {
         pin = GPIO_Pin_5;
-        channel = DAC_Channel_2;
-        dac_obj = (mp_obj_t)&pyb_audio_channel_2;
+        dac_obj = &pyb_audio_channel_2;
     }
 
     // DAC channel configuration
@@ -130,19 +240,17 @@ STATIC mp_obj_t pyb_Audio(mp_obj_t id) {
     DAC_InitTypeDef DAC_InitStructure;
     DAC_InitStructure.DAC_Trigger = DAC_Trigger_None;
     DAC_InitStructure.DAC_WaveGeneration = DAC_WaveGeneration_None;
+    DAC_InitStructure.DAC_LFSRUnmask_TriangleAmplitude = DAC_TriangleAmplitude_1023;
     DAC_InitStructure.DAC_OutputBuffer = DAC_OutputBuffer_Enable;
-    DAC_Init(channel, &DAC_InitStructure);
+    DAC_Init(dac_obj->dac_channel, &DAC_InitStructure);
 
     // Enable DAC Channel
-    DAC_Cmd(channel, ENABLE);
+    DAC_Cmd(dac_obj->dac_channel, ENABLE);
 
     // from now on use DAC_SetChannel[12]Data to trigger a conversion
 
-    sample_buf_in = 0;
-    sample_buf_out = 0;
-
     // return static object
-    return dac_obj;
+    return (mp_obj_t)dac_obj;
 }
 
 MP_DEFINE_CONST_FUN_OBJ_1(pyb_Audio_obj, pyb_Audio);