RTD. Temperature Circuit EZO TM. Features. PT100 / PT1000 temperature probe circuit V 1.2

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1 RTD PT100 / PT1000 temperature probe circuit Features Reads Extreme sensing range from C to 1254 C Accurate temperature readings down to the thousandths place Accuracy ±(0.10 C * T) Automatically detects if probe is PT100 or PT1000 Temperature output in Celsius, Kelvin or Fahrenheit On-board data logger storing up to 50 individual temperature readings Optional single point calibration Single reading or continuous reading modes Data format is ASCII V 1.2 This is an evolving document check back for updates. Two data protocols UART asynchronous serial connectivity (RX/TX voltage swing 0-VCC) I 2 C (default I 2 C address 0x66) Compatible with any microprocessor that supports UART, or I2c protocol Operating voltage: 3.3V to 5V Reads temperature from any off-the-shelf PT100 or PT1000 temperature probe Description PT100 and PT1000 temperature probes are used in many different applications and are considered the standard temperature probe for industrial process systems. They offer low cost temperature sensing over a wide temperature range. The fast response time and precise readings makes PT100 or PT1000 temperature probes a great fit for any embedded application. Unfortunately, they cannot be easily connected to a microcontroller. The EZO RTD Temperature Circuit has been designed to offer a simple solution to bridge the gap between microcontroller and temperature probe. When connected to a AA class RTD temperature probe Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 1

2 A Temperature Circuit

3 . Contents Circuit identification... System overview... Power consumption... Pin out... Device operation... Wiring diagram... Calibration theory... On board data logger... Board mounting... Calibration UART Mode... Calibration I2C Mode Temperature Circuit UART Mode UART command quick reference... L... C... R... Cal... S... D... M... Name... I... Response... Status... Sleep... Serial... Factory... I2C... Manual switching to I2C mode... Plock I 2 C Mode I 2 C mode... Data from a read back event... I 2 C timing... I 2 C command quick reference... L... R... Cal... D... M... I... Status... I2C Address change... Sleep... Serial... Factory... Manual switching to UART mode.. Plock... Circuit dimensions... Circuit footprint... Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved

4 UART Mode I 2 C Mode Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 4

5 System overview The Atlas Scientific EZO RTD Temperature circuit is a small footprint computer system that is specifically designed to be used in robotic applications where the embedded systems engineer requires accurate and precise measurements of temperature through a generic PT100/PT1000 temperature probe. An RTD is a Resistance Temperature Detector. In 1871 Sir William Siemens proposed that the best material to use for a RTD was platinum. This is because it has a very stable resistance to temperature relationship over a large range. (1871? That guy must have had a wooden multimeter). Today RTDs are very popular in industrial applications. The most common type of RTD is made out of platinum. The two types of platinum RTDs that are commonplace today are the PT100 and PT1000 RTD. The PT stands for platinum and the 100 or 1000 represents the resistance at 0 C. Because an RTD is a type of resistor they have tolerances similar to that of a resistor. For example, a 4.7KΩ resistor commonly comes in tolerances of 10%, 5% or 1%. A platinum RTD comes in 4 common tolerances class AA, class A, class B, and class C. Accuracy table Class AA A B C Accuracy ±(0.10 C * T) ±(0.15 C * T) ±(0.3 C * T) ±(0.6 C * T) Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 5

6 Power consumption LED MAX STANDBY SLEEP 5V ON OFF 16 ma 15.4 ma 15.3 ma 15 ma 3.00 ma ON 14.3 ma 13.8 ma 3.3V OFF 14 ma 13.6 ma 1.46 ma Absolute maximum ratings * Parameter MIN TYP MAX Storage temperature (EZO RTD) -65 C 125 C Operational temperature (EZO RTD) -40 C 25 C 85 C VCC 3.3V 5V 5.5V *Note: Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to maximum rating conditions for extended periods may affect device reliability Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 6

7 Pin Out GND Vcc TX / SDA Return for the DC power supply Operates on 3.3V 5.5V All EZO class circuits can operate in either UART mode, or I 2 C mode The default state is UART mode. In UART mode, this pin acts as the transmit (TX) line. The default baud rate is 9600, 8 bits, no parity, no flow control, one stop bit. If standard RS232 voltage levels are desired, connect an RS232 converter such as a MAX232. If the devices is in I 2 C mode, this pin acts as the Serial Data Line (SDA). The I 2 C protocol requires an external pull up resistor on the SDA line (resistor not included). RX / SCL All EZO class circuits can operate in either UART mode, or I 2 C mode. The default state is UART mode. In UART mode, this pin acts as the receive (RX) line. If the devices is in I 2 C mode, this pin acts as the Serial Clock Line (SCL). The I 2 C protocol requires an external pull up resistor on the SCL line (resistor not included). PRB/ PGND These pins are to be connected to a PT100 or PT1000 temperature probe. It makes no difference which lead of the temperature probe is connected to the two probe pins. Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 7

