DXA-DXI Quick Start Guide
Contents
1. Jewel QUICK START GUIDE MODEL DXA DXI 100 200 DIGITAL ACCELEROMETER amp INCLINOMETER JEWELL INSTRUMENTS LLC 50 Perimeter Road Manchester NH 03103 PHONE 800 227 5955 E MAIL sales jewellinstruments com Jewell Instruments DXA DXI Quick Start Guide v 7 2013 DXA DXI Quick Start Guide A Hardware Connections The DXA I Unit make use of a barrel style connector MS27476Y 10D35P for interface with the external systems In order to communicate with your DXA I Unit please connect the following RETURN D TX CONNECTOR MS27476Y10D35P MATES WITH MS27473T10B35S Case Ground Optional B Packet Structure amp Decodin Packet Structure Each data packet received from the unit consists of 7 bytes when either polled RS 485 or set to continuous sending mode Emulated RS 422 The quantitative data output is 18 bits long in the DO D1 D2 bytes The order and significance of these bytes is fixed and is explained the following 7 Byte Data Packet Prefix UAID D0 D1 D2 Aux Checksum Prefix The prefix byte will always start the beginning of any data packet The value of this prefix for all data packets will be OxA6 UAID The UAID byte serves as both the identifier for which axis is transmitting on a particular unit and the address for incoming commands to a unit The UAID consists of 2 parts a 6 bit BASE concatenated with a 2 bit OFFSET Only the base is user selectable The d2. mask off the Flag bits scale will be Q31 Reading will peg at these values but the instrument is specified only over its calibrated range these end values may not even be reachable The calibrated Full Scale and inclination values for a unit with 60 degree full scale reading correspond to 60 deg In the Q31 scaled integer above with 18 actual data bits 60 degrees corresponds to Ox3A980000 and 60 degrees corresponds to Ox3A980000 Ox3A980000 Ox80000000 OxBA980000 Converting these back to angle yields 60 000 degrees Reading the data as a 32 bit fixed signed integer type int or long depending on your architecture Store the bytes DO D1 D2 into Reading with D2 occupying the MSB of the data element Reading amp OxffffcO00 Mask off the Flag bits if Reading amp Ox80000000 Determine if signed Set_Negative TRUE Reading 0x80000000 Reading Reading gt gt 14 Shift for scaling in 32b if Set_Negative float Reading 1000 Reading represented as xx xxx degrees else float Reading 1000 Reading represented as xx xxx degrees Jewell Instruments DXA DXI Quick Start Guide v 7 2013 C Command Structuring Commands sent to the unit are set by a specific firmware structure which includes a static prefix unit addressing the arguments and a verification checksum In this subsection we will cover the different elements of the command structure and ident
3. a sufficient amount of times constantly in order cover the 28 mS start up window Take into account the time between break rubout execution start time and power cycle if your power supply will need to be disconnected manually we can call this system power delay For a graphical timeline representation please see below fo _ Power to System gt System Power s Delay ee ce Rubout Loop Execution a Time 2 If successful the unit will stop sending any data and appear idle If true you have successfully placed the unit into temporary RS 485 mode You can confirm this by requesting a executing a poll command If untrue the unit will continue to send data constantly and the process in step one will need to be repeated Once in temporary RS 485 mode if the unit needs to be placed into a permanent RS 485 mode the Turn RS 422 Emulation OFF command must be executed If you are just modifying parameters to then return to RS 422 mode execute the applicable commands In either situation the final parameter altering command should be followed by allow update and update configuration If you placed the unit in permanent RS 485 mode upon power cycle the unit should not be transmitting and 1s waiting for your polling 3 In order to make the transition from RS 485 operation to RS 485 operation the break command not required Instead RS 422 operations are reactivated by sending the Turn 422 Emulation ON com
4. de the 2 LSb s you would have to use a 32 bit integer If you store it left justified in the 32 bit integer and mask off the Flag bits scale will be Q31 0x00000000 is mid value Og or O degrees 0x7fffc000 and Ox80000000 represent 1g minus resolution unit at the positive end Reading will peg at these values but the instrument is specified only over its calibrated range these end values may not even be reachable poe 1 1 1 on Jewell Instruments DXA DXI Quick Start Guide v 7 2013 The data can be read as a 32 bit signed integer type int or long depending on your architecture Store the bytes DO D1 D2 into Reading with D2 occupying the MSB of the data element Reading amp OxffffcO00 Mask off the Flag and Code bits Acceleration is type float or double Acceleration g s float Reading Ox80000000ul DXI Models Value is in milli degrees sign bit and 17 incremental bits These results in the MSB representing the largest value as a standard unsigned integer of the output value where bit O of 0 17 represent 0 001 Degrees Ox 2 02E5 sign bit 1 unsigned int lol 02 E5 0 741 Available integer sizes in C are generally 8 lt lt n bits If 16 bits are enough you can store just D2 and D1 as a Q15 1 e 15 bits with a minimum resolution of 0 004 degrees value To include the 2 LSB s you would have to use a 32 bit integer If you store it left justified in the 32 bit integer and
