Configure channel 2 of the DFSDM peripheral with system clock as fDFSDM clock source, DFSDM clock divider D =57, oversampling ratio R = 64, continuous conversion mode. Write a program to record the samples from digital microphone over 2 seconds and implement the playback of the recorded data using timer TIM7 and microcontroller internal DAC. Connect DAC output pin to the external amplifier board with a speaker. Turn on LD5 green LED to indicate recording phase, turn it off while the recorded samples are played back.

Question

Configure channel 2 of the DFSDM peripheral with system clock as fDFSDM clock source, DFSDM clock divider D =57, oversampling ratio R = 64, continuous conversion mode. Write a program to record the samples from digital microphone over 2 seconds and implement the playback of the recorded data using timer TIM7 and microcontroller internal DAC. Connect DAC output pin to the external amplifier board with a speaker. Turn on LD5 green LED to indicate recording phase, turn it off while the recorded samples are played back.

2. Determine the amount of memory buffer (in bytes) required for the specified duration of audio recording using DFSDM configuration data from question 1, if the audio samples are stored with 16-bit resolution. Show all your work.

Answer 1

First, let's determine the DFSDM Clock frequency f_DFSDM:

f_DFSDM = System Clock / (Clock Divider + 1)

Assuming that the system clock frequency is given, the f_DFSDM can be calculated as follows:

f_DFSDM = System Clock / (57 + 1)

To find the output data rate f_output:

f_output = f_DFSDM / [(Clock Divider) * (Oversampling Ratio)]

Since we have a 16-bit resolution, 2 bytes are required to store one sample. The amount of memory needed to record the samples for 2 seconds can be computed:

Buffer Size (bytes) = f_output * 2 * recording_time

Now, let's write the program to record the samples and initiate playback using TIM7 and the internal DAC.

```c
#include "stm32f4xx_hal.h"

// Declarations
void DFSDM_Init(void);
void TIM7_Init(void);
void DAC_Init(void);
void Record_and_Playback(void);

uint16_t buffer[2 * Buffer_Size];
uint32_t current_sample;

int main(void) {
HAL_Init();
SystemClock_Config();

DFSDM_Init();
TIM7_Init();
DAC_Init();

Record_and_Playback();

while (1)
;

return 0;
}

void DFSDM_Init(void) {
// Configure and enable DFSDM channel 2 with system clock as fDFSDM clock source,
// DFSDM clock divider 57, oversampling ratio 64, continuous conversion mode.
// (Assuming the DFSDM configuration is not already done)
// ...
}

void TIM7_Init(void) {
// Configure and enable TIM7 to trigger DAC at the output data rate f_output
// (Assuming the TIMER7 configuration is not already done)
// ...
}

void DAC_Init(void) {
// Configure and enable the internal DAC
// (Assuming the DAC configuration is not already done)
// ...
}

void Record_and_Playback(void) {
// Enable LED indicator for recording
HAL_GPIO_WritePin(LD5_GPIO_Port, LD5_Pin, GPIO_PIN_SET);

// Record samples for 2 seconds
for (current_sample = 0; current_sample < 2 * Buffer_Size; current_sample++) {
buffer[current_sample] = HAL_DFSDM_FilterPolling(DFSDM_CHANNEL_2, 0xFFFF);
}

// Disable LED indicator after recording
HAL_GPIO_WritePin(LD5_GPIO_Port, LD5_Pin, GPIO_PIN_RESET);

// Start TIM7 to trigger DAC
HAL_TIM_Base_Start(&htim7);

// Playback the recorded samples using internal DAC
for (current_sample = 0; current_sample < 2 * Buffer_Size; current_sample++) {
HAL_DAC_SetValue(&hdac, DAC_CHANNEL_x, DAC_ALIGN_12B_R, buffer[current_sample]);
HAL_DAC_Start(&hdac, DAC_CHANNEL_x);
}
}
```

Replace "Buffer_Size" with the actual number of buffer data calculated above based on the f_output data rate.