8 Device operation When an EZO class circuit is first powered up the boot sequence will begin. This is indicated by the LED moving from Red to Green to Blue. The boot up sequence takes 1 second. Once the device has booted up the circuit will output: *RS<CR> *RE<CR> Indicating the device is ready for operation. The LED will enter its default blink pattern (see page 9) indicating the device is operational and actively taking readings. Default state Mode UART Baud rate 9600 bps 8 data bits 1 stop bit no parity no flow control Reading time 1 reading every second Probe type PT100 or PT1000 RTD Data output Temperature Units C ( F or K) Data Type Floating point LEDs: Enabled Steady Green = Power on / standby Red double blink = Command received and not understood Green double blink per data packet = Continuous data streaming Cyan = taking a reading Format String Encoding ASCII characters followed by a carriage return <CR> Maximum string length: 14 characters If the response code is enabled the EZO class circuit will respond *OK<CR> after a command is acknowledged. If an unknown command is sent the RDT Circuit will respond *ER<CR> this will happen whether or not response codes are enabled. Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 8

9 Default LED blink pattern Temperature Circuit This is the LED pattern for Continous Mode (which is the default state) Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 9

10 Wiring diagram To connect the Circuit to your microcontroller, follow the diagram below. Make sure your Circuit and microcontroller share a common ground. TX on your Circuit connects to RX on your microcontroller. If in I 2 C mode connect SDA to SDA and SCL to SCL *4.7k pull up resistor on SDA and SCL may be required Temperature Circuit The Atlas Scientific EZO class Temperature circuit is highly sensitive equipment. Debugging should be done in a bread board; Not like what is show in this photo. Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 10

11 Calibration theory PT100 and PT1000 temperature probes have very predicable behavior at varying temperatures. This is why they make such good temperature probes. Because of this fact, calibration is not required. However for the user who feels that calibration is necessary single point calibration is available. Calibration can be done at any value. For best results calibrating at the boiling point of water is recommended. Elevation and Boiling Point table Use purified/distilled water Meters Celsius To calibrate against the freezing point of water; one method would be to put the probe in an ice bath of distilled water. If further calibration accuracy is required a dry block temperature calibrator should be used. Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 11

12 On board data logger The Atlas Scientific EZO RTD Temperature circuit comes equipped with an on board data logger capable of storing 50 temperature readings. Each memory location is numbered, the first reading is stored in memory location 1 and the last reading is stored in memory location 50. Temperature readings that are stored to the data logger will be retained even if the power is cut. The onboard data logger can be programmed to store readings at an interval as small as once every 10 seconds and as large as once every 320,000 seconds (3.7 days). The onboard data logger stores the readings in a circular buffer beginning at memory location 1. If the memory buffer becomes full the data logger will write over memory location 1 with the newest reading. Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 12

13 Board mounting The Atlas Scientific EZO RTD Temperature Circuit should be tested in a bread board with different colored jumper wires connecting to each pin of the EZO RTD Temperature Circuit. The EZO RTD Temperature Circuit should not have wires for other devices in your system laying on top of it. If long term use is desired a PCB should be made to hold the device. Perfboards (sometimes called Protoboards) should never be used. Micro-shorts and bleeding voltages are very common when using such boards. Achieving stable reading can be quite difficult or impossible. Using perfboards (sometimes called Protoboards) will void your devices warranty. No support will be given. Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 13

14 UART Mode TM Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 14

15 UART mode command quick reference There are a total of 16 different commands that can be given to the EZO RTD Temperature circuit. All commands are ASCII strings or single ASCII characters Command Function Default state C Cal D Factory I I2C L M Name Plock R Response S Serial Sleep Status Enable / Disable or Query continuous readings (pg.17) Performs calibration (pg.19) Enable / Disable data logger (pg.21) Factory reset (pg.29) Device information (pg.24) Sets the I 2 C ID number (pg.30) Enable / Disable or Query the LEDs (pg.16) Memory Recall / Clear (pg.22) Set or Query the name of the device (pg.24) Enables / Disables the protocol lock feature (pg.32) Returns a single reading (pg.18) Enable / Disable or Query response code (pg.25) Temperature scale (pg.20) Set the baud rate (pg.28) Enter low power sleep mode (pg.27) Retrieve status information (pg.26) Enabled User must calibrate Disabled N/A N/A Not set LEDs Enabled N/A Not set Disabled N/A Enabled N/A 9600 N/A N/A Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 15