5. efault address for a unit is X Axis 0x71 and Y Axis 0x72 The default base value is 0x 1C standalone or 0x70 when left justified in the UAID Byte D0 This is the first byte which contains output data it is also referred to as the status byte It contains the two least significant bits and the remainder 6 Jewell Instruments DXA DXI Quick Start Guide v 7 2013 bits represents the flag and code portions of the status byte The following is the binary breakout of the status byte XXX D1 This byte consists entirely of data output and it is MSB in relation to the 2 bits in DO but is placed in midpoint in the full 18 bit data output D2 This byte consists entirely of data output and it is MSB in relation to both D1 and D0 7 8 as seen below DO __I___l__ Aux The Auxiliary byte serves a variety of purposes that are dependent on the configuration parameters Functions include indicating the current DCOCTL register value number of samples in an output average etc Checksum Checksum computation for packet transmission verification Decoding DXA Models Value is in fractional g s with 17 fraction bits These results in the MSB representing the largest fractional portions of the output value where bit 16 of 0 17 represent 0 5g ji Kli n Available integer sizes in C are generally 8 lt lt n bits If 16 bits are enough you can store just D2 and D1 as a Q15 e 15 fraction bits value To inclu
6. h the poll command is sent to both axis The Set Max Avg Time input value of the function under the same name allows for an unsigned integer value between 1 and 255 to be entered This entry is used in order to convert that number back into the unsigned hexadecimal equivalent At which point it is used as the second argument for the function and the checksum is calculated for the user For more information on the implementation and calculating the effective 1 pole filter target value see the DXA DXI Manual F Operational Modes and Mode Conversion The DXA DXI have 2 dedicated operational modes and one intermediary operational mode This can be seen below in the operational mode flowchart Jewell Instruments DXA DXI Quick Start Guide v 7 2013 RS 422 RS 485 Operation Operation T Yes Is RS 422 Temporary Emulation Turned On RS 485 Operation 28 mS While in startup Window Start Up Window Yes Was the BREAK Command j Sta rt Up pa The RS 422 operational mode has been designed to continuously send a stream of data outgoing without interruption for parameter adjustment Once in this operational mode the Rx Ports on the DSP are disabled even when commands can be fit between output packets The RS 485 operational mode has been designed to provide data when polled and allow for the use of the dual purpose Tx Rx data connections to receive data into the unit This inco
7. he break command is only applied to a unit set to RS 422 mode it is included in this sub section In order to allow for the input of any commands the unit must accept a break command in order to stop transmission before the unit starts streaming data This must occur in a 28 mS window at power on In order to facilitate this process the RS 422 sub mode of the DXA DXI Demo has the break command built in for easy transition to the temporary RS 485 unit state Instruments Right click on the Y Axis of either graph and select whether the AutoScaling is turned on or off If the AutoScaling is turned off then you can double click on the end points of the scale and change them to what you want For example if the unit is an inclinometer and has a range of 30 then set the top marker for 30 and the ttom marker for 30 For a unit that is an accelerometer with a range of 1G set the top marker to 1 and the bottom marker to 1 The filter can be turned on or off and be set to different cut off frequencies or different orders The filter is external to the device X Output g s Y Output g s 0 000000 0 000000 Waveform Chart X Axis g s Plot 0 caw Waveform Chart Y Axis g s Plot 0 Ea Filter Off On low cutoff freq fl 3 0 5000 order Ep End Program Pressing the break button near the bottom of the VI window will automate sending the Break command continuously with rubouts As the user you need to cycle power during this 5 sec
8. ify each element s purpose and manipulation PREFIX In order to determine the length of a command being received by the DXA DXI unit the value of a command prefix is predetermined as seen in the following table COMMAND TYPE PREFIX COMMAND LENGTH ADDRESS This value will correspond with the UAID of the desired unit being targeted for command ARGUMENT The argument for a command can be either 0 2 bytes The only command for which an argument isn t required is the poll command where a combination of the prefix and unit address satisfies the requirements for decoding For single action commands as in turning off RS 422 emulation off or turning on averaging one argument is used In the event a command is issued where the tuning of a specific parameter is required the argument consists of one static byte to identify the primary command and the user selected value as an unsigned integer CHECKSUM In order to calculate the checksum for any command complete the Hexadecimal addition of all non checksum bytes Take the least significant nibble overflow from the addition and add it back into the sum The next step is to NOT the sum Ex Command AC 72 B1 Checksum AC 72 11E 11E Bl 1CF O1 CE First Nibble 1 Ol CF DO DO 2F Checksum Just as a note when using the BREAK command it is recommended that the command be spaced by 2 Rubout characters OxFF especially at higher baud rates In order
