stmhal: Add ADC function to read data at a given frequency.

Reads ADC values into a bytearray (or similar) at a fixed rate.  Needs a
better name and improved API.  Also fix up DAC dma function (which also
needs a better name and API).

stmhal/adc.c

@@ -11,6 +11,7 @@
 #include "adc.h"
 #include "pin.h"
 #include "build/pins.h"
+#include "timer.h"
 
 // Usage Model:
 //
@@ -162,8 +163,39 @@ STATIC mp_obj_t adc_read(mp_obj_t self_in) {
 
 STATIC MP_DEFINE_CONST_FUN_OBJ_1(adc_read_obj, adc_read);
 
+STATIC mp_obj_t adc_read_timed(mp_obj_t self_in, mp_obj_t buf_in, mp_obj_t freq_in) {
+    pyb_obj_adc_t *self = self_in;
+
+    buffer_info_t bufinfo;
+    mp_get_buffer_raise(buf_in, &bufinfo);
+
+    // Init TIM6 at the required frequency (in Hz)
+    timer_tim6_init(mp_obj_get_int(freq_in));
+
+    // Start timer
+    HAL_TIM_Base_Start(&TIM6_Handle);
+
+    // This uses the timer in polling mode to do the sampling
+    // TODO use DMA
+    for (uint i = 0; i < bufinfo.len; i++) {
+        // Wait for the timer to trigger
+        while (__HAL_TIM_GET_FLAG(&TIM6_Handle, TIM_FLAG_UPDATE) == RESET) {
+        }
+        __HAL_TIM_CLEAR_FLAG(&TIM6_Handle, TIM_FLAG_UPDATE);
+        ((byte*)bufinfo.buf)[i] = adc_read_channel(&self->handle) >> 4;
+    }
+
+    // Stop timer
+    HAL_TIM_Base_Stop(&TIM6_Handle);
+
+    return mp_obj_new_int(bufinfo.len);
+}
+
+STATIC MP_DEFINE_CONST_FUN_OBJ_3(adc_read_timed_obj, adc_read_timed);
+
 STATIC const mp_map_elem_t adc_locals_dict_table[] = {
     { MP_OBJ_NEW_QSTR(MP_QSTR_read), (mp_obj_t)&adc_read_obj},
+    { MP_OBJ_NEW_QSTR(MP_QSTR_read_timed), (mp_obj_t)&adc_read_timed_obj},
 };
 
 STATIC MP_DEFINE_CONST_DICT(adc_locals_dict, adc_locals_dict_table);

stmhal/dac.c

@@ -10,9 +10,9 @@
 #include "parse.h"
 #include "obj.h"
 #include "runtime.h"
+#include "timer.h"
 #include "dac.h"
 
-TIM_HandleTypeDef TIM6_Handle;
 STATIC DAC_HandleTypeDef DAC_Handle;
 
 void dac_init(void) {
@@ -22,19 +22,8 @@ void dac_init(void) {
 }
 
 STATIC void TIM6_Config(uint freq) {
-    // TIM6 clock enable
-    __TIM6_CLK_ENABLE();
-
-    // Compute the prescaler value so TIM6 triggers at freq-Hz
-    uint16_t period = (uint16_t) ((SystemCoreClock / 2) / freq) - 1;
-
-    // time base clock configuration
-    TIM6_Handle.Instance = TIM6;
-    TIM6_Handle.Init.Period = period;
-    TIM6_Handle.Init.Prescaler = 0; // timer runs at SystemCoreClock / 2
-    TIM6_Handle.Init.ClockDivision = 0; // unused for TIM6
-    TIM6_Handle.Init.CounterMode = TIM_COUNTERMODE_UP; // unused for TIM6
-    HAL_TIM_Base_Init(&TIM6_Handle);
+    // Init TIM6 at the required frequency (in Hz)
+    timer_tim6_init(freq);
 
     // TIM6 TRGO selection
     TIM_MasterConfigTypeDef config;
@@ -203,17 +192,14 @@ mp_obj_t pyb_dac_dma(uint n_args, const mp_obj_t *args, mp_map_t *kw_args) {
     DAC_Init(self->dac_channel, &DAC_InitStructure);
     */
 
