T6700 Series CO2 Sensor Module Application Note
Contents
1. Calibration errors can be cleared by running the calibration procedure again with successful results l N l N l N l N 0080H IN I C N N N l 1 1 l 1 1 1 XX1 X1 1 For calibration conditions a 1 indicates that the calibration cycle is currently in progress No other calibration cycle can start while one is currently in progress and will result in an error being reported by the Modbus response to the new calibration request lf the Warm up bit is set the sensor is in a mode where internal registers are being initialized and gas ppm data is not necessarily correct APPLICATION NOTE Se TEL IRE APPLICATION NOTE FOR T67XX SERIES ee 1 2014 CO2 SENSOR REV 2 OZ OoOO PAGE 18 OF 30 9 3 GAS PPM This command reports the current gas measurement in ppm Use the Modbus Read Input Registers function 4 and read one 1 register at address 5003 D 138B H Modbus Request UART Slave Address default is 21 Function code Starting address MSB Starting Address LSB Input registers to read MSB Input registers to read LSB CRC LSB Slave Address default is 21 Function code Byte count MSB of the 16 bit data LSB of the 16 bit data CRC LSB XX CRC MSB Example 5 Modbus request response to read the GAS PPM register UART Modbus Request CH Master Transmitter Slave Receiver Function code Starting address MSB Starting Address LSB Input registers2. Europe Middle East and Asia Address Amphenol Advanced Sensors Crown Industrial Estate Priorswood Road Taunton TA2 8QY United Kingdom Telephone 44 1823 335 200 APPLICATION NOTE o P APPLICATION NOTE FOR T67XX SERIES BATEYUE 1 2014 i CO2 SENSOR REV 2 PAGE 30 OF 30 www telaire com Am phenol www amphenol sensors com Advanced Sensors 920 2013 Amphenol Advanced Sensors All Rights Reserved Specifications are subject to change without notice Amphenol Advanced Sensors is a registered trademark of Ampheno Corporation Other company or product names mentioned in this document may be trademarks or registered trademarks of their respective companies which are not affiliated with Amphenol
3. Modbus Response I C Function code Output address MSB Output Address LSB Output value MSB Output value LSB Example 13 Modbus request response to stop Single Point Calibration I C Note The UART Modbus request response is not shown APPLICATION NOTE ee TEL IRE APPLICATION NOTE FOR T67XX SERIES ee 1 2014 CO2 SENSOR REV2 OZ OoOO PAGE 24 OF 30 9 6 CHANGE SLAVE ADDRESS It is possible to change the Modbus slave address The change will only take effect after the sensor has been reset e g over the Modbus interface or power cycled The change does not take effect immediately User the Modbus Write Single Register function 6 and write the new address to the register at address 4005 D OFA5 H This example changes the current slave address to 16 D 10 H Modbus Request UART Slave Address default is 21 Function code Register address MSB Register Address LSB Register value MSB MSB will always be zero Register value LSB LSB should be between 1 247 CRC LSB Slave Address default is 21 Function code Register address MSB Register Address LSB Register value MSB Register value LSB CRC LSB Example 14 Changing the default Slave Address UART Modbus Request I C Function code Register address MSB Register Address LSB Register value MSB MSB will always be zero Register value LSB LSB should be between 1 247 APPLICATION NOTE
4. 4 and read one 1 register at address 5002 D 138A H Modbus Request UART Slave Address default is 21 Function code Starting address MSB Starting Address LSB Input registers to read MSB Input registers to read LSB CRC LSB CRC MSB Slave address Function code Byte count Status MSB Status LSB Example 3 Modbus request response to read the STATUS register UART Modbus Request CH Master Transmitter Slave Receiver Function code Starting address MSB Starting Address LSB Input registers to read MSB APPLICATION NOTE ee TEL IRE APPLICATION NOTE FOR T67XX SERIES ee 1 2014 CO2 SENSOR REV 2 OZ O PAGE 17 OF 30 Modbus Response Cl Master Receiver Slave Transmitter Function code Byte count Status MSB Status LSB Example 4 Modbus request response to read the STATUS register I C The STATUS register is a bit vector where each bit represents the status of some function within the sensor Not all bits are assigned 20000000 0000001 1 000TH 1 Error condition 2000000x WO0 xX 0002H Flasherror 20000000 0000x 0004H Calibration error XXXXXXXX XXXX XXX 0008H_ NA_ XXXXXXXX XXX XXXX_ 0010H NA XXXXXXXX POOH 0020 H_ NA XXXXXXXX X XXXXXX 0040H TNA XXXXXXXX DOXXXXX LL Kalen XXX 0400H C S For error conditions a 1 indicates an error a 0 indicates no error Flash error is fatal i e there is no recovery
