ESP-WROOM-02でI2Cセンサーを使用する

ESP-WROOM-02のArduino環境で、I2Cセンサーをつないでみました。一点ハマったところがあるので備忘録を兼ねてポストします。
（10月4日追記）デフォルトのI2Cピンがあることご指摘いただき、I2Cピンをデフォルトに変更しました。

接続構成

センサーはスイッチサイエンスさんのBME280搭載 温湿度・気圧センサーモジュールです。ピン接続は以下の通り：

• Vio — 3.3V
• Vore — 3.3V
• GND — GND
• CSB — 3.3V
• SDI (SDA) — ESP-WROOM-02 IO4（10KΩでプルアップ）
• SCK (SCL) — ESP-WROOM-02 IO14 IO5（10KΩでプルアップ）
• SDO — GND

ESP-WROOM-02 (ESP8266)のデフォルトのI2Cピンアサインは、SDA: IO04, SCL: IO05でした。(@chobicanさんのご指摘）

コード

BME280のライブラリは、Embedded Adventuresのコードを使用。Arduino用のサンプルコードがほぼ無修正で動きます。ほぼと書いたのは、一箇所だけ修正が必要で、99行目のWire.beginにSDA, SCLピンをパラメーターとして指定します。今回の例では、Wire.begin(4. 14)になります。ESP-WROOM-O2 (ESP8266)のデフォルトI2Cピンを使えば、Wire.beginのピン指定は不要です。

/*

Copyright (c) 2015, Embedded Adventures
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Contact us at source [at] embeddedadventures.com
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modification, are permitted provided that the following conditions are met:

- Redistributions of source code must retain the above copyright notice,
  this list of conditions and the following disclaimer.

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  notice, this list of conditions and the following disclaimer in the
  documentation and/or other materials provided with the distribution.

- Neither the name of Embedded Adventures nor the names of its contributors
  may be used to endorse or promote products derived from this software
  without specific prior written permission.
 
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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*/

// BME280 MOD-1022 weather multi-sensor Arduino demo
// Written originally by Embedded Adventures

#include <BME280_MOD-1022.h>

#include <Wire.h>

// Arduino needs this to pring pretty numbers

void printFormattedFloat(float x, uint8_t precision) {
char buffer[10];

  dtostrf(x, 7, precision, buffer);
  Serial.print(buffer);

}


// print out the measurements

void printCompensatedMeasurements(void) {

float temp, humidity,  pressure, pressureMoreAccurate;
double tempMostAccurate, humidityMostAccurate, pressureMostAccurate;
char buffer[80];

  temp      = BME280.getTemperature();
  humidity  = BME280.getHumidity();
  pressure  = BME280.getPressure();
  
  pressureMoreAccurate = BME280.getPressureMoreAccurate();  // t_fine already calculated from getTemperaure() above
  
  tempMostAccurate     = BME280.getTemperatureMostAccurate();
  humidityMostAccurate = BME280.getHumidityMostAccurate();
  pressureMostAccurate = BME280.getPressureMostAccurate();
  Serial.println("                Good  Better    Best");
  Serial.print("Temperature  ");
  printFormattedFloat(temp, 2);
  Serial.print("         ");
  printFormattedFloat(tempMostAccurate, 2);
  Serial.println();
  
  Serial.print("Humidity     ");
  printFormattedFloat(humidity, 2);
  Serial.print("         ");
  printFormattedFloat(humidityMostAccurate, 2);
  Serial.println();

  Serial.print("Pressure     ");
  printFormattedFloat(pressure, 2);
  Serial.print(" ");
  printFormattedFloat(pressureMoreAccurate, 2);
  Serial.print(" ");
  printFormattedFloat(pressureMostAccurate, 2);
  Serial.println();
}


// setup wire and serial

void setup()
{
  Wire.begin();     // Wire.begin(sda, scl)
  pinMode(12, OUTPUT);
  Serial.begin(115200);
}

// main loop

void loop()
{

  uint8_t chipID;
  
  Serial.println();
  Serial.println();
  Serial.println("Welcome to the BME280 MOD-1022 weather multi-sensor test sketch!");
  Serial.println("Embedded Adventures (www.embeddedadventures.com)");
  chipID = BME280.readChipId();
  
  // find the chip ID out just for fun
  Serial.print("ChipID = 0x");
  Serial.println(chipID, HEX);
  
 
  // need to read the NVM compensation parameters
  BME280.readCompensationParams();
  
  // Need to turn on 1x oversampling, default is os_skipped, which means it doesn't measure anything
  BME280.writeOversamplingPressure(os1x);  // 1x over sampling (ie, just one sample)
  BME280.writeOversamplingTemperature(os1x);
  BME280.writeOversamplingHumidity(os1x);
  
  // example of a forced sample.  After taking the measurement the chip goes back to sleep
  BME280.writeMode(smForced);
  while (BME280.isMeasuring()) {
    Serial.println("Measuring...");
    delay(50);
  }
  Serial.println("Done!");
  
  // read out the data - must do this before calling the getxxxxx routines
  BME280.readMeasurements();
  Serial.print("Temp=");
  Serial.println(BME280.getTemperature());  // must get temp first
  Serial.print("Humidity=");
  Serial.println(BME280.getHumidity());
  Serial.print("Pressure=");
  Serial.println(BME280.getPressure());
  Serial.print("PressureMoreAccurate=");
  Serial.println(BME280.getPressureMoreAccurate());  // use int64 calculcations
  Serial.print("TempMostAccurate=");
  Serial.println(BME280.getTemperatureMostAccurate());  // use double calculations
  Serial.print("HumidityMostAccurate=");
  Serial.println(BME280.getHumidityMostAccurate()); // use double calculations
  Serial.print("PressureMostAccurate=");
  Serial.println(BME280.getPressureMostAccurate()); // use double calculations
  
  // Example for "indoor navigation"
  // We'll switch into normal mode for regular automatic samples
  
  BME280.writeStandbyTime(tsb_0p5ms);        // tsb = 0.5ms
  BME280.writeFilterCoefficient(fc_16);      // IIR Filter coefficient 16
  BME280.writeOversamplingPressure(os16x);    // pressure x16
  BME280.writeOversamplingTemperature(os2x);  // temperature x2
  BME280.writeOversamplingHumidity(os1x);     // humidity x1
  
  BME280.writeMode(smNormal);
   
  while (1) {
    digitalWrite(12, HIGH);
    while (BME280.isMeasuring()) {

    }
    
    // read out the data - must do this before calling the getxxxxx routines
    BME280.readMeasurements();
    printCompensatedMeasurements();
    
    delay(1000);
    Serial.println();

    digitalWrite(12, LOW);
    delay(1000);
  }
}

参考資料

• ESP-WROOM-02のArduino環境でI2C制御