目的
I2Cだと約20cmから約30cmと伝送距離が短いので
シリアルを使い伝送距離(約2mから3m)を延ばす。

STM32G031のスレーブ




//ser_slave_ir_length_031_1


#include <Arduino.h>


#define DW   digitalWrite
#define TX1        PA0   // 4pin
#define UART_DELAY 106  // 012-110 9600bps ok 031

//仮想シリアルへの一文字出力 9600bps
void putcNS(char ch)
{
  DW(TX1, HIGH);

  DW(TX1, LOW);//START
  delayMicroseconds(UART_DELAY); //START BIT WAIT

  for (int ii = 0; ii < 8; ii++) {
    DW(TX1, (ch >> ii) & 1  );
    delayMicroseconds(UART_DELAY); //DATA 1-8BIT WAIT
  }//for

  DW(TX1, HIGH);//Stop
  delayMicroseconds(UART_DELAY); //StOP BIT WAIT

}//putcNS


//80-20
unsigned char qq[] = {
  80, 78, 77, 76, 75, 75, 74, 73, 72, 71,
  70, 69, 68, 68, 67, 66, 65, 65, 64, 63,
  63, 62, 61, 61, 60, 60, 59, 58, 58, 57,
  57, 56, 56, 55, 55, 54, 54, 53, 53, 52,
  52, 51, 51, 50, 50, 50, 49, 49, 48, 48,
  47, 47, 47, 46, 46, 46, 45, 45, 45, 44,
  44, 44, 43, 43, 43, 42, 42, 42, 41, 41,
  41, 41, 40, 40, 40, 40, 39, 39, 39, 38,
  38, 38, 38, 37, 37, 37, 37, 37, 36, 36,
  36, 36, 35, 35, 35, 35, 35, 34, 34, 34,
  34, 34, 33, 33, 33, 33, 33, 32, 32, 32,
  32, 32, 32, 31, 31, 31, 31, 31, 31, 30,
  30, 30, 30, 30, 30, 30, 29, 29, 29, 29,
  29, 29, 28, 28, 28, 28, 28, 28, 28, 28,
  27, 27, 27, 27, 27, 27, 27, 27, 26, 26,
  26, 26, 26, 26, 26, 26, 25, 25, 25, 25,
  25, 25, 25, 25, 25, 25, 24, 24, 24, 24,
  24, 24, 24, 24, 24, 24, 23, 23, 23, 23,
  23, 23, 23, 23, 23, 23, 22, 22, 22, 22,
  22, 22, 22, 22, 22, 22, 22, 22, 21, 21,
  21, 21, 21, 21, 21, 21, 21, 21, 21, 21,
  21, 20, 20, 20, 20, 20, 20, 20, 20, 20,
  20, 20, 20, 20, 20, 20
};

//20-10
unsigned char pp[] = {
  200, 199, 198, 197, 196, 196, 195, 194, 193, 193,
  192, 191, 190, 190, 189, 188, 187, 187, 186, 185,
  185, 184, 183, 183, 182, 181, 181, 180, 179, 179,
  178, 177, 177, 176, 176, 175, 174, 174, 173, 173,
  172, 171, 171, 170, 170, 169, 168, 168, 167, 167,
  166, 166, 165, 165, 164, 163, 163, 162, 162, 161,
  161, 160, 160, 159, 159, 158, 158, 157, 157, 156,
  156, 155, 155, 154, 154, 153, 153, 152, 152, 151,
  151, 151, 150, 150, 149, 149, 148, 148, 147, 147,
  147, 146, 146, 145, 145, 144, 144, 144, 143, 143,
  142, 142, 142, 141, 141, 140, 140, 140, 139, 139,
  138, 138, 138, 137, 137, 136, 136, 136, 135, 135,
  135, 134, 134, 134, 133, 133, 132, 132, 132, 131,
  131, 131, 130, 130, 130, 129, 129, 129, 128, 128,
  128, 127, 127, 127, 126, 126, 126, 125, 125, 125,
  125, 124, 124, 124, 123, 123, 123, 122, 122, 122,
  121, 121, 121, 121, 120, 120, 120, 119, 119, 119,
  119, 118, 118, 118, 117, 117, 117, 117, 116, 116,
  116, 116, 115, 115, 115, 114, 114, 114, 114, 113,
  113, 113, 113, 112, 112, 112, 112, 111, 111, 111,
  111, 110, 110, 110, 110, 109, 109, 109, 109, 108,
  108, 108, 108, 107, 107, 107, 107, 107, 106, 106,
  106, 106, 105, 105, 105, 105, 105, 104, 104, 104,
  104, 103, 103, 103, 103, 103, 102, 102, 102, 102,
  102, 101, 101, 101, 101, 101, 100, 100, 100, 100,
  100
};

//10-6
unsigned char oo[] = {
  100, 99, 98, 98, 97, 97, 96, 96, 95, 95,
  94, 94, 93, 93, 92, 92, 91, 91, 90, 90,
  90, 89, 89, 88, 88, 87, 87, 86, 86, 86,
  85, 85, 84, 84, 84, 83, 83, 82, 82, 82,
  81, 81, 81, 80, 80, 80, 79, 79, 78, 78,
  77, 77, 76, 76, 75, 75, 74, 74, 74, 73,
  73, 72, 72, 71, 71, 71, 70, 70, 69, 69,
  68, 67, 66, 66, 65, 64, 63, 63, 62, 61,
  61, 60, 60
};