16 <CR> represents a carriage return (ASCII 13). The user does not transmit the literal string <CR>. Commands are not case sensitive. LED control All EZO class circuits have a tri-color LED, used to indicate device operation. UART mode LED color definitions: Steady Green = Power on/ standby Red double blink = Command received and not understood Green blink = Data transmission sent Cyan = taking a reading L,1<CR> LED enable L,0<CR> LED disable L,?<CR> Query the LED Device response L,1 <CR> (If the response code is enabled, the EZO class circuit will respond *OK<CR> ) The Led will be enabled and the green power on/ standby LED will turn on L,0 <CR> (If the response code is enabled, the EZO class circuit will respond *OK<CR> ) The Led will be disabled L,? <CR> (If the response code is enabled, the EZO class circuit will respond *OK<CR> )?L,1<CR> if the LED is enabled?l,0<cr> if the LED is disabled Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 16

17 <CR> represents a carriage return (ASCII 13). The user does not transmit the literal string <CR>. Commands are not case sensitive. Continuous reading mode All EZO class circuits are capable of continuous mode operation. In continuous mode, the device will output its readings, one after the other continuously until the continuous mode disable command has been issued. All EZO class circuits are defaulted to operate in continuous mode. If the LEDs are enabled, each time a data transmission occurs, the green LED will blink. C,1<CR> Continuous mode enable C,0<CR> Continuous mode disable C,?<CR> Query continuous mode Device response C,1 <CR> (If the response code is enabled, the EZO class circuit will respond *OK<CR> ) The EZO class RTD circuit will output a string containing a temperature reading once per Second C <CR> (1 second) C <CR> (2 seconds) C <CR> (n* seconds) C,0 <CR> (If the response code is enabled, the EZO class circuit will respond *OK<CR> ) Continuous data transmission will cease. C,? <CR> (If the response code is enabled, the EZO class circuit will respond *OK<CR> )?C,1<CR> if continuous mode is enabled.?c,0<cr> if continuous mode is disabled. Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 17

18 <CR> represents a carriage return (ASCII 13). The user does not transmit the literal string <CR>. Commands are not case sensitive. Single reading mode All EZO class circuits are capable of taking a single reading upon request. If the LEDs are enabled, each time a data transmission occurs, the green LED will blink. R<CR> Returns a single reading Device response (If the response code is enabled, the EZO class circuit will respond *OK<CR> ) The EZO class RTD circuit will output a single string containing a temperature reading 1 second after the command was issued. C <CR> (1 second) Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 18

19 <CR> represents a carriage return (ASCII 13). The user does not transmit the literal string <CR>. Commands are not case sensitive. Calibration The EZO class RTD circuit can be calibrated using single point calibration. Cal,n<CR> Where n is any temperature. Cal,clear<CR> Cal,? <CR> Clears all calibration data Query the calibration Device response Cal,clear<CR> (If the response code is enabled the EZO class circuit will respond *OK<CR> ) There is no other output associated output with this command. Cal,n<CR> (If the response code is enabled the EZO class circuit will respond *OK<CR> ) The LED we turn cyan during the calibration. Cal,? (If the response code is enabled the EZO class circuit will respond *OK<CR> ) If not calibrated?cal,0 If calibrated?cal,1 Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 19

20 <CR> represents a carriage return (ASCII 13). The user does not transmit the literal string <CR>. Commands are not case sensitive. Temperature scale The Atlas Scientific EZO RTD Temperature Circuit is capable of outputting its temperature readings in 3 deferent scales, Celsius, Fahrenheit and Kelvin. By default the temperature output is in Celsius. S,C<CR> This command will set the EZO RTD Circuit to output its reading in Celsius. S,F<CR> S,K<CR> S,?<CR> This command will set the EZO RTD Circuit to output its reading in Fahrenheit. This command will set the EZO RTD Circuit to output its reading in Kelvin. Queries the scale of the output temperature. Device response S,C<CR> (If the response code is enabled the EZO class circuit will respond *OK<CR> ) There is no other output associated output with this command. S,F<CR> (If the response code is enabled the EZO class circuit will respond *OK<CR> ) There is no other output associated output with this command. S,K<CR> (If the response code is enabled the EZO class circuit will respond *OK<CR> ) There is no other output associated output with this command. S,?<CR> (If the response code is enabled the EZO class circuit will respond *OK<CR> )?S,C<CR> Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 20

