QMC5883Lでとりあえず3軸地磁気データを取得する で一応動作確認はできたが、実際問題どのように制御すればよいのか全くわからない。 今回はその謎の解決を図るべく、ステータス・レジスタの実験を行った。
参考:
7.2 Measurement Example
- Check status register 06H[0] ,
1means ready.- Read data register 00H - 05H
9.2.2 Status Register
There are two status registers located in address 06H and 0CH. Register 06H has three bits indicating for status flags, the rest are reserved for factory use. The status registers are read only bits.
Addr. 7 6 5 4 3 2 1 0 06H — — — — — DOR OVL DRDY Data Ready Register (DRDY), it is set when all threeaxis data is ready, and loaded to the output data registers in the continuous measurement mode. It is resetto
0by reading any data register ( 00H - 05H ) through I2C commends
- DRDY
0- no new data
1- new data is ready
Overflow flag(OVL) is set to
1if any data of three axis magnetic sensor channels is out of range. The output data of each axis saturates at -32768 and 32767, if any of the axis exceeds this range, OVL flag is set to1. This flag is reset to0if next measurement goes back to the range of (-32768, 32767), otherwise, it keeps as1.
- OVL
0- normal
1- data overflow
Data Skip (DOR) bit is set to
1if all the channels of output data registers are skipped in reading in the continuous-measurement mode. It is reset to1by reading any data register ( 00H - 05H ) through I2C
- DOR
0- normal
1- data skipped for read
データを読む際に status register で新しいデータが存在しているか確認してから読むように Example には書かれている。 その status register に関しては3つのフラグが存在しているらしい。
ということらしいぞ、というのが以下のソースコードを実行して判明した。 文章だけではいまいちよくわからない・・・。
#include <Wire.h>
#include <string>
#include <sstream>
#include <iomanip>
const uint8_t ADDRESS = 0x0d;
const uint8_t X = 0x00;
const uint8_t Y = 0x02;
const uint8_t Z = 0x04;
typedef struct{
byte msb;
byte lsb;
} DATA;
std :: ostream& operator<< (std :: ostream& out, const uint8_t value);
inline const byte readData (const uint8_t _address, const uint8_t _register, DATA& _data);
inline void printData(const std :: string& _prefix, const DATA& _data);
// status register data
byte stat = 0;
void setup() {
Wire.begin();
Serial.begin(115200);
while( ! Serial);
Serial.println("QML5883L raw compass data");
uint8_t err;
Wire.beginTransmission(ADDRESS);
Wire.write(0x0b);
Wire.write(0x01);
err = Wire.endTransmission();
if(err){
Serial.print("error Set/Reset period FBR : ");
Serial.println(err);
}
Wire.beginTransmission(ADDRESS);
Wire.write(0x09);
Wire.write(0x1d);
err = Wire.endTransmission();
if(err){
Serial.print("error set continuous measurement mode");
Serial.println(err);
}
stat = 0;
}
void loop() {
DATA x, y, z;
byte err;
std :: stringstream ss;
//read status register
Wire.beginTransmission(ADDRESS);
Wire.write(0x06);
err = Wire.endTransmission(false);
if(err){
ss << "error : 0x" << std :: setfill('0') << std :: setw(2) << std :: hex << ADDRESS;
ss << ":0x" << std :: setfill('0') << std :: setw(2) << std :: hex << 0x06;
ss << " -> " << err;
Serial.println( ss.str().c_str() );
ss.str("");
return;
}
Wire.requestFrom(ADDRESS, static_cast<uint8_t>(1));
stat = Wire.read();
Wire.endTransmission();
Serial.print ("status = ");
Serial.println(stat);
if( ! (stat & 0x07) ){
Serial.println("Data is not ready");
return;
}
if( stat & 0x04 ){
Serial.println("Data skipped");
}
if( stat & 0x01 ){
Serial.println("Data Ready");
}
err = readData(ADDRESS, X, x);
if(err){
ss << "X error : " << err;
Serial.println( ss.str().c_str() );
ss.str("");
}
err = readData(ADDRESS, Y, y);
if(err){
ss << "Y error : " << err;
Serial.println( ss.str().c_str() );
ss.str("");
}
err = readData(ADDRESS, Z, z);
if(err){
ss << "Z error : " << err;
Serial.println( ss.str().c_str() );
ss.str("");
}
// printData("X", x);
// printData("Y", y);
// printData("Z", z);
stat = 0;
}
void printData(const std :: string& _prefix, const DATA& _data){
std :: stringstream ss;
ss << _prefix << " MSB = 0x" << std :: hex << _data.msb;
Serial.println( ss.str().c_str() );
ss.str("");
ss << _prefix << " LSB = 0x" << std :: hex << _data.lsb;
Serial.println( ss.str().c_str() );
ss.str("");
}
const byte readData(const uint8_t _address, const uint8_t _register, DATA& _data){
byte err;
std :: stringstream ss;
//X LSB
Wire.beginTransmission(_address);
Wire.write(_register);
err = Wire.endTransmission(false);
if(err){
ss << "error : 0x" << std :: setfill('0') << std :: setw(2) << std :: hex << _address;
ss << ":0x" << std :: setfill('0') << std :: setw(2) << std :: hex << _register;
ss << " -> " << err;
Serial.println( ss.str().c_str() );
ss.str("");
return err;
}
Wire.requestFrom(_address, static_cast<uint8_t>(1));
_data.lsb = Wire.read();
Wire.endTransmission();
//X MSB
Wire.beginTransmission(_address);
Wire.write(_register + 1);
err = Wire.endTransmission(false);
if(err){
ss << "error : 0x" << std :: setfill('0') << std :: setw(2) << std :: hex << _address;
ss << ":0x" << std :: setfill('0') << std :: setw(2) << std :: hex << _register + 1;
ss << " -> " << err;
Serial.println( ss.str().c_str() );
ss.str("");
return err;
}
Wire.requestFrom(_address, static_cast<uint8_t>(1) );
_data.msb = Wire.read();
Wire.endTransmission();
return static_cast<byte>(0);
}
std :: ostream& operator<< (std :: ostream& out, const uint8_t value){
out << static_cast<int>(value);
return out;
}
出力結果
status = 1
Data Ready
status = 0
Data is not ready
status = 0
Data is not ready
status = 1
Data Ready
status = 0
Data is not ready
status = 1
Data Ready
status = 4
Data skipped
status = 0
Data is not ready
status = 1
Data Ready
status = 0
Data is not ready
status = 0
Data is not ready
status = 1
Data Ready
汚いソースだが、やっていることはシンプルで、
// status register data
byte stat = 0;
レジスタの値を取り込む変数を用意し
//read status register
Wire.beginTransmission(ADDRESS);
Wire.write(0x06);
err = Wire.endTransmission(false);
if(err){
ss << "error : 0x" << std :: setfill('0') << std :: setw(2) << std :: hex << ADDRESS;
ss << ":0x" << std :: setfill('0') << std :: setw(2) << std :: hex << 0x06;
ss << " -> " << err;
Serial.println( ss.str().c_str() );
ss.str("");
return;
}
Wire.requestFrom(ADDRESS, static_cast<uint8_t>(1));
stat = Wire.read();
Wire.endTransmission();
Serial.print ("status = ");
Serial.println(stat);
レジスタのデータを取得して表示
if( ! (stat & 0x07) ){
Serial.println("Data is not ready");
return;
}
if( stat & 0x04 ){
Serial.println("Data skipped");
}
if( stat & 0x01 ){
Serial.println("Data Ready");
}
各ビットのフラグの状況に合わせたエラー処理、メッセージ出力 ということを前回のソースに追加している。