//赤外線距離センサー(GP2Y0A21YK)の電圧から距離を求める。
//Voltage //電圧
int ir_len_i(int Voltage)
{

  int ir_length;   //長さ

  if (Voltage >= 0    && Voltage <= 400 ) {
    return (800);
  }
  if (Voltage >= 3120 && Voltage <= 5000) {
    return (60);
  }

  if        (Voltage >= 400 && Voltage <= 1300 ) { //80-20

    ir_length = (int)qq[(Voltage - 400) >> 2];
    ir_length = ir_length * 10;

  } else if (Voltage >= 1300 && Voltage <= 2300 ) { //20-10

    ir_length = (int)pp[(Voltage - 1300) >> 2];

  } else if (Voltage >= 2300 && Voltage <= 3120  ) { //10-6

    //ir_length = (int)oo[(Voltage - 2300) / 10];
    ir_length = (int)oo[  ((Voltage - 2300) * 205) >> 11 ]; //10の割り算

  }//end if

  //戻り値
  return (ir_length);

} //ir_le_i


void setup() {

  //TXポートの初期化
  pinMode(TX1, OUTPUT);
  DW(TX1, HIGH);

  //開始、立下りトリガー
  pinMode(PA11, INPUT);

}//setup

//10の割り算 0から1028までは、正しい。主に0から999
#define DIV10(n) ((n*205)>>11)

byte b = 200; // ((s-140)*10)+200 -> 800


void loop() {

//debug
//while(1){
//  rx_Event();
//  delay(500);
//}

  int input_bk;
  int input;
  //無限ループ
  while (1) {

    //開始信号の入力
    input = digitalRead(PA11);

    //エッジ検出　信号が変わる
    //立ち上がり、立下りの検出
    if (input != input_bk) {

      //立下り
      if ( input == LOW ) {
        delay(2); //空読み時間

        //b = '0';
        //putcNS(b);
        rx_Event();
      }//end if

    }//end if

    //信号の保存
    input_bk = input;

  }//while

}//loop


void rx_Event() {

  //PB7 入力
  //RX  PA11  11ピン G031
  //TX  PA0    4ピン G031

  ///////PB7 入力
  ///////RX  PA10  6ピン G031
  ///////TX  PA9   5ピン G031


  //ソフトウェアシリアルから距離を出力
  putcNS(b);

/*
  //debug
  char rt[16];
  rt[2] = '0' + (b - DIV10(b) * 10);
  b = DIV10(b);
  rt[1] = '0' + (b - DIV10(b) * 10);
  rt[0] = '0' + DIV10(b);
  putcNS(rt[0]);
  putcNS(rt[1]);
  putcNS(rt[2]);
  putcNS('\r');
  putcNS('\n');
  //delay(1000);
*/

  int sensorValue; //センサーの読み取り値
  int Voltage;     //電圧
  int ir_length;   //長さ

  //アナログ値の読み込み
  analogReadResolution(12); //adc 12bit mode
  sensorValue = analogRead(A9); // PB7  PIN1 031

  //アナログ値を電圧に変換
  Voltage = (sensorValue * 3300) >> 12; //stm32　(s*3300)/4096
  if (Voltage > 5000) {
    Voltage = 5000; //アナログ変換エラー対策
  }//end if
  if (Voltage < 0   ) {
    Voltage = 0;
  }//end if
  //Voltage = 1300;//debug


  //赤外線距離センサー(GP2Y0A21YK)の電圧から距離を求める。
  ir_length = ir_len_i(Voltage);

  //ir_length = 210;

  if ( ir_length <= 199 ) {

    b = ir_length - 60;

  } else {

    b = (byte)(   DIV10(ir_length) - 20 + 140 );

  }

  //b = 200;//debug
  //b = '0';//debug

}//rx_Event

Arduino UNOのマスター



#include <Arduino.h>

#include <SoftwareSerial.h>
SoftwareSerial mySerial(2, 3); // RX, TX


//初期化
void setup()
{

  //シリアルポートの初期化
  Serial.begin(9600);

  //ソフトウェアシリアルの初期化
  mySerial.begin(9600);

} //setup


//メインループ
void loop()
{

  int  l; //距離
  unsigned char b = 200;

  //読み込み
  mySerial.print("S");delay(5); //トリガーを投げる
  while( mySerial.available() ){
    //Serial.println( mySerial.available() );//debug
    b = mySerial.read();//受信
    //Serial.println( b );//debug
  }//while  
  if( b <= 0   ) b=0;
  if( b >= 200 ) b=200;

  //レンジ圧縮 140までは、mm 140からは、cm
  if( b <= 139 ) {
    l = b + 60;
  } else {
    l = ((int)(b - 140 + 20)) * 10;
  }

  Serial.print("800,");

  Serial.print( l ); //UNO

  Serial.print(",0");
  Serial.println(" ");

  delay(500); // 0.5秒の待ち

} //loop