21 <CR> represents a carriage return (ASCII 13). The user does not transmit the literal string <CR>. Commands are not case sensitive. Enable / disable data logger Enabling the onboard data logger will start a countdown timer from the time period entered. When the timer has counted down a temperature reading will be stored in the data logger. The time period is in 10 second intervals and can be any value from 1 to D,n<CR> Where n is any number from 1 to The value entered represents the number of seconds counted until a readings is stored. D,0<CR> D,?<CR> Sending the D,0 command will disable the data logger Queries the state of the data logger Example D,1<CR> Store a reading to the data logger every 10 seconds D,2<CR> Store a reading to the data logger every 20 seconds D,234<CR> Store a reading to the data logger every 2340 seconds Device response D,n<CR> (If the response code is enabled the EZO RTD circuit will respond *OK<CR> ) Once a reading has been stored the RTD circuit will output * indicating that the reading has been logged *<CR> (A reading has been stored to the data logger) Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 21

22 <CR> represents a carriage return (ASCII 13). The user does not transmit the literal string <CR>. Commands are not case sensitive. Memory recall Up to 50 readings can be stored to the onboard data logger. The temperature readings stored to the onboard data logger can be recalled by two different methods; CVS method and single step method. Comma Separated Value (CSV) method M,ALL<CR> Example 23.52,23.74,23.35,23.45,23.01<CR> Oldest Newest Single step method Each time the command is issued the next value stored in the memory will be output. M<CR> Example 1,23.52<CR> 2:23.74<CR> 3:23.35<CR> M<CR> Recall the stored data using the single step method. M,ALL<CR> Recall the stored data in CSV format. M,?<CR> Show what memory location has last been written to. The scale of the temperature data stored in the data logger is not fixed. Using the S,C S,F and S,K commands will change the way the temperature data is read back. Setting the scale to Fahrenheit will cause the memory output to be in Fahrenheit. Setting the scale to Kelvin will cause the memory to output the exact same data in Kelvin. Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 22

23 <CR> represents a carriage return (ASCII 13). The user does not transmit the literal string <CR>. Commands are not case sensitive. Memory clear To clear all the stored temperature readings the memory clear command must be issued. Deletion of the data stored in the data logger is permanent and cannot be undone. M,CLEAR<CR> Issuing this command will clear all stored memory. Device response (If the response code is enabled, the EZO class circuit will respond *OK<CR> ) *CLR<CR> Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 23

24 <CR> represents a carriage return (ASCII 13). The user does not transmit the literal string <CR>. Commands are not case sensitive. Device identification All EZO class circuits are capable of being assigned a name. This is a simple way to identify the device in a system that consists of multiple EZO class circuits. A name can consist of any combination of ASCII characters, with a length of 1 to 16 characters long, no blank spaces. NAME,nnn<CR> Sets the device name, where nnn is the given name. NAME,?<CR> Query the device name Device response NAME,DEVICE_1<CR> (If the response code is enabled, the EZO class circuit will respond *OK<CR> ) There is no other output associated output with this command. NAME,?<CR> (If the response code is enabled, the EZO class circuit will respond *OK<CR> )?NAME, DEVICE_1<CR> Device information The EZO class circuit can identify itself by device type and firmware version. This is done by transmitting the I command. I<CR> Device information Device response?i,rtd,1.0<cr> (If the response code is enabled, the EZO class circuit will respond *OK<CR> ) Where RTD = device type 1.0 = firmware version number Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 24

25 <CR> represents a carriage return (ASCII 13). The user does not transmit the literal string <CR>. Commands are not case sensitive. Response codes The Atlas Scientific EZO class circuits, have 7 response codes to help the user understand how the device is operating, and to aid in the construction of a state machine to control the EZO class circuit. All EZO class devices indicate a response code has been triggered, by transmitting a string with the prefix * and ending with a carriage return <CR>. A list of response codes *ER *OV *UV *RS *RE *SL *WA An unknown command has been sent The circuit is being ovearvolted (VCC>=5.5V) The circuit is being undervolted (VCC<=3.1V) The circuit has reset The circuit has completed boot up The circuit has been put to sleep The circuit has woken up from sleep Only the response code *OK can be disabled. Disabling this response code is done using the response command. RESPONSE,1<CR> RESPONSE,0<CR> RESPONSE,?<CR> Enable response code (default) Disable response code Query the response code Device response RESPONSE,1<CR> EZO class circuit will respond *OK<CR> RESPONSE,0<CR> There is no response to this command RESPONSE,?<CR>?RESPONSE,1<CR> If the response code is enabled?response,0<cr> If the response code is disabled Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 25

