Detailed description of GET_TEMP_SPECIAL(3A)

OUT

07	11	3A	GRP	ID	ID TO	CRC

IN

13	10	4A	GRP	ID	ID TO	CRC	Sensor Type	New Value	T1	T2	T3	T4	T5	T6	T7	T8	T9	CRC

NOTE

Command 3C should be used for querying sensors on indexes greater than 0.

The command 3A shall still be available for all old and new sensor types and will return information for the sensor on index 0.

Parameters:

Sensor Type	AB – Dallas temp sensor DS1821 10 – Dallas temp sensor DS18S20 28 – Dallas temp sensor DS18B20 64 – PT100 temp. 65 – PT1000 temp. 53 – SHT71
New value	Status of value 00 New 01…FF Old
T1	Depending on sensor
T2	Depending on sensor
T3	Depending on sensor
T4	Depending on sensor
T5	Depending on sensor
T6	Depending on sensor
T7	Depending on sensor
T8	Depending on sensor
T9	Depending on sensor

10 - (DS18S20) S_INX=0

T1	TEMP	Temperature high
T2	TEMP	Temperature low
T3	NA	Not in use
T4	CNT R_1	Counter remain low
T5	NA	Not in use
T6	CNT PD_1	Counter per degree low
T7	S CAL	Status of calibration FF done, 00 not calibrated.
T8	CAL0	Calibration value high
T9	CAL1	Calibration value low

28 – (DS18B20) S_INX=0

T1	TEMP	Temperature high (upper 4 bits of temperature)
T2	TEMP	Temperature low (lower 8 bits of temperature)
T3	NA	Not in use
T4	NA	Not in use
T5	NA	Not in use
T6	NA	Not in use
T7	S CAL	Status of calibration FF done, 00 not calibrated.
T8	CAL0	Calibration value high
T9	CAL1	Calibration value low

(See DS18B20 datasheet for information on temperature format)

53 – (SHT71) S_INX=0

T1	HUM	Humidity high
T2	HUM	Humidity low
T3	TEMP	Temperature high
T4	TEMP	Temperature low
T5	NA	Not in use
T6	NA	Not in use
T7	S CAL	Status of calibration FF done, 00 not calibrated.
T8	CAL0	Calibration value high
T9	CAL1	Calibration value low

53 – (SHT71) S_INX=1

T1	TEMP	Temperature high
T2	TEMP	Temperature low
T3	NA	Not in use
T4	NA	Not in use
T5	NA	Not in use
T6	NA	Not in use
T7	S CAL	Status of calibration FF done, 00 not calibrated.
T8	CAL0	Calibration value high
T9	CAL1	Calibration value low

64 or 65 - (Pt100/1000) S_INX=0

T1	ADC_HI_BYTE	Raw ADC reading high
T2	ADC_LO_BYTE	Raw ADC reading low
T3	NA	Not used
T4	NA	Not used
T5	NA	Not used
T6	NA	Not used
T7	S CAL	Status of calibration FF done, 00 not calibrated.
T8	CAL0	Calibration value high
T9	CAL1	Calibration value low

AB - (DS1821) S_INX=0

T1	TEMP	Temperature high
T2	TEMP	Temperature low
T3	CNT R_0	Counter remain high
T4	CNT R_1	Counter remain low
T5	CNT PD_0	Counter per degree high
T6	CNT PD_1	Counter per degree low
T7	S CAL	Status of calibration FF done, 00 not calibrated.
T8	CAL0	Calibration value high
T9	CAL1	Calibration value low

Remarks for type 53

1. Treat T=(temp high : temp low) and H=(hum high : hum low) as 16 bits unsigned numbers in following equations to compute correct values of temperature and humidity. Humidity=-4.0+0.0405*H-2.8*10^-6*H^2 Temperature=-39.6+0.01*T

Remarks for type 64 and 65

1. After temperature node power on the temperature sensor is detected. The 'Sensor Type' byte is set to:

0x10 - DS18S20

0x28 - DS18B20

0x64 - PT100

0x65 - PT1000

0xAB - DS1821

0xAA - no temperature sensor

0x53 – SHT 7xx

2. Raw 16 bit ADC reading is sent on T1 and T2.

ADC = 256 * ADC_HI_BYTE + ADC_LO_BYTE

Resistance can be calculated from the formula:

For 0x64 (PT100):

R = 3.576e-3 * ADC - 0.13

for 0x65 (PT1000):

R = 57.22e-3 * ADC - 0.13

Temperature can be calculated from the formula:

for 0x64 (PT100):

R = 100 * (1 + A * t + B * t^2)

for 0x65 (PT1000):

R = 1000 * (1 + A * t + B * t^2)

where

A = 3.9083e-3

B = -5.775e-7

3. The present solution accepts both PT100 and PT1000 (the amplification is changed automatically). For both sensor types the range is -200 to +300 degrees and accuracy +/- 0.5 degree

4. The accuracy may be enhanced if calibration is implemented.