5. ee TEL IRE APPLICATION NOTE FOR T67XX SERIES ee 1 2014 CO2 SENSOR REV2 OZ OoOO PAGE 25 OF 30 Modbus Response CH Function code Register address MSB Register Address LSB Register value MSB Register value LSB Example 15 Changing the default Slave Address IC Note It is necessary to restart the sensor either by power cycling or writing FF H to the RESET register before this change will take effect 9 7 ABC LOGIC ENABLE DISABLE ABC Logic is manipulated through the Modbus interface by using the Write Single Coil function 5 Coils are viewed as basically switches relays or discrete i e single bit inputs and outputs The ABC LOGIC CONTROL coil register is 1006 D O3EE H A write of FFOO H i e ON will enable the ABC Logic and a write of 0000 H i e OFF will disable the ABC Logic function For example to enable the ABC Logic one would send the Modbus request OH 03 H EE H FFH 00 H Note that the example is shown as a simple Modbus PDU For communications over a serial port e Modbus Serial Line PDU the slave address would need to be prepended and the CRC appended Modbus Request UART Slave Address default is 21 Function code Register address MSB Register Address LSB Register value MSB Enable ABC Logic Register value LSB LSB will always be zero CRC LSB CRC MSB Modbus Response UART Slave
6. for a response The response should be 7 bytes long and in this example will fill a data structure i e char array named inBuf with the result inBuf O 0x15 slave address inBuf 1 0x04 function code inBuf 2 0x02 byte count inBuf 3 0x CO2 reading MSB inBuf 4 0x CO2 reading LSB inBuf 5 0x CRC LSB inBuf 6 0x CRC MSB The CO2 can then be calculated by inBuf 3 256 inBuf 4 The simplified code example follows Send the query string and delay for the data to come back write_uart1 void MOD_READ 8 delay 50 look for a well formed response oo NOTE APPLICATION NOTE FOR T67XX SERIES mere DATE JUL 1 2014 i CO2 SENSOR PREV 2 oN oe if there are 7 bytes in the input buffer read_uart1 void inBuf 7 do a sanity check check function code and byte count if inBuf 1 0x04 amp amp inBuf 2 0x02 calculate the CO2 measurement raw_co2 measurement int inBuf 3 lt lt 8 inBuf 4 else appropriate error response else we didn t get the response we wanted appropriate error response oo NOTE APPLICATION NOTE FOR T67XX SERIES EE DATE JUL1 2014 i CO2 SENSOR PREV 2 en 11 CUSTOMER SUPPORT DETAILS North and South America Address Amphenol Advanced Sensors 967 Windfall Rd St Mary s PA 15857 Telephone 1 814 834 9140
7. of air at 400 ppm CO2 Sensor will maintain accuracy specifications with ABC Logic enabled given that it is at least four times in 21 days exposed to the reference value and this reference value is the lowest concentration to which the sensor is exposed ABC Logic requires continuous operation of the sensor for periods of at least 24 hours Note Applies when used in typical residential ambient air Consult Telaire if other gases or corrosive agents are part of the application environment 6 2 ENVIRONMENTAL Operating Temperature 50 F to 122 F 10 C to 50 C 0 to 95 RH non condensing Storage Temperature 22 F to 158 F 30 C to 70 C 6 3 ABSOLUTE MAXIMUM RATINGS In order to avoid damage to the sensor the following parameters should never be exceeded at any time during operation Min V Max V Supply Voltage V pin 3 Ground V pin 4 0 3 TX SDA RX SCL pin 1 2 MD DIR PWM pin 5 UART I2C Select pin 6 6 4 POWER ON SEQUENCE The sensor is capable of responding to commands after power on but operational accuracy of sensor won t happen until 120 sec have elapsed The sensor will reach full accuracy warm up after 10 min of operation 6 5 POWER SUPPLY REQUIREMENTS Supply Voltage 4 5 5 5VDC Average Current 20mA Peak Current 155mA APPLICATION NOTE WENN APPLICATION NOTE FOR T67XX SERIES PATE YUL 1 2014 i CO2 SENSOR RA PAGE 10 OF 30 Based on typical values at a no