26 <CR> represents a carriage return (ASCII 13). The user does not transmit the literal string <CR>. Commands are not case sensitive. Reading the status of the device The Atlas Scientific EZO class circuit, is able to report its voltage at the VCC pin and reason the device was last restarted. Restart codes P S B W U power on reset software reset brown out reset watchdog reset unknown STATUS<CR> Device response (If the response code is enabled, the EZO class circuit will respond *OK<CR> )?STATUS,P,5.038<CR> Where: P is the reason for the last reset event Where: is the its voltage at the VCC Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 26

27 <CR> represents a carriage return (ASCII 13). The user does not transmit the literal string <CR>. Commands are not case sensitive. Low power state To conserve energy in between readings, the Atlas Scientific EZO class circuit, can be put into a low power sleep state. This will turn off the LEDs and shut down almost all of the internal workings of the EZO class circuit. The power consumption will be reduced to 3.00 ma at 5V and 1.46 ma at 3.3V. To wake the EZO class circuit, send it any character. SLEEP<CR> Enter low power sleep state Device response (If the response code is enabled, the EZO class circuit will respond *OK<CR> ) *SL<CR> Device response to wake up: *WA<CR> Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 27

28 <CR> represents a carriage return (ASCII 13). The user does not transmit the literal string <CR>. Commands are not case sensitive. Change baud rate The Atlas Scientific EZO class circuit, has 8 possible baud rates it can operate at. The default baud rate is 9600 bps 8 data bits 1 stop bit no parity no flow control Baud rate changes will be retained even if power is cut. Data bits, stop bits, parity and flow control are fixed and cannot be changed bps bps bps bps bps bps bps bps (Using an example baud rate of 38400) SERIAL,38400<CR> Device response (If the response code is enabled, the EZO class circuit will respond *OK<CR> ) The EZO class circuit will respond with a Purple LED double blink. The EZO class circuit will then restart at the new baud rate. The LED blink will happen even if the LEDs are disabled. Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 28

29 <CR> represents a carriage return (ASCII 13). The user does not transmit the literal string <CR>. Commands are not case sensitive. Factory reset All EZO class circuits, are capable of resetting themselves to the original factory settings. Issuing a factory reset will: Reset the calibration back to factory default Set debugging LED to on Enable response codes This command will not change the set baud rate. Factory<CR> Factory reset Device response (If the response code is enabled, the EZO class circuit will respond *OK<CR> ) The EZO class circuit, will respond: *RE<CR> Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 29

30 <CR> represents a carriage return (ASCII 13). The user does not transmit the literal string <CR>. Commands are not case sensitive. Switch from UART mode to I 2 C mode Transmitting the command I 2 C,[n] will set the EZO class circuit into I 2 C mode from UART mode. Where [n] represents any number from The I 2 C address is sent in decimal ASCII form. Do not send the address in hexadecimal ASCII form. (Using as example an I 2 C ID number of 100) I2C,100<CR> Device response If an address > 127 is given *ER Indicating an error has occurred If an address >0 and <128 is given (If the response code is enabled, the EZO class circuit will respond *OK<CR> ) *RS<CR> The device will restart in I 2 C mode The Green LED used to indicate that the device is powered and awaiting an instruction will now change to Blue. Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 30

31 <CR> represents a carriage return (ASCII 13). The user does not transmit the literal string <CR>. Commands are not case sensitive. Manual switching to I 2 C mode All EZO class circuits can be manually switched from UART mode, to I 2 C mode. If this is done the EZO class RTD Temperature circuit, will set its I 2 C address to 102 (0x66). 1. Cut the power to the device 2. Disconnect any jumper wires going from TX and RX to the master micro controller 3. Short the PRB pin to the TX pin 4. Power the device 5. Wait for LED to change from Green to Blue 6. Remove the short from the probe pin to the TX pin 7. Power cycle the device 8. The device is now I 2 C mode Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 31

