　今回の内容は「マイコンに四声合唱をさせる」です（この話は長くかつ動作も重くなるので何回かに分けます）。

　必要と思ったことは次の５点。

１．4つの柔軟なタイマー
２．PWMの周波数をドレミのそれに合わせ変化させる
３．16ビットタイマー（60000は必要）
４．32ビットマイコン
５．使い易そうな（私が慣れてる？）STM32マイコン

　最近は、楽譜を取り込んでMIDIファイルにできるとか。そこまでは要りません。マイコンに我が青春の思い出の四部合唱をさせたいだけです。ArduinoIDEで扱えるモノの中で、4つのタイマーを持ちそれを自由に扱えそうなボードが見つからず、結局「STM32マイコン」と「STM32CubeIDE」に落ち着きました。元々は12年程前に
https://www.cqpub.co.jp/hanbai/books/31/31401.htm
上で作ったもので、その後「STM32VLDiscovery」に載せ、さらに「STM32F411 BlackPill Dev Board」に移植しました。
　なおこのボードは書込みモードへの入り方に癖があり苦労します。

うまくできればデバイスマネージャーに「STM32 BOOTLOADER」として現れます。

　「STM32CubeIDE」と専用の書込みアプリ「STM32CubeProgrammer」の話だけでも長くなるので、詳細は

などを参考にしてください。
　ここでは「STM32F411CEU6」を対象に新規プロジェクトを作成していきました。「Clock Configuration」はグラフィックで解りやすい。「Pinout & Configuration」でタイマーを4つ選びどこから出力するか決めるだけです。「Channel」はコーディングし易いように全て「TIM_CHANNEL_1」にしてあります。

難しい事はIDEがやってくれます。以下にIDEの作ってくれたmain.c（の抜粋整形）を示します。一つ一つ詳細に述べることは私も良く解ってはいないので止めておきます。こんな感じと思って頂けばよろしいかと。私が独自に書いたのは、この中の「USER Code」の部分です。特に挙げれば次の箇所。

uint16_t period;

void tone(TIM_HandleTypeDef htim,uint32_t freq ){
		period = (uint32_t)(GHz/freq);
		htim.Init.Period = period;
		HAL_TIM_Base_Init(&htim);
		__HAL_TIM_SET_COMPARE(&htim, TIM_CHANNEL_1, 30);
}

void noTone(TIM_HandleTypeDef htim){
	__HAL_TIM_SET_COMPARE(&htim, TIM_CHANNEL_1, 0);
}

これで freq を与え period にし音を出します（noTone()は音を止めます）。
　1ms毎に呼び出される「SysTick_Handler」は、通常「stm32f?xx_it.c」内にあるのですが「main.c」に入れてあります。

void SysTick_Handler(void)
{
    HAL_IncTick();

main.c

/* USER CODE BEGIN Header */
/* main.c
  Copyright (c) 2022 STMicroelectronics.
*/
/* USER CODE END Header */
/* Includes ------------------------------------------------------------------*/
#include "main.h"
/* Private includes ----------------------------------------------------------*/
/* USER CODE BEGIN Includes */
#include "onpu.h"
/* USER CODE END Includes */

/* Private typedef -----------------------------------------------------------*/
/* USER CODE BEGIN PTD */
/* USER CODE END PTD */

/* Private define ------------------------------------------------------------*/
/* USER CODE BEGIN PD */
#define GHz 4000000000  // <- Best at 12MHz
/* USER CODE END PD */

/* Private macro -------------------------------------------------------------*/
/* USER CODE BEGIN PM */
/* USER CODE END PM */

/* Private variables ---------------------------------------------------------*/
TIM_HandleTypeDef htim1;
TIM_HandleTypeDef htim2;
TIM_HandleTypeDef htim3;
TIM_HandleTypeDef htim4;

/* USER CODE BEGIN PV */
int SopCount=0;
int SopNumber=0;
int AltCount=0;
int AltNumber=0;
int TenCount=0;
int TenNumber=0;
int BasCount=0;
int BasNumber=0;
/* USER CODE END PV */

/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);
static void MX_TIM1_Init(void);
static void MX_TIM2_Init(void);
static void MX_TIM3_Init(void);
static void MX_TIM4_Init(void);
/* USER CODE BEGIN PFP */
/* USER CODE END PFP */

/* Private user code ---------------------------------------------------------*/
/* USER CODE BEGIN 0 */
uint16_t period;

void tone(TIM_HandleTypeDef htim,uint32_t freq ){
   	period = (uint32_t)(GHz/freq);
   	htim.Init.Period = period;
   	HAL_TIM_Base_Init(&htim);
   	__HAL_TIM_SET_COMPARE(&htim, TIM_CHANNEL_1, 30);
}

void noTone(TIM_HandleTypeDef htim){
   __HAL_TIM_SET_COMPARE(&htim, TIM_CHANNEL_1, 0);
}