8. only within power supply and electrical input and output limits as specified by the datasheet and application guide Improper use of the product may result in product damage and property loss and or personal injury 8 2 SAFETY WHILE IN USE Before installing handling using or servicing this product please consult the data sheet and application notes The product shall be used only within power supply and electrical input and output limits as specified by the datasheet and application guide Improper use of the product may result in product damage and property loss and or personal injury In use of the product the customer has sole responsibility for designing and implementing a solution which will ensure APPLICATION NOTE Po TEL IRE APPLICATION NOTE FOR T67XX SERIES ee 1 2014 CO2 SENSOR REV 2 OZ OoOO PAGE 13 OF 30 safe operation including review of appropriate reliability or required redundancy mitigation of failure modes and or meeting appropriate standards The customer is responsible for review of any special conditions for use including but not limited to environmental conditions electrical supply residual risk etc The sensor is designed for benign environments The performance and reliability may be negatively affected in environments that contain corrosive or caustic gases including but not limited to Ammonia Chlorine NOx and Ozone 8 3 MATERIAL CONTENTS ROHS and REACH declaration of conformity are available u
9. the sensor can be found on the website Please refer to the spec sheets found at www telaire com for the latest specifications 5 INSTALLATION MOUNTING 5 1 DESIGN CONSIDERATIONS To maximize the performance of T67xx module it is important to plan an appropriate location for the sensor at the design stage Airflow and proper exposure to ambient air must be secured for T67xx module to ensure optimal performance Inadequate airflow will deteriorate the response time of the sensor Also avoid excess heat The sensor is designed for benign environments The performance and reliability may be negatively affected in environments that contain corrosive or caustic gases including but not limited to Ammonia Chlorine NOx and Ozone Care must be taken to ensure that the sensor is not exposed to these compounds under any operating condition 5 2 INSTALLATION The T67xx module is a sensitive electronics assembly so effort should be made to minimize exposure to excess heat from any type of soldering operation Excess exposure to heat from installation is known to create small shift in calibration of the sensor Although the ABC Logic algorithm will correct these minor fluctuations within the first 24 hours of operation the user should minimize overexposure to heat when soldering to negate unexpected operation after installation Typically an expose of not more than 10 sec using a soldering iron set to 750 F 400 C will minimize the influence of hea
10. to read MSB Input registers to read LSB Modbus Response Cl Master Receiver Slave Transmitter Function code Byte count MSB of the 16 bit data LSB of the 16 bit data Example 6 Modbus request response to read the GAS PPM register IC APPLICATION NOTE ee TEL IRE APPLICATION NOTE FOR T67XX SERIES ee 1 2014 CO2 SENSOR REV2 OZ O OOo PAGE 19 OF 30 To calculate the gas ppm do the following ppm MSB 256 LSB For example if the Modbus UART response was Slave Address default is 21 Function code Byte count MSB of the 16 bit data LSB of the 16 bit data CRC LSB CRC MSB Example 7 Calculating GAS ppm Then the gas could be calculated as 1 256 159 415 Where OTH 1 D and 9F H 159 D APPLICATION NOTE Se TEL IRE APPLICATION NOTE FOR T67XX SERIES ee 1 2014 CO2 SENSOR REV 2 OZ O O o PAGE 20 OF 30 9 4 RESET DEVICE The sensor can be reset though this is not normally recommended over the Modbus interface The reset is immediate and there is no response The sensor will act as if the power was cycled Use the Modbus Write Single Coil function 5 and write OOFF H to the register at address 1000 D 03E8 H to reset the sensor Modbus Request UART Slave Address default is 21 Function code Output address MSB Output Address LSB Output value MSB Output value LSB XX CRC LSB XX CRC MSB Example 8 Modbus reque