9. mand followed by Allow Update and Update configuration Upon RESET or power cycle for this operation the unit should begin transmitting once the start up window has elapsed If it fails to transmit the unit is still in RS 485 Mode Jewell Instruments DXA DXI Quick Start Guide v 7 2013
10. ming data can provide adjustment to averaging polarity operational mode effective filtering etc The third operational mode is a temporary RS 485 mode which behaves in the exact some fashion and the standard RS 485 mode with one exception While in the temporary RS 485 mode a power cycle or RESET command will cause the system to reboot At which point if enabled default back into RS 422 Emulation Namely the RS 485 mode if designed for 2 primary purposes to allow for the permanent transition between RS 422 and RS 485 modes by sending the turning off the RS 422 Emulation sub variable Or in this case to set the operational conditions under which RS 422 operation will permanently resume The primary method for transitioning between modes is based in 3 commands BREAK 422 Emulation ON and 422 Emulation OFF As shown before if the unit is currently set with 422 Emulation ON then the BREAK command must be used in order before the unit starts sending For convenience this Jewell Instruments DXA DXI Quick Start Guide v 7 2013 functionality is built into the DXA DXI Demo program However in order to do it manually the following procedure should be observed 1 Using a terminal emulator program or otherwise controllable data line monitor and control set up write a Hexadecimal command string that reads as the following Ox AC UVAID 02 Checksum FF FF This command consists of the BREAK concatenated with 2 Rubout and should be sent
11. ond window After the time has elapsed the VI will default back into the RS 485 mode as the unit should now be in a temporary RS 485 mode If you have previously set the unit into a RS485 state please click the toggle switch at the home page in order to enter the RS 485 mode after selecting your other DXA DXI parameters The RS 485 portion of the demo program still decodes the outputs for you but when the unit is polled but also has several pre constructed command inputs for the change of primary characteristics The majority of these are changing ON OFF characteristics with 2 exceptions For more detailed explanations of the pre constructed command input functions please refer to the DXA DXI Manual Jewell Instruments DXA DXI Quick Start Guide v 7 2013 Select Desired function During continuous polling the other controls are disabled X Output Y Output 0 000 0 000 Filter Off On Sampling Rate 0165 5Hz _ Poll Continuous Samples J 1 low cutoff freq fi Continuous Averaging On _ 3 0 5000 order J2 R5422 Emulation off __ End Program lt __ Select Normal Polarity _ Allow Update Save to Flash_ E EPE x Select Reverse Polarity _ Of the two commands which take inputs within the DXA DXI Demo program the poll continuous command polls does not take the input field as an argument to send to the unit Instead the poll continuous function uses the input field to control the rate at whic
12. to see a full list of commands please refer to your DXA DXI User Manual Jewell Instruments DXA DXI Quick Start Guide v 7 2013 D Default Address Partial Fixed Command Listing In order to quickly begin integrating your DXA DXI unit in your application the following section will outline commonly used commands with fixed default addresses and pre calculated checksums Acknowledges are provided for the commands that execute them A command which address both axes simultaneously will respond with acknowledges independently from each axis Sequence Acknowledge Poll X E Using your DXA DXI Demo Program Included with your DXA DXI Digital Inclinometer was a Demonstration Software installation After uncompressing the folder from the media provided install the Labview virtual instrument VI Instruments Please select the com port whether the unit is an accelerometer or inclinometer baud rate and communication mode and hit OK Com Port comi E Jewell Instruments DXA DXI Quick Start Guide v 7 2013 Upon program launch you are presented with the operational mode selection for your unit Please select your operating mode baud rate the COM port of your RS 485 422 reader and if you are interfacing with a DXA or DXI Unit The factory default values are RS 422 amp 38400 Baud Due to the nature of emulated RS 422 operation on the DX unit the sub program within the DXA DXI demo is primarily a reader However since t
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