/* USER CODE END 0 */

/*The application entry point.*/
int main(void)
{
 /* USER CODE BEGIN 1 */
 /* USER CODE END 1 */

 /* MCU Configuration--------------------------------------------------------*/

 /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
 HAL_Init();

 /* USER CODE BEGIN Init */
 /* USER CODE END Init */

 /* Configure the system clock */
 SystemClock_Config();

 /* USER CODE BEGIN SysInit */
 /* USER CODE END SysInit */

 /* Initialize all configured peripherals */
 MX_GPIO_Init();
 MX_TIM1_Init();
 MX_TIM2_Init();
 MX_TIM3_Init();
 MX_TIM4_Init();
 /* USER CODE BEGIN 2 */
 /* USER CODE END 2 */

 /* Infinite loop */
 /* USER CODE BEGIN WHILE */
 HAL_TIM_PWM_Start(&htim1,TIM_CHANNEL_1);
 HAL_TIM_PWM_Start(&htim2,TIM_CHANNEL_1);
 HAL_TIM_PWM_Start(&htim3,TIM_CHANNEL_1);
 HAL_TIM_PWM_Start(&htim4,TIM_CHANNEL_1);

 while (1)
 {
   /* USER CODE END WHILE */

   /* USER CODE BEGIN 3 */
 }
 /* USER CODE END 3 */
}

void SysTick_Handler(void)
{
   /* USER CODE BEGIN SysTick_IRQn 0 */
   /* USER CODE END SysTick_IRQn 0 */
   HAL_IncTick();
   /* USER CODE BEGIN SysTick_IRQn 1 */
   SopCount++;
   if(SopCount>sop[SopNumber][1]){
   	SopCount=0;
   	SopNumber++;
   	if(sop[SopNumber][0]==0)HAL_TIM_PWM_Stop(&htim1,TIM_CHANNEL_1);
   	if(sop[SopNumber][0]==1)noTone(htim1);
   	else tone(htim1,sop[SopNumber][0]);
   }

   AltCount++;
   if(AltCount>alt[AltNumber][1]){
   	AltCount=0;
   	AltNumber++;
   	if(alt[AltNumber][0]==0)HAL_TIM_PWM_Stop(&htim2,TIM_CHANNEL_1);
   	if(alt[AltNumber][0]==1)noTone(htim2);
   	else tone(htim2,alt[AltNumber][0]);
   }

   TenCount++;
   if(TenCount>ten[TenNumber][1]){
   	TenCount=0;
   	TenNumber++;
   	if(ten[TenNumber][0]==0)HAL_TIM_PWM_Stop(&htim3,TIM_CHANNEL_1);
   	if(ten[TenNumber][0]==1)noTone(htim3);
   	else tone(htim3,ten[TenNumber][0]);
   }

   BasCount++;
   if(BasCount>bas[BasNumber][1]){
   	BasCount=0;
   	BasNumber++;
   	if(bas[BasNumber][0]==0)HAL_TIM_PWM_Stop(&htim4,TIM_CHANNEL_1);
   	if(bas[BasNumber][0]==1)noTone(htim4);
   	else tone(htim4,bas[BasNumber][0]);
   }

 /* USER CODE END SysTick_IRQn 1 */
}

/* System Clock Configuration */
void SystemClock_Config(void)
{
 RCC_OscInitTypeDef RCC_OscInitStruct = {0};
 RCC_ClkInitTypeDef RCC_ClkInitStruct = {0};

 /* Configure the main internal regulator output voltage */
 __HAL_RCC_PWR_CLK_ENABLE();
 __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);

 /** Initializes the RCC Oscillators according to the specified parameters
 * in the RCC_OscInitTypeDef structure. */
 RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSI;
 RCC_OscInitStruct.HSIState = RCC_HSI_ON;
 RCC_OscInitStruct.HSICalibrationValue = RCC_HSICALIBRATION_DEFAULT;
 RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
 RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSI;
 RCC_OscInitStruct.PLL.PLLM = 8;
 RCC_OscInitStruct.PLL.PLLN = 72;
 RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV6;
 RCC_OscInitStruct.PLL.PLLQ = 4;
 if (HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
 {
   Error_Handler();
 }

 /** Initializes the CPU, AHB and APB buses clocks */
 RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_HCLK|RCC_CLOCKTYPE_SYSCLK
                             |RCC_CLOCKTYPE_PCLK1|RCC_CLOCKTYPE_PCLK2;
 RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
 RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
 RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV2;
 RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV1;

 if (HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_0) != HAL_OK)
 {
   Error_Handler();
 }
}

/* TIM1 Initialization Function */
static void MX_TIM1_Init(void)
{
 /* USER CODE BEGIN TIM1_Init 0 */
 /* USER CODE END TIM1_Init 0 */