11. 3 g GOMMA MA EE 13 91 PIRMWARE REVISION ME 14 Ja FATU E E AE E e eee eee 16 Io 1209 od E 18 94 RESET RE 20 9 5 START SINGLE POINT CAUIBRATION 21 96 GRANGE SLAVE RR 24 97 ABCLOGIC ENABLES DISABLE E 25 10 ENS 5 OS a T 27 11 Ee SUD OOM RT ar e cies tan ee gece tins ewes cease ties A 29 APPLICATION NOTE ee APPLICATION NOTE FOR T67XX SERIES BATE YUL 1 2014 CO2 SENSOR KELA PAGE 4 OF 30 1 PREAMBLE The purpose of this document is to outline the required interface design and communication protocol for the T67xx CO2 Sensor The intended audience is any developer who wishes to query the sensor for information utilizing either the C PWM or UART interfaces 2 INTERFACE CONNECTOR The six pin through hole connector on the PCB is were power and IO for the sensor are located see Figure 1 below A six pin 0 1 header must be installed in order to connect the sensor to a controller There are several different I O configurations that are supported by the sensor and are determined by the voltage that is measured on pin 6 of the connector at startup 1 TX SDA H 2 RX SCL 3 V 4 GND PWM 5 6 CTRL TEST Figure 1 T67XX Interface Connector Note Precautions should be taken to observe specified limits and prevent damage from electrostatic discharge or rough handling Please refer to ANSI ESD S20 20 1999 for more information on preventing ESD damage and IPC 610 Rev D for more information on proper e
12. Address default is 21 Function code Register address MSB APPLICATION NOTE ee e APPLICATION NOTE FOR T67XX SERIES LTE ZIL 72077 i CO2 SENSOR REV 2 PAGE 26 OF 30 Register Address LSB Register value MSB Register value LSB CRC LSB CRC MSB Example 16 Enable ABC Logic UART Modbus Request UC Function code Register address MSB Register Address LSB Register value MSB Disable ABC Logic Register value LSB LSB will always be zero Example 17 Disable ABC Logic I C APPLICATION NOTE el APPLICATION NOTE FOR T67XX SERIES PATESUL 1 2014 i CO2 SENSOR nee PAGE 27 OF 30 10 EXAMPLE CODE Reading Value for CO Reading the T67xx sensor in an embedded design is fairly easy This example assumes that the controlling micro processor has already initialized a UART and the sensor has the default settings from the factory eg the slave address is 0x15 Because the slave address and CRC will never change the programmer can just defined the entire Modbus request as constants in as array For example static const uint8_ t MOD _READJ 0x15 slave address 0x04 Modbus function Read Input Registers 0x13 Starting Address 5003 MSB first Ox8B 0x00 of registers to read 1 MSB first 0x01 0x46 CRC LSB then MSB 0x70 The following example sends the above character array out the serial port and then delays 50ms before looking
13. OTE FOR T67XX SERIES mere DATE JUL 1 2014 i CO2 SENSOR REV 2 i O Een 1004 m emm em gt gt 0 PPM Ed EH 4ms 4ms Lg Lg 4 PPM er oe AmS Ee e 8 PPM o __ 100Oms eee 1996 PPM 1002m8 ems yi 2000 PPM 1004 mis es Figure 6 Example of the PWM for 2K model APPLICATION NOTE WENN APPLICATION NOTE FOR T67XX SERIES PATE YUL 1 2014 i CO2 SENSOR RA PAGE 12 OF 30 Potential circuit design to convert 25 kHz PWM to an analog output for I O configuration 2 IFC PWM at 25 kHz OPTIONAL_ 3 0_TO_SV C1 a D Lut OPTIONAL_1K 5K PWM ANALOG OUT Figure 7 Potential Circuit Design for 25 kHz PWM output to Analog Signal Conversion The 25 kHz PWM can be filtered to create an analog output Above is one filtering circuit where R3 and R4 will set the gain of the amplifier 8 SAFETY 8 1 DISCLAIMER Telaire makes no warranty representation or guarantee regarding the suitability of this product for any particular application including safety critical applications Nor does Telaire assume any liability arising out of the application or use in any product or circuit Telaire specifically disclaims all liability without limitation consequential or incidental damages No statuary or fitness for particular purpose shall be implied WARNING Before installing the product review the product data sheet and this application guide The product shall be used