32 <CR> represents a carriage return (ASCII 13). The user does not transmit the literal string <CR>. Commands are not case sensitive. Protocol lock When the protocol lock feature is enabled all changes to the communication protocol are blocked. This means that whatever communication mode the device is in (I 2 C or UART); that communication protocol cannot be changed by any means. Furthermore, changes to the devices baud rate or I 2 C address also cannot be changed. By default the protocol lock is: DISABLED Changes to this setting are retained even if the power is cut. PLOCK,1<CR> PLOCK,0<CR> PLOCK,?<CR> Enables the protocol lock feature Disables the protocol lock feature Query the state of the lock Device response PLOCK,1<CR> (If the response code is enabled, the EZO class circuit will respond *OK<CR> ) There is no other output associated output with this command. PLOCK,0<CR> (If the response code is enabled, the EZO class circuit will respond *OK<CR> ) There is no other output associated output with this command. PLOCK,?<CR> (If the response code is enabled, the EZO class circuit will respond *OK<CR> )?PLOCK,1<CR> if the lock in enabled?plock,0<cr> if the lock in disabled Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 32

33 <CR> represents a carriage return (ASCII 13). The user does not transmit the literal string <CR>. Commands are not case sensitive. Once the protocol lock is enable the following commands / actions will no longer work Manual switching to I 2 C or UART mode Software switching from I 2 C or UART mode UART baud rate change I 2 C address change If the protocol lock is enabled attempting to manually switch to UART or I 2 C mode will have no effect. If any of the software commands are issued to switch mode, baud rate or I 2 C address the EZO class device will return *ER<CR> Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 33

34 I 2 C Mode TM Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 34

35 I 2 C mode An I 2 C address can be any number from If the EZO Class ph circuit was put into I 2 C mode by jumping PRB to TX, the I 2 C address is 102 (0x66). Temperature Circuit Once an EZO class device has been put into I 2 C mode the Green power LED that was used in UART mode will now switch to a Blue LED. This indicates the device is now in I 2 C mode. The I 2 C protocol is considerably more complex than the UART (RS-232) protocol. Atlas Scientific assumes the embedded systems engineer understands this protocol. Communication to the EZO class device is controlled by the master. The EZO class device as an I 2 C slave. The slave device is not able to initiate any data transmissions. An I 2 C write event is defined as such In order to get the response from device, it is necessary to initiate a read command. The I 2 C protocol does not permit the slave device to initiate any data transmissions. An I 2 C read event is defined as such Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 35

36 Data from a read back event Temperature Circuit The first byte of the data read back, is the response code. This byte informs the master of the status of the data about to be read back. For all commands, the first byte of the read data is the response code, which is defined as Value Meaning No Data there is no pending request, so there is no data to return from the circuit Pending the request is still being processed. Ensure that you have waited the minimum time to guarantee a response Failed the request failed Success the requested information is ready for transmission. There may be more bytes following this which are returned data The bytes transmitted after that, will be the requested data. When all the data has been transmitted each additional byte will be a NULL. Example A read request when no command has been given. Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 36

37 All I 2 C mode responses are in ASCII format however, they do not terminate with a <CR> rather, they terminate with a NULL. The Null termination makes data manipulation easier once it has been received. Example EZO class device responds to a request for a reading float =byte[7] Byte[0]= 1 (decimal 1) byte[1]= 1 (ASCII 49) byte[2]= 2 (ASCII 50) byte[3]=. (ASCII 46) byte[4]= 3 (ASCII 51) byte[5]= 4 (ASCII 52) byte[6]= NULL (ASCII 0) I 2 C timing When a command is issued to the EZO class device, a certain amount of time must be allowed to pass before the data is ready to be read. Each command specifies the delay needed before the data can be read back. EZO class devices do not support I 2 C clock stretching. All commands are sent to the EZO class device in the same ASCII format as in UART mode however, there is no <CR> sent at the end of the transmission. Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 37

38 I 2 C command quick reference Temperature Circuit There are a total of 12 different commands that can be given to the EZO RTD Temperature circuit. Command Cal D Factory I I2C L M Plock R Serial Sleep Status Function Performs calibration (pg.41) Enable / Disable data logger (pg.42) Factory reset (pg.50) Device information (pg.45) Change I 2 C address (pg.47) Enable / Disable or Query the LEDs (pg.39) Memory Recall / Clear (pg.43) Enables / Disables the protocol lock feature (pg.52) Returns a single reading (pg.40) Switch back to UART mode (pg.49) Enter low power sleep mode (pg.48) Retrieve status information (pg.46) Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 38