 TIM_ClockConfigTypeDef sClockSourceConfig = {0};
 TIM_MasterConfigTypeDef sMasterConfig = {0};
 TIM_OC_InitTypeDef sConfigOC = {0};
 TIM_BreakDeadTimeConfigTypeDef sBreakDeadTimeConfig = {0};

 /* USER CODE BEGIN TIM1_Init 1 */
 /* USER CODE END TIM1_Init 1 */

 htim1.Instance = TIM1;
 htim1.Init.Prescaler = 6-1;
 htim1.Init.CounterMode = TIM_COUNTERMODE_UP;
 htim1.Init.Period = 1760-1;
 htim1.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
 htim1.Init.RepetitionCounter = 0;
 htim1.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
 if (HAL_TIM_Base_Init(&htim1) != HAL_OK)
 {
   Error_Handler();
 }
 sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
 if (HAL_TIM_ConfigClockSource(&htim1, &sClockSourceConfig) != HAL_OK)
 {
   Error_Handler();
 }
 if (HAL_TIM_PWM_Init(&htim1) != HAL_OK)
 {
   Error_Handler();
 }
 sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
 sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
 if (HAL_TIMEx_MasterConfigSynchronization(&htim1, &sMasterConfig) != HAL_OK)
 {
   Error_Handler();
 }
 sConfigOC.OCMode = TIM_OCMODE_PWM1;
 sConfigOC.Pulse = 0;
 sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;
 sConfigOC.OCNPolarity = TIM_OCNPOLARITY_HIGH;
 sConfigOC.OCFastMode = TIM_OCFAST_DISABLE;
 sConfigOC.OCIdleState = TIM_OCIDLESTATE_RESET;
 sConfigOC.OCNIdleState = TIM_OCNIDLESTATE_RESET;
 if (HAL_TIM_PWM_ConfigChannel(&htim1, &sConfigOC, TIM_CHANNEL_1) != HAL_OK)
 {
   Error_Handler();
 }
 sBreakDeadTimeConfig.OffStateRunMode = TIM_OSSR_DISABLE;
 sBreakDeadTimeConfig.OffStateIDLEMode = TIM_OSSI_DISABLE;
 sBreakDeadTimeConfig.LockLevel = TIM_LOCKLEVEL_OFF;
 sBreakDeadTimeConfig.DeadTime = 0;
 sBreakDeadTimeConfig.BreakState = TIM_BREAK_DISABLE;
 sBreakDeadTimeConfig.BreakPolarity = TIM_BREAKPOLARITY_HIGH;
 sBreakDeadTimeConfig.AutomaticOutput = TIM_AUTOMATICOUTPUT_DISABLE;
 if (HAL_TIMEx_ConfigBreakDeadTime(&htim1, &sBreakDeadTimeConfig) != HAL_OK)
 {
   Error_Handler();
 }
 /* USER CODE BEGIN TIM1_Init 2 */
 /* USER CODE END TIM1_Init 2 */
 HAL_TIM_MspPostInit(&htim1);
}

/* TIM2 Initialization Function */
static void MX_TIM2_Init(void)
{
 /* USER CODE BEGIN TIM2_Init 0 */
 /* USER CODE END TIM2_Init 0 */

 TIM_ClockConfigTypeDef sClockSourceConfig = {0};
 TIM_MasterConfigTypeDef sMasterConfig = {0};
 TIM_OC_InitTypeDef sConfigOC = {0};

 /* USER CODE BEGIN TIM2_Init 1 */
 /* USER CODE END TIM2_Init 1 */
 htim2.Instance = TIM2;
 htim2.Init.Prescaler = 6-1;
 htim2.Init.CounterMode = TIM_COUNTERMODE_UP;
 htim2.Init.Period = 1760-1;
 htim2.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
 htim2.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
 if (HAL_TIM_Base_Init(&htim2) != HAL_OK)
 {
   Error_Handler();
 }
 sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
 if (HAL_TIM_ConfigClockSource(&htim2, &sClockSourceConfig) != HAL_OK)
 {
   Error_Handler();
 }
 if (HAL_TIM_PWM_Init(&htim2) != HAL_OK)
 {
   Error_Handler();
 }
 sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
 sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
 if (HAL_TIMEx_MasterConfigSynchronization(&htim2, &sMasterConfig) != HAL_OK)
 {
   Error_Handler();
 }
 sConfigOC.OCMode = TIM_OCMODE_PWM1;
 sConfigOC.Pulse = 0;
 sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;
 sConfigOC.OCFastMode = TIM_OCFAST_DISABLE;
 if (HAL_TIM_PWM_ConfigChannel(&htim2, &sConfigOC, TIM_CHANNEL_1) != HAL_OK)
 {
   Error_Handler();
 }
 /* USER CODE BEGIN TIM2_Init 2 */
 /* USER CODE END TIM2_Init 2 */
 HAL_TIM_MspPostInit(&htim2);
}