-    if (self->state != 3) {
-        DAC_ChannelConfTypeDef config;
-        config.DAC_Trigger = DAC_TRIGGER_T6_TRGO;
-        config.DAC_OutputBuffer = DAC_OUTPUTBUFFER_ENABLE;
-        HAL_DAC_ConfigChannel(&DAC_Handle, &config, self->dac_channel);
-        self->state = 3;
-    }
-
     // DMA1_Stream[67] channel7 configuration
     DMA_HandleTypeDef DMA_Handle;
     DMA_Handle.Instance = self->dma_stream;
+
+    // Need to deinit DMA first
+    DMA_Handle.State = HAL_DMA_STATE_READY;
+    HAL_DMA_DeInit(&DMA_Handle);
+
     DMA_Handle.Init.Channel = DMA_CHANNEL_7;
     DMA_Handle.Init.Direction = DMA_MEMORY_TO_PERIPH;
     DMA_Handle.Init.PeriphInc = DMA_PINC_DISABLE;
@@ -231,6 +217,18 @@ mp_obj_t pyb_dac_dma(uint n_args, const mp_obj_t *args, mp_map_t *kw_args) {
 
     __HAL_LINKDMA(&DAC_Handle, DMA_Handle1, DMA_Handle);
 
+    DAC_Handle.Instance = DAC;
+    DAC_Handle.State = HAL_DAC_STATE_RESET;
+    HAL_DAC_Init(&DAC_Handle);
+
+    if (self->state != 3) {
+        DAC_ChannelConfTypeDef config;
+        config.DAC_Trigger = DAC_TRIGGER_T6_TRGO;
+        config.DAC_OutputBuffer = DAC_OUTPUTBUFFER_ENABLE;
+        HAL_DAC_ConfigChannel(&DAC_Handle, &config, self->dac_channel);
+        self->state = 3;
+    }
+
     HAL_DAC_Start_DMA(&DAC_Handle, self->dac_channel, (uint32_t*)bufinfo.buf, bufinfo.len, DAC_ALIGN_8B_R);
 
     /*

stmhal/qstrdefsport.h

@@ -97,6 +97,7 @@ Q(filtered_xyz)
 // for ADC object
 Q(ADC)
 Q(ADC_all)
+Q(read_timed)
 Q(read_channel)
 Q(read_core_temp)
 Q(read_core_vbat)

stmhal/timer.c

@@ -27,6 +27,7 @@
 
 TIM_HandleTypeDef TIM3_Handle;
 TIM_HandleTypeDef TIM5_Handle;
+TIM_HandleTypeDef TIM6_Handle;
 
 // TIM3 is set-up for the USB CDC interface
 void timer_tim3_init(void) {
@@ -57,6 +58,7 @@ void timer_tim3_deinit(void) {
 */
 
 // TIM5 is set-up for the servo controller
+// This function inits but does not start the timer
 void timer_tim5_init(void) {
     // TIM5 clock enable
     __TIM5_CLK_ENABLE();
@@ -74,6 +76,31 @@ void timer_tim5_init(void) {
     HAL_TIM_PWM_Init(&TIM5_Handle);
 }
 
+// Init TIM6 with a counter-overflow at the given frequency (given in Hz)
+// TIM6 is used by the DAC and ADC for auto sampling at a given frequency
+// This function inits but does not start the timer
+void timer_tim6_init(uint freq) {
+    // TIM6 clock enable
+    __TIM6_CLK_ENABLE();
+
+    // Timer runs at SystemCoreClock / 2
+    // Compute the prescaler value so TIM6 triggers at freq-Hz
+    uint32_t period = (SystemCoreClock / 2) / freq;
+    uint32_t prescaler = 1;
+    while (period > 0xffff) {
+        period >>= 1;
+        prescaler <<= 1;
+    }
+
+    // Time base clock configuration
+    TIM6_Handle.Instance = TIM6;
+    TIM6_Handle.Init.Period = period - 1;
+    TIM6_Handle.Init.Prescaler = prescaler - 1;
+    TIM6_Handle.Init.ClockDivision = 0; // unused for TIM6
+    TIM6_Handle.Init.CounterMode = TIM_COUNTERMODE_UP; // unused for TIM6
+    HAL_TIM_Base_Init(&TIM6_Handle);
+}
+
 // Interrupt dispatch
 void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim) {
     if (htim == &TIM3_Handle) {

stmhal/timer.h

@@ -5,6 +5,8 @@
 
 extern TIM_HandleTypeDef TIM3_Handle;
 extern TIM_HandleTypeDef TIM5_Handle;
+extern TIM_HandleTypeDef TIM6_Handle;
 
 void timer_tim3_init(void);
 void timer_tim5_init(void);
+void timer_tim6_init(uint freq);