39 I 2 C LED control All EZO class circuits have a tri-color LED used to indicate device operation. I 2 C mode LED color definitions: Steady Blue = Power on/ standby Red double blink = Command received and not understood Blue blink = Data transmission sent Green = taking a reading Temperature Circuit L,1 LED enable L,0 LED disable L,? Query the LED Device response L,1 The Led will be enabled and the blue power on/ standby LED turn on. After 300ms, an I 2 C read command can be issued to get the response code. A decimal 1 would indicate the command has been successfully processed. L,0 The Led will be disabled After 300ms, an I 2 C read command can be issued to get the response code. A decimal 1 would indicate the command has been successfully processed. L,? After 300ms, an I 2 C read command can be issued to get the response code. (?L,1) if the LED is enabled (?L,0) if the LED is disabled Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 39

40 I 2 C take reading When a reading is taken, the LED (if enabled) will turn Green, indicating that a reading is being taken. Once the reading has been taken, the LED will turn back to Blue. R Returns a single reading Time until instruction is processed: 600ms Temperature Circuit Device response After 600ms, an I 2 C read command can be issued to get the response: The TEMP parameter represents many bytes. The string will be no longer than 9 bytes. Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 40

41 I 2 C Calibration The EZO class RTD circuit can be calibrated using single point calibration. Cal,n Where n is any temperature Cal,clear Clears all calibration data Cal,? Query the calibration Device response Cal,n<CR> The LED will during Green during the calibration. After 1 second, an I2C read command can be issued to get the response code. A decimal 1 would indicate the command has been successfully processed. Temperature Circuit Cal,clear<CR> The LED will blink during the calibration clearing process. After 300ms, an I2C read command can be issued to get the response code. A decimal 1 would indicate the command has been successfully processed. Cal,? The LED will blink during the calibration clearing process. After 300ms, an I2C read command can be issued to get the response code. If not calibrated (?CAL,0) If calibrated (?CAL,1) Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 41

42 I 2 C Enable / disable data logger Temperature Circuit Enabling the on-board data logger will start a countdown timer from the time period entered. When the timer has counted down a temperature reading will be stored in the data logger. The time period is in 10 second intervals and can be any value from 1 to D,n D,0 D,? Where n is any number from 1 to The value entered represents the number of seconds counted until a readings is stored. Sending the D,0 command will disable the data logger Queries the state of the data logger Example D,1 Store a reading to the data logger every 10 seconds D,2 Store a reading to the data logger every 20 seconds D,234 Store a reading to the data logger every 2340 seconds Device response The LED will move from Blue to Green and then back to blue again each time a reading is logged. In I 2 C mode the EZO-RTD circuit it is not able to transmit a signal indicating that the data has been logged. This is due to the nature of the I 2 C protocol although; the M command can be used to see how many readings have been logged (see page 41). Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 42

43 I 2 C Memory Recall Temperature Circuit Up to 50 readings can be stored to the onboard data logger. The temperature readings stored to the onboard data logger can be recalled one reading at a time. Data logging must be disabled before issuing a memory recall command. The EZO-RTD circuit cannot recall the data in memory while it is still logging data. You must issue the command D,0 to disable data logging before recalling logged data. Each time the command is issued the next value stored in the memory will be output. M Recall the stored data one location at a time M,? Show what memory location has last been written to. After 300ms an I 2 C read command can be issued to get the stored data. Example I2C_write(M) 300ms I2C_READ I2C_write(M) 300ms I2C_READ Data is retrieved from oldest to newest ,23.74,23.35,23.45,23.01 Oldest Newest The scale of the temperature data stored in the data logger is not fixed. Using the S,C S,F and S,K commands will change the way the temperature data is read back. Setting the scale to Fahrenheit will cause the memory output to be in Fahrenheit. Setting the scale to Kelvin will cause the memory to output the exact same data in Kelvin. Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 43

44 I 2 C Memory Clear Temperature Circuit To clear all the stored temperature readings the memory clear command must be issued. Deletion of the data stored in the data logger is permanent and cannot be undone. M,CLEAR Issuing this command will clear all stored memory. After 300ms an I2C read command can be issued to get the response code. A decimal 1 would indicate the command has been successfully processed. Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 44

45 I 2 C Device Info The EZO class circuit, can identify itself by device type and firmware version. This is done by transmitting the I command. I Device information Time until instruction is processed 300 ms Temperature Circuit Device response: After 300ms, an I 2 C read command can be issued to get the response:?i,rtd,1.0 Where RTD = device type 1.0 = firmware version number Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 45

46 Reading the status of the device in I 2 C mode The Atlas Scientific EZO class circuit, is able to report its voltage at the VCC pin and the reason the device was last restarted. Restart codes P power on reset S software reset B brown out reset W watchdog reset U unknown STATUS Time until instruction is processed, 300ms Device response After 300ms, an I 2 C read command can be issued, to get the response Temperature Circuit?STATUS,P,5.038 Where: P is the reason for the last reset event Where: is the its voltage at the VCC Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 46