/* TIM3 Initialization Function */
static void MX_TIM3_Init(void)
{
 /* USER CODE BEGIN TIM3_Init 0 */
 /* USER CODE END TIM3_Init 0 */

 TIM_ClockConfigTypeDef sClockSourceConfig = {0};
 TIM_MasterConfigTypeDef sMasterConfig = {0};
 TIM_OC_InitTypeDef sConfigOC = {0};

 /* USER CODE BEGIN TIM3_Init 1 */
 /* USER CODE END TIM3_Init 1 */
 htim3.Instance = TIM3;
 htim3.Init.Prescaler = 6-1;
 htim3.Init.CounterMode = TIM_COUNTERMODE_UP;
 htim3.Init.Period = 1760-1;
 htim3.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
 htim3.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
 if (HAL_TIM_Base_Init(&htim3) != HAL_OK)
 {
   Error_Handler();
 }
 sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
 if (HAL_TIM_ConfigClockSource(&htim3, &sClockSourceConfig) != HAL_OK)
 {
   Error_Handler();
 }
 if (HAL_TIM_PWM_Init(&htim3) != HAL_OK)
 {
   Error_Handler();
 }
 sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
 sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
 if (HAL_TIMEx_MasterConfigSynchronization(&htim3, &sMasterConfig) != HAL_OK)
 {
   Error_Handler();
 }
 sConfigOC.OCMode = TIM_OCMODE_PWM1;
 sConfigOC.Pulse = 0;
 sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;
 sConfigOC.OCFastMode = TIM_OCFAST_DISABLE;
 if (HAL_TIM_PWM_ConfigChannel(&htim3, &sConfigOC, TIM_CHANNEL_1) != HAL_OK)
 {
   Error_Handler();
 }
 /* USER CODE BEGIN TIM3_Init 2 */
 /* USER CODE END TIM3_Init 2 */
 HAL_TIM_MspPostInit(&htim3);
}

/* TIM4 Initialization Function */
static void MX_TIM4_Init(void)
{
 /* USER CODE BEGIN TIM4_Init 0 */
 /* USER CODE END TIM4_Init 0 */
 TIM_ClockConfigTypeDef sClockSourceConfig = {0};
 TIM_MasterConfigTypeDef sMasterConfig = {0};
 TIM_OC_InitTypeDef sConfigOC = {0};
 /* USER CODE BEGIN TIM4_Init 1 */
 /* USER CODE END TIM4_Init 1 */
 htim4.Instance = TIM4;
 htim4.Init.Prescaler = 6-1;
 htim4.Init.CounterMode = TIM_COUNTERMODE_UP;
 htim4.Init.Period = 1760-1;
 htim4.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
 htim4.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
 if (HAL_TIM_Base_Init(&htim4) != HAL_OK)
 {
   Error_Handler();
 }
 sClockSourceConfig.ClockSource = TIM_CLOCKSOURCE_INTERNAL;
 if (HAL_TIM_ConfigClockSource(&htim4, &sClockSourceConfig) != HAL_OK)
 {
   Error_Handler();
 }
 if (HAL_TIM_PWM_Init(&htim4) != HAL_OK)
 {
   Error_Handler();
 }
 sMasterConfig.MasterOutputTrigger = TIM_TRGO_RESET;
 sMasterConfig.MasterSlaveMode = TIM_MASTERSLAVEMODE_DISABLE;
 if (HAL_TIMEx_MasterConfigSynchronization(&htim4, &sMasterConfig) != HAL_OK)
 {
   Error_Handler();
 }
 sConfigOC.OCMode = TIM_OCMODE_PWM1;
 sConfigOC.Pulse = 0;
 sConfigOC.OCPolarity = TIM_OCPOLARITY_HIGH;
 sConfigOC.OCFastMode = TIM_OCFAST_DISABLE;
 if (HAL_TIM_PWM_ConfigChannel(&htim4, &sConfigOC, TIM_CHANNEL_1) != HAL_OK)
 {
   Error_Handler();
 }
 /* USER CODE BEGIN TIM4_Init 2 */
 /* USER CODE END TIM4_Init 2 */
 HAL_TIM_MspPostInit(&htim4);
}

/* GPIO Initialization Function */
static void MX_GPIO_Init(void)
{
 /* GPIO Ports Clock Enable */
 __HAL_RCC_GPIOA_CLK_ENABLE();
 __HAL_RCC_GPIOB_CLK_ENABLE();
}

/* USER CODE BEGIN 4 */
/* USER CODE END 4 */

/* This function is executed in case of error occurrence. */
void Error_Handler(void)
{
// 以下略

長くなりましたので、今回はここまでにして次回に続きます。ここまで見てくださり有難うございました。