From c723f59ecc27505566d54d9edde0bdb98a5623b1 Mon Sep 17 00:00:00 2001
From: Clyne Sullivan <clyne@bitgloo.com>
Date: Thu, 30 Jan 2025 08:14:20 -0500
Subject: decibel measuring?

---
 Core/Src/main.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 53 insertions(+), 12 deletions(-)

(limited to 'Core/Src')

diff --git a/Core/Src/main.c b/Core/Src/main.c
index aa520a3..6b7fad0 100644
--- a/Core/Src/main.c
+++ b/Core/Src/main.c
@@ -22,18 +22,23 @@
 /* Private includes ----------------------------------------------------------*/
 /* USER CODE BEGIN Includes */
 #include <stdio.h>
+#include <qfplib-port.h>
 /* USER CODE END Includes */
 
 /* Private typedef -----------------------------------------------------------*/
 /* USER CODE BEGIN PTD */
-typedef struct {
+typedef struct  {
     int32_t value : 18;
 } sample_t;
 /* USER CODE END PTD */
 
 /* Private define ------------------------------------------------------------*/
 /* USER CODE BEGIN PD */
-
+#define SAMPLE_COUNT    (512)   // Sample count per half-transfer
+#define MIC_OFFSET_DB   (  0.f) // Linear offset
+#define MIC_SENSITIVITY (-26.f) // dBFS value expected at MIC_REF_DB
+#define MIC_REF_DB      ( 94.f) // dB where sensitivity is specified
+#define MIC_BITS        (18)
 /* USER CODE END PD */
 
 /* Private macro -------------------------------------------------------------*/
@@ -50,10 +55,16 @@ DMA_HandleTypeDef hdma_spi1_tx;
 UART_HandleTypeDef huart2;
 
 /* USER CODE BEGIN PV */
-static /*const*/ uint8_t I2S_Frame_Buffer[8] = {
+static const uint8_t I2S_Frame_Buffer[8] = {
   0x00, 0x00, 0x00, 0x00, 0xFF, 0xFF, 0xFF, 0xFF
 };
-static uint8_t I2S_Receive_Buffer[4096];
+static uint8_t I2S_Receive_Buffer[SAMPLE_COUNT * sizeof(sample_t)];
+
+float ln10;
+float MIC_REF_AMPL;
+
+static float DB_Sum_Squares = 0.f;
+static unsigned DB_Count = 0;
 /* USER CODE END PV */
 
 /* Private function prototypes -----------------------------------------------*/
@@ -65,7 +76,7 @@ static void MX_USART2_UART_Init(void);
 /* USER CODE BEGIN PFP */
 static HAL_StatusTypeDef HAL_SPI_TransmitReceive_DMA_Mixed(
     SPI_HandleTypeDef *hspi,
-    uint8_t *pTxData,
+    const uint8_t *pTxData,
     uint8_t *pRxData,
     uint16_t TxSize,
     uint16_t RxSize);
@@ -91,7 +102,9 @@ int main(void)
 {
 
   /* USER CODE BEGIN 1 */
-
+  ln10 = qfp_fln(10.f);
+  MIC_REF_AMPL = qfp_fmul(qfp_int2float((1 << (MIC_BITS - 1)) - 1),
+    qfp_fpow(10.f, MIC_SENSITIVITY / 20.f));
   /* USER CODE END 1 */
 
   /* MCU Configuration--------------------------------------------------------*/
@@ -426,7 +439,7 @@ static void MX_GPIO_Init(void)
 /* USER CODE BEGIN 4 */
 HAL_StatusTypeDef HAL_SPI_TransmitReceive_DMA_Mixed(
     SPI_HandleTypeDef *hspi,
-    uint8_t *pTxData,
+    const uint8_t *pTxData,
     uint8_t *pRxData,
     uint16_t TxSize,
     uint16_t RxSize)
@@ -507,13 +520,44 @@ void SPI_DMATransmitReceiveCplt(DMA_HandleTypeDef *hdma)
   (void)hspi;
 }
 
+static float process(float in_div4)
+{
+    static float z1 = 0, z2 = 0, z3 = 0, z5 = 0;
+
+    float out1 = qfp_fadd(in_div4, z1);
+    z1 = qfp_fadd(qfp_fmul(1.062f, out1), z2);
+    z2 = qfp_fsub(qfp_fmul(-0.14f, out1), in_div4);
+
+    float out2 = qfp_fadd(out1, z3);
+    z3 = out1;
+
+    float out3 = qfp_fadd(out2, z5);
+    z5 = qfp_fsub(qfp_fmul(0.985f, out3), out2);
+
+    return out3;
+}
+
 void SPI_DMAHalfTransmitReceiveCplt(DMA_HandleTypeDef *hdma)
 {
   SPI_HandleTypeDef *hspi = (SPI_HandleTypeDef *)hdma->Parent;
   (void)hspi;
 
-  sample_t sample = *(sample_t *)I2S_Receive_Buffer;
-  printf("%d\r\n", sample.value);
+  sample_t *sample = (sample_t *)I2S_Receive_Buffer;
+  for (int i = 0; i < SAMPLE_COUNT / 8; i++) {
+    float f = process(qfp_int2float(sample[i].value / 4));
+    DB_Sum_Squares = qfp_fadd(DB_Sum_Squares, qfp_fmul(f, f));
+  }
+  DB_Count += SAMPLE_COUNT / 8;
+
+  if (DB_Count > 48000 / 4) {
+    float rms = qfp_fsqrt(qfp_fdiv(DB_Sum_Squares, qfp_uint2float(DB_Count)));
+    float db = qfp_fadd(MIC_OFFSET_DB + MIC_REF_DB, qfp_fmul(20.f,
+      qfp_flog10(qfp_fdiv(rms, MIC_REF_AMPL))));
+    DB_Sum_Squares = 0.f;
+    DB_Count = 0;
+
+    printf("%d\r\n", qfp_float2int(db));
+  }
 }
 /* USER CODE END 4 */
 
@@ -524,7 +568,6 @@ void SPI_DMAHalfTransmitReceiveCplt(DMA_HandleTypeDef *hdma)
 void Error_Handler(void)
 {
   /* USER CODE BEGIN Error_Handler_Debug */
-  /* User can add his own implementation to report the HAL error return state */
   __disable_irq();
   printf("Unhandled error, halting!\r\n");
   while (1)
@@ -544,8 +587,6 @@ void Error_Handler(void)
 void assert_failed(uint8_t *file, uint32_t line)
 {
   /* USER CODE BEGIN 6 */
-  /* User can add his own implementation to report the file name and line number,
-     ex: printf("Wrong parameters value: file %s on line %d\r\n", file, line) */
   printf("Wrong parameters value: file %s on line %d\r\n", file, line);
   /* USER CODE END 6 */
 }
-- 
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