14. SB Output value LSB CRC LSB EC CRC MSB Example 10 Modbus request response to start Single Point Calibration UART Modbus Request I C Function code Output address MSB Output Address LSB Output value MSB Output value LSB APPLICATION NOTE ee TEL IRE APPLICATION NOTE FOR T67XX SERIES ee 1 2014 CO2 SENSOR REV2 OZ O PAGE 22 OF 30 Modbus Response CH Function code Output address MSB Output Address LSB Output value MSB Output value LSB Example 11 Modbus request response to start Single Point Calibration I C Calibration takes several minutes The status of the single point can be determined by reading the status register The calibration command cannot be restarted but can be stopped as detailed in the following example Modbus Request UART Slave Address default is 21 Function code Output address MSB Output Address LSB Output value MSB Output value LSB CRC LSB Slave Address default is 21 Function code Output address MSB Output Address LSB Output value MSB Output value LSB CRC LSB CRC MSB Example 12 Modbus request response to stop Single Point Calibration UART APPLICATION NOTE ee TEL IRE APPLICATION NOTE FOR T67XX SERIES ee 1 2014 CO2 SENSOR REV2 OZ O PAGE 23 OF 30 Modbus Request I C Function code Output address MSB Output Address LSB Output value MSB Output value LSB
15. TELAIRE 167xx C0 Sensor Module Application Note APPLICATION NOTE Po TEL IRE APPLICATION NOTE FOR T67XX SERIES a 1 2014 CO2 SENSOR REV 2 OZ O OO PAGE 2 OF 30 REVISION RECORD REVISION ORIGINATOR RELEASED 1 Norman Hannotte Feb 19 2014 Description of changes Initial Document release REVISION ORIGINATOR RELEASED 2 Norman Hannotte July 1 2014 Description of changes Correction to I2C pin out Added example code customer support sections Add details of ABC Logic on off Added detail to installation mounting section Addition of Operation details safety conversion of PWM to analog signal sections Remove watermark and preliminary markings APPLICATION NOTE Po TEL IRE APPLICATION NOTE FOR T67XX SERIES a 1 2014 CO2 SENSOR REV 2 OZ O O PAGE 3 OF 30 Table of Contents TS une E E leis ere N eno EEE PEENE EE VE EE E SAE A E AN 4 SEET 4 3 Communication Modbus Protocol 7 CAWET NEE e E ree ee ee eer 7 CEET 7 EE UE 8 HUSTON e UNO BE 8 5 1 Design considerations A 8 2 MPV AO Nese cg cerereedctaccetyt es sn E AEN 8 59 ESD POCA ONS EE 8 6 ADE FAC MCSA EE 9 SCH DN ABO Bo 0 e 9 SC IOP E EE 9 6 3 Absol te IMU aN E 9 64 E en Ee ne 9 6 5 Power Supply Requirements n0nnnnennnnennrennnntnnesnrrsrnrestrrrrnrrsrrrrsnrrnrnrrsrrrrnnrrserrrnneene 9 6 6 Evaluation Demonstration his 10 TP OT Eet E 10 E EE 12 Sh SCLIN CN EE 12 o2 OO Wie U O eea 12 AUS e E e E E antanddnqameatynadatinue 1
16. egisters to read MSB Number of registers to read LSB CRC LSB CRC MSB Modbus Response UART Slave address Function code Byte count Status MSB Status LSB CRC LSB CRC MSB Example 1 Modbus request response to read the firmware revision UART APPLICATION NOTE Po TEL IRE APPLICATION NOTE FOR T67XX SERIES ee 1 2014 CO2 SENSOR REV2 OZ O OOo PAGE 15 OF 30 CC all bytes in hexadecimal The default I C slave address is 21 D 15 H and not shown Modbus Request Master Transmitter Slave Receiver Function Code Starting Address MSB Starting Address LSB Number of registers to read MSB Number of registers to read LSB Modbus Response Master Receiver Slave Transmitter Function code Byte count status MSB xX status LSB Example 2 Modbus request response to read the firmware revision IC lt is important to note that the sensor is a slave device only The user must implement a master DC device to facilitate reading and writing to the sensor APPLICATION NOTE Se TEL IRE APPLICATION NOTE FOR T67XX SERIES ee 1 2014 CO2 SENSOR REV 2 OZ O OOo PAGE 16 OF 30 9 2 STATUS This command returns a register with the status of various functions on the sensor The user must verify that no error condition exists in the sensor Also user must verify that the sensor has completed the warm up stage Use the Modbus Read Input Registers function
17. ents an TC interface The default conditions are e The sensor only acts as a slave device e C 7 bit addressing is used The default slave address is 21 0x15 e TC 100kbit s Standard Mode Note There is an internal pull up resistor on pin 1 of the I C interface Customer will need to provide an external pull up resistor on pin 2 with a recommended value of 4 7k TC interface can operate at both 3 3V and 5V logic levels 3 Pin 6 is pulled to ground by a resistor between 10kQ and 100kQ Table 3 I O Pin Configuration 3 Pin Description OO UART TX output from sensor UART Rx input to sensor Becomes a test input for Telaire and should be left unconnected by the user 6 Becomes an output pin used to drive an RS485 transceiver APPLICATION NOTE Po TEL IRE APPLICATION NOTE FOR T67XX SERIES ee 1 2014 CO2 SENSOR REV 2 o Z Oo OO o PAGE 7 OF 30 T67xx CO Sensor UART TX UART RX e pINSN C RS485 DATA DIRECTION 10 kO TO 100 kO Figure 4 Simplified Schematic I O Configuration 3 The condition described by 3 above is useful if the sensor is used in an RS485 dropped node network configuration This network would be supplied by the user In this condition pin 6 becomes the RS 485 transceiver data direction logic 3 COMMUNICATION MODBUS PROTOCOL The T67xx sensor uses the Modbus protocol for all communications The documents are freely available on the Modbus WEB site at http www m