47 I 2 C Address change Transmitting the command I 2 C,[n] while the EZO class circuit is already in I 2 C mode will change the devices I 2 C address. Where [n] represents any number from Warning! After changing the I 2 C address the EZO class circuit will no longer be able respond to any commands from the master device until its code has been updated with the new I 2 C address I2c,[n] Device response If an address >0 and <128 is given If an address of 0 or and address of > 127 is given EZO class circuit will issue an error response and not change the I 2 C address. The blue led used to indicate the device is in I 2 C mode will turn purple then the device will restart using its new I 2 C address. No calibration information will be lost by changing the I 2 C address Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 47

48 I 2 C Low power state Temperature Circuit To conserve energy in between readings, the Atlas Scientific EZO class circuit can be put into a low power sleep state. This will turn off the LEDs and shut down almost all of the internal workings of the EZO class circuit. The power consumption will be reduced to 3.00mA at 5V and 1.46mA at 3.3V. To wake the EZO class circuit send it any command. SLEEP Enter low power sleep state Time until instruction is processed, 300ms Device response If the LEDs are enabled, the Blue LED will blink and then turn off. There is no other output associated with this command. Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 48

49 Switch from I 2 C mode to UART mode Transmitting the command serial,<n> will set the EZO class circuit into UART mode from I 2 C mode. Where [n] represents any of one the 8 available baud rates. (Using as example a baud rate of 9600) SERIAL,9600 Device response If an incorrect baud rate is sent the device will not switch into UART mode and the Red LED will flash. If a correct baud rate is given: The Blue LED used to indicate that the device is powered and awaiting an instruction will now change to Green. Incorrect Correct Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 49

50 Factory reset Temperature Circuit All EZO class circuits, are capable of resetting themselves to the original factory settings. Issuing a factory reset will: Reset the calibration back to factory default Reset default temperature to 25 C Set debugging LED to on. Enable response codes This command will not change the set I 2 C address Factory Factory reset Device response After 300ms the STATUS command can be issued to see that the device was reset.?status,s,5.038 Where: S is the reason for the last reset event (software reset) Where: is the its voltage at the VCC Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 50

51 Manual switching to UART mode All EZO class circuits, can be manually switched from I 2 C mode to UART mode. If this is done, the EZO class ph circuit, will set its baud rate to Cut the power to the device 2. Disconnect any jumper wires going from TX and RX to the master micro controller 3. Short the PRB pin to the TX pin 4. Power the device 5. Wait for LED to change from Blue to Green 6. Remove the short from the probe pin to the TX pin 7. Power cycle the device 8. The device is now UART mode Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 51

52 Protocol lock When the protocol lock feature is enabled all changes to the communication protocol are blocked. This means that whatever communication mode the device is in (I 2 C or UART); that communication protocol cannot be changed by any means. Furthermore, changes to the devices baud rate or I 2 C address also cannot be changed. By default the protocol lock is: DISABLED Changes to this setting are retained even if the power is cut. PLOCK,1 Enables the protocol lock feature PLOCK,0 Disables the protocol lock feature PLOCK,? Query the state of the lock Device response PLOCK,1 After 300ms, an I 2 C read command can be issued to get the response code. A decimal 1 would indicate the command has been successfully processed. PLOCK,0 After 300ms, an I 2 C read command can be issued to get the response code. A decimal 1 would indicate the command has been successfully processed. PLOCK,? After 300ms, an I 2 C read command can be issued to get the response code. If locked (?PLOCK,1) Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 52

53 If unlocked (?PLOCK,0) Once the protocol lock is enable the following commands / actions will no longer work Manual switching to I 2 C or UART mode Software switching from I 2 C or UART mode UART baud rate change I 2 C address change If the protocol lock is enabled attempting to manually switch to UART or I 2 C mode will have no effect. If any of the software commands are issued to switch mode, baud rate or I 2 C address the EZO class device will return: Indicating that the request failed. Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 53

54 Circuit dimensions Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 54

55 How to make a footprint for the Atlas Scientific TM RTD circuit 1. In your CAD software place an 8 position header. 2. Place a 3 position header at both top and bottom of the 8 position header as shown. 3. Once this is done, you can delete the 8 position header. Make sure that the two 3 position headers are 17.78mm (0.7 ) apart from each other. Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 55

56 TM Atlas-Scientific.com Copyright Atlas Scientific LLC All Rights Reserved 56