目的
I2Cのテスト
1 PWM
2 VDD
3 GND
4 シリアル出力
8 SWD
7 SWD
6 SDA
5 SCL



//I2C_Servo_V2_031_1

#include <Arduino.h>
#include <Wire.h>
#include <HardwareSerial.h>
#include <Servo.h>

Servo fs90r;  // create servo object to control a servo

int val;           // variable to read the value from the analog pin
int servopin = 16; // pin used to connect the servo

//初期化
void setup()
{

  delay(3000); //not delete

  //シリアルの初期化
  Serial.setTx(PA2_ALT1);
  Serial.setHalfDuplex();
  Serial.begin(9600);

  //i2cの初期化
  Wire.setSDA(PA12);
  Wire.setSCL(PA11);
  Wire.begin(); //pa12 pa11
  Wire.begin(0x40);  //I2Cスレーブアドレスの設定
  Wire.onReceive(receiveEvent); //データが来ると呼ばれる関数

  fs90r.attach(servopin, 900, 2100); // attaches the servo on pin 9 to the servo object
                                     // Be careful to min and max values...

} //setup


//メインループ
void loop(){
} //loop


//レシーブイベント
void receiveEvent(int howMany) {

  int x = Wire.read(); //I2C受信データの読み込み

  char c_hex[] = {
      '0', '1', '2', '3', '4', '5', '6', '7',
      '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'
  };
  
  char buf[] = { '[',c_hex[(x >> 4) & 0x0f], c_hex[x & 0x0f]  ,']', 0 };
  //
  //  char buf[] = { x, 0  };

  //I2Cスレーブの受信データの表示
  Serial.print( buf );
  //Serial.print( (char)x );

  val = map(val, 0, 256, 0, 180); // scale it to use it with the servo (value between 0 and 180, at 90,
                                   // motor is stopped)

  fs90r.write(val);                // sets the servo speed according to the scaled value

}//receiveEvent