18. lectronic assembly practices In addition to this the sensor does not have internal reverse polarity protection Care should be taken to connect the sensor to the controller in the correct wiring configuration to avoid damage 1 Pin 6 is left unconnected by the user and will therefore be left floating It will be pulled up by an internal 1MQ resistor In this condition Table 1 UO Pin Configuration 1 Pin Description O UART TX output from sensor UART Rx input to sensor PWM output at approximately 1Hz APPLICATION NOTE Po TEL IRE APPLICATION NOTE FOR T67XX SERIES ee 1 2014 CO2 SENSOR REV2 OZ OoOO O PAGE 5 OF 30 T67xx CO Sensor 1 UART TX UART RX PWM AT 1Hz PIN 6 N C Figure 2 Simplified Schematic I O configuration 1 In this condition the sensor implements a RS 232 serial interface The default serial conditions are e 19200 Baud e 1 START bit e 8 DATA bits e 1 EVEN PARITY bit e 1 STOP bit 2 Pin 6 is grounded by the user In this condition Table 2 I O Pin Configuration 2 C SDA Serial Data Line ine Pin i DC SCL Serial Clock Line PWM output at approximately 25kHz APPLICATION NOTE Le APPLICATION NOTE FOR T67XX SERIES ZATE YUE 20713 i CO2 SENSOR PREV 2 _ PAGE 6 OF 30 T67xx CQ Sensor 1 I2C SDA 2 12C SCL 5 PWM AT 25KHz 6 PIN 6 GROUNDED Figure 3 Simplified Schematic I O configuration 2 In this condition the sensor implem
19. minal 5VDC input 6 6 EVALUATION DEMONSTRATION KITS Evaluation kits are available in order to help customers develop their application The kit includes a sample of the sensor cable and software that will enable the user to better understand the performance of the sensor in their intended design Please contact Telaire for further details or visit the website at www telaire com 7 PWM OUTPUTS The T67xx sensor has a selectable Pulse Width Modulation PWM output feature on Pind based on the state of Pin 6 during power on The two types of supported PWM operate at 1Hz PWM and 25k Hz and are proportional to the range of the sensor as determined by the model For example if the model is a 16713 5k the units PWM output will be proportional to a 0 to 5000 ppm output range For PN 16713 the unit will have an output proportional to a 0 2000 ppm measurement A 4 7K pull up resistor to a voltage reference can be added if desired The slow 1Hz PWM output option allows the user to measure the duration of the pulse and correlate this to a CO measurements Start End 1004 ms high gt ow E gt gt 2 ms lt gt Figure 5 Details of 1Hz PWM In order to convert the pulse to a reading in PPM the user should use the following equation PPM tyutse 2 2 for 0 2000 ppm models PPM tpuise 2 5 for 0 5000 ppm models Where tpuise Measured value of pulse PPM Measured CO Value ooo NOTE APPLICATION N
20. odbus org specs php 3 1 UART RS232 RS485 For UART communications reference the recommendations found in the document Modbus Serial Line Protocol and Implementation Guide V1 02 This document includes detailed information on how to calculate the required CRC Cyclical Redundancy Checking bytes lt is important to note that for Modbus over serial lines i e RS 232 and RS 485 the user MUST INCLUDE THE CYCLICAL REDUNDANCY CHECK CRC fields at the end of the Modbus request The CRC calculation is not necessary for communications over the TC interface 3 2 C The DC implementation does not use the Serial Line protocol The sensor does use the Modbus protocol and wraps the message in 12C format Please reference to the TC specification and users manual at the following URL for details on IC communication www nxp com documents user_manual UM10204 pdf APPLICATION NOTE Po TEL IRE APPLICATION NOTE FOR T67XX SERIES ee 1 2014 CO2 SENSOR REV 2 OZ O OO PAGE 8 OF 30 The sensor always operates as a slave In the examples below the implementer using the I C interface will need communicate with the sensor as either a master transmitter for Modbus requests or a master receiver for Modbus responses The sensor will not initiate communications i e it will not become a master and respond to the request It is up to the master to read the response from the sensor 4 SPECIFICATION All information about the performance of
