I2C温度計

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温度センサーADT7410を使う

I2C温度センサADT7410を使う

使用モジュール

秋月通商ＡＤＴ７４１０使用　高精度・高分解能　Ｉ２Ｃ・１６Ｂｉｔ　温度センサモジュール

J1J2を半田付けして基板上でSCL,SDAを10kΩのプルアップ

I2Cアドレス0x48(プログラム上は1ビットシフトして0x90)

ＡＤＴ７４１０のレジスタ

Temperature Value Register (Register Address 0x00～0x01

Adress	Bit	Default Value	Type	Name	Description
0x00(MSB)	[14:8]	0000000	R	Temp	Temperature value in twos complement format
0x00(MSB)	15	0	R	Sign	Sign bit, indicates if the temperature value is negative or positive
0x01(LSB)	0	0	R	TLOW flag/LSB0	Flags a TLOW event if the configuration register, Register Address 0x03[7] = 0 (13-bit resolution). When the temperature value is below TLOW, this bit it set to 1. Contains the Least Significant Bit 0 of the 15-bit temperature value if the configuration register, Register Address 0x03[7] = 1 (16-bit resolution).
	1	0	R	THIGH flag/LSB1	Flags a THIGH event if the configuration register, Register Address 0x03[7] = 0 (13-bit resolution). When the temperature value is above THIGH, this bit it set to 1. Contains the Least Significant Bit 1 of the 15-bit temperature value if the configuration register, Register Address 0x03[7] = 1 (16-bit resolution).
	2	0	R	TCRIT flag/LSB2	Flags a TCRIT event if the configuration register, Register Address 0x03[7] = 0 (13-bit resolution). When the temperature value exceeds TCRIT, this bit it set to 1. Contains the Least Significant Bit 2 of the 15-bit temperature value if the configuration register, Register Address 0x03[7] = 1 (16-bit resolution).
	[7:3]	00000	R	Temp	Temperature value in twos complement format.

Temperature Value Register

温度値の換算(13bit)

13ビットモードの場合は、レジスタ値の下位3ビットが不要ですので、レジスタ値を3ビット右にシフトした値で計算ます。
＜正数の場合＞　　計算値＝((MSB << 8) | (LSB&0 & f8)) >> 3
＜負数の場合＞　　計算値＝((MSB << 8) | (LSB&0 & f8) - 8192) >> 3
これを小数点位置下4桁のためまで16で割ります。
温度=　計算値 / 16

Status Register (Register Address 0x02)

Bit	Default Value	Type	Name	Description
[3:0]	0000	R	Unused	Reads back 0.
4	0	R	TLOW	This bit is set to 1 when the temperature goes below the TLOW temperature limit. The bit clears to 0 when the status register is read and/or when the temperature measured goes back above the limit set in the setpoint TLOW + THYST registers.
5	0	R	THIGH	This bit is set to 1 when the temperature goes above the THIGH temperature limit. The bit clears to 0 when the status register is read and/or when the temperature measured goes back below the limit set in the setpoint THIGH − THYST registers.
6	0	R	TCRIT	This bit is set to 1 when the temperature goes above the TCRIT temperature limit. This bit clears to 0 when the status register is read and/or when the temperature measured goes back below the limit set in the setpoint TCRIT − THYST registers.
7	1	R	RDY	This bit goes low when the temperature conversion result is written into the temperature value register. It is reset to 1 when the temperature value register is read. In one-shot and 1 SPS modes, this bit is reset after a write to the one-shot bits.

Configuration Register (Register Address 0x03)

Bit	Default Value	Type	Name	Description
[1:0]	00	R/W	Fault queue	These two bits set the number of undertemperature/overtemperature faults that can occur before setting the INT and CT pins. This helps to avoid false triggering due to temperature noise. 00 = 1 fault (default). 01 = 2 faults. 10 = 3 faults. 11 = 4 faults.
2	0	R/W	CT pin polarity	This bit selects the output polarity of the CT pin. 0 = active low. 1 = active high.
3	0	R/W	INT pin polarity	This bit selects the output polarity of the INT pin. 0 = active low. 1 = active high.
4	0	R/W	INT/CT mode	This bit selects between comparator mode and interrupt mode. 0 = interrupt mode 1 = comparator mode
[6:5]	00	R/W	Operation mode	These two bits set the operational mode for the ADT7410. 00 = continuous conversion (default). When one conversion is finished, the ADT7410 starts another. 01 = one shot. Conversion time is typically 240 ms. 10 = 1 SPS mode. Conversion time is typically 60 ms. This operational mode reduces the average current consumption. 11 = shutdown. All circuitry except interface circuitry is powered down.
7	0	R/W	Resolution	This bit sets up the resolution of the ADC when converting. 0 = 13-bit resolution. Sign bit + 12 bits gives a temperature resolution of 0.0625°C. 1 = 16-bit resolution. Sign bit + 15 bits gives a temperature resolution of 0.0078°C.

プログラム

レジスタ書込

I2C.wite(I2Cアドレス, (char[]){レジスタアドレス, レジスタ値}, 2);

レジスタ読込

I2C.wite(I2Cアドレス, (char[]){レジスタアドレス}, 1);
char data[length];
I2C.read(I2Cアドレス, data, length);

プログラム例

#include "mbed.h"

I2C myi2c(dp5, dp27);   // I2Cピン
DigitalOut myled(LED1); // LED
int addr = 0x90;        // I2Cアドレス(0x48)

// 設定
void SetConfig(char val){
    myi2c.write(addr,(char[]){0x03,val},2);
}

// 設定取得
char GetConfig(){
    myi2c.write(addr,(char[]){0x03},1,true);
  
    char read[1];
    myi2c.read(addr,read,1);
    return read[0];
}

// 温度取得
float GetTemp(){
    myi2c.write(addr,(char[]){0x00},1,true);
   
    char read[2];
    myi2c.read(addr,read,2);
   
    int value = (((read[0] & 0x7f) << 8 ) + (read[1] & 0xf8)) >> 3;
    if(read[0] & 0x80)
        value -= 8192;
   
    return value / 16.0f;    
}

int main() {
    myi2c.frequency(400000); 
    while(1) {
        myled = !myled;
        wait(0.2);
        printf("%f\n", GetTemp());
    }
}

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