21. pon request Please contact customer service for more details 9 COMMAND SUMMARY The following commands can be sent to the sensor Table 4 Modbus Command Summary Modbus Register SE FIRMWARE FIRMWARE_REVISION ot 5001D uintt6 t Returns the firmware revision 1389 H from the sensor Returns a status register from the STATUS dech 5002 D uint16 t sensor Additional details are 138A H below Input 5003 D GAS PPM RO 138B H uinti6 t The current gas ppm calculation Coils 1000 D Reset the sensor over the PEDE Ee wo open Hp Modbus network SLABE RS KS Go GE uinti6 t Start a single point calibration a 4005 D Change of sensor address ee OFA5 H default address is 21 D 15 H TM SES RE an cis ce Enable or disable ABC Logic Where RO is Read Only WO is Write Only and RW is Read or Write There are examples given in the sections below APPLICATION NOTE Po TEL IRE APPLICATION NOTE FOR T67XX SERIES ee 1 2014 CO2 SENSOR REV2 OZ ooo PAGE 14 OF 30 9 1 FIRMWARE REVISION This command will return the current firmware revision of the sensor The user is required to append the CRC for each of the command over UART Use the Modbus Read Input Registers function 4 and read one 1 register at address 5001 D 1389 H Example UART all bytes in hexadecimal Modbus Request UART Slave address Function Code Starting Address MSB Starting Address LSB Number of r
22. st to reset the sensor UART Modbus Request CH Master Transmitter Slave Receiver Function code Output address MSB Output Address LSB Output value MSB Output value LSB Example 9 Modbus request to reset the sensor I C Note There is no response The sensor resets immediately APPLICATION NOTE Po TEL IRE APPLICATION NOTE FOR T67XX SERIES ee 1 2014 CO2 SENSOR REV 2 OZ O Oo PAGE 21 OF 30 9 5 START SINGLE POINT CALIBRATION This command starts the single point calibration routine The single point calibration routine is usually done at ambient conditions 500ppm 25 C and takes several minutes to complete after being started 6 minutes The sensor can be queried during this time for status and current gas ppm readings The user can check on the status of the calibration by reading the status register and noting if the single point calibration bit is set The calibration can be stopped before completing See examples Use the Modbus Write Single Coil function 5 and write OOFF H to the register at address 1004 D O3EC H to start the calibration Write O000 H during calibration to stop the calibration function Modbus Request UART Slave Address default is 21 Function code Output address MSB Output Address LSB Output value MSB Output value LSB CRC LSB Slave Address default is 21 Function code Output address MSB Output Address LSB Output value M
23. t on the measurement of the T67xx module The use of low temperature solder is also recommended lt is recommended to handle the sensor by the edges of the PCBA Any stress applied to the PCB or the gold OBA assembly can cause mechanical stress that will create temporary shift in the calibration of the sensor Although he ABC Logic algorithm will correct for these shifts in the first 24 hours of operation extra care in handling will minimize the risk of variations that can be seen out of the box 5 3 ESD PRECAUTIONS Precautions should be taken to observe specified limits and prevent damage from electrostatic discharge or rough handling Please refer to ANSI ESD S20 20 1999 for more information on preventing ESD damage for more information on proper electronic assembly practices APPLICATION NOTE Po TEL IRE APPLICATION NOTE FOR T67XX SERIES ee 1 2014 CO2 SENSOR REV 2 O Z OoOO PAGE 9 OF 30 6 OPERATION DETAILS 6 1 ABC LOGIC Automatic Background Logic or ABC Logic is a patented self calibration technique that is designed to be used in applications where concentrations will drop to outside ambient conditions 400 ppm at least three times in a 7 days typically during unoccupied periods Full accuracy to be achieved utilizing ABC Logic With ABC Logic enabled the sensor will typically reach its operational accuracy after 24 hours of continuous operation at a condition that it was exposed to ambient reference levels
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