ME-210 Unicoder Product Manual
Contents
1. Unicoder time is recommended Velocity is calculated from the Period using the relation V 1 P 489ns where the Period P is measured in terms of multiples of 489ns giving a velocity in encoder ticks per second Unicoder ME 210 Product Manual 12 Name Set Distance Code D 0x44 Params mnopocpst a 32 bit count of encoder ticks Returns a orm Description This command sets the current number of ticks distance Motion that occurs after this will result in the current number of ticks changing based on the current resolution and direction of rotation For example if the AS5040 Prog register CCW bit is 0 clockwise rotations of the shaft will cause the current number of ticks to increase counter clockwise rotations will case it to decrease Name Get Distance Code D 0x44 Params none Returns mnoparst a 32 bit count of encoder ticks Description This command returns the current measured distance the shaft has rotated so far since reset or the last setting of distance using the Set Distance command Name Get Angle Code VV 0x57 Params none Returns mnop the current measured angle 0 to 1023 Description This returns the current angle in encoder ticks referenced to the current Zero Index value in the AS5040 Prog register 0 by default Full 10 bit resolution is always returned Name Get Period Code P 0x50 Params none Returns mnoparst a 32 bit time betw2. the customer s control system NOTE as the RC servo s feedback potentiometer has been removed to allow the ME 210 to be mounted the RC servo control circuit is no longer provided directly with the feedback signal it needs to close the loop As a result some other means must be provided as described in points 1 and 2 External to an RC servo angle positioning By mechanically coupling the ME 210 Unicoder encoder to the RC servo output shaft externally the RC servo control electronics continue to provide angle control using the internal potentiometer for feedback Meanwhile the customer provided controller can use the ME 210 Unicoder encoder to sense the actual position of the shaft which is heretofore otherwise not able to be determined Other Applications The ME 210 Unicoder encoder is well suited for all kinds of rotary motion sensing Shaft The ME 210 Unicoder encoder s 125 diameter shaft is not designed to be load bearing Case retention The case can be press fit in a hole properly undersized for the nominal Unicoder dimention of 394 x 438 Other mounting schemes are possible Unicoder ME 210 Product Manual 3 Material Warning the white plastic parts of the ME 210 are manufactured using 3D printing technology via the Stratasys FDM process and are made from ABS plastic They are quite strong but will separate between layers if stressed too much Communications The ME 210 Unicoder encoder provides one p
3. Manual 14 Name Get Pulse Width Code M Ox4D Params none Returns mnop a signed 16 bit pulsewidth delta Description This command returns the current pulse width delta or if the servo pulse generator is off it returns 0x8000 Unicoder ME 210 Product Manual 15 Table 1 Servo Compatibility The ME 210 s rectangular shape fits in the potentiometer recess of some makes and models of hobby servos The following is an incomplete list Manufacturer Model GWS SO3N sSoO3T SOSTXF SO6 Hitec HSS22HD Note if your specific servo is not listed it may still fit However you will have to open up the servo case to determine the shape and size of the potentiometer Many models use a round potentiometer the result of which is that the currently shipping versions of the ME 210 would be incompatible Opening of any RC servo will most likely violate it s manufacturer s warranty Note some servos such as the Hitec HS322HD that take rectangular potentiometers orient the potentiometer 180 degrees around compared to the GWS models So in order to use the ME 210 with them you will need to rotate the large white housing of the ME 210 as follows 1 unscrew the two T5 Torx screws a 1 4mm flat blade jeweler s screwdriver can work in a pinch 2 rotate the large white plastic housing by 180 degrees the existing screw holes in the housing will line up with the existing holes in the thin white spacer and the PCB 3 reassemb
4. NUGUTT Cs E210 LInicoder Product Manual Intelligent Incremental and Absolute High Resolution Encoder with Servo Pulse Generator 1 04 9 30 2012 Unicoder Features nonvolatile angle sensing 1024 positions per rotation measures velocity in terms of encoder ticks per second l2C command interface 4DOKHz max 3 3 volt operation I2C lines are 5 volt tolerant field upgradable firmware via RS232 readable position angle and velocity readable realtime counter for velocity calibration quadrature and index pulse output programmability o index pulse location zero angle location resolution 7 8 9 and 10 bit direction of rotation CW or CCW output modes quadrature sign magnitude or BLDC motor commutation servo control pulse generator OO Or Or O Description Nubotics breaks new ground with this unique new sensor Combining the best of both incremental and absolute encoders while providing new information such as total distance travelled programmable index pulse and angle origin and instantaneous velocity using an intelligent bus I2C the Nubotics Unicoder ME 210 solves many problems for electromechanical designers And as the shaft and case are designed to replace rectangular potentiometers used for angle sensing in many standard size RC servos robot builders now have a powerful new way to measure joint position wheel velocity total distance travelled and more In addition to controlling and querying the included ma
5. SCII n and is returned for all commands which are Unicoder ME 210 Product Manual 4 invalid for any reason bad CommandCode illegal characters in the parameter fields wrong command length premature command termination due to receipt of a Sync command or failure to perform the command CommandCode and associated parameters are returned for all valid get commands in order to return the values queried The factory default I2C Slave Address for the Unicoder is 0011000 0x18 this is the upper 7 bits of the 8 bit I2C address byte where the least significant bit indicates the direction of transfer 1 read 0 write per the I2C standard The complete 8 bit I2C address byte would then be 0x30 or 0x31 7 6 5 a li 2 oo 0 0 a fe 0 0 A common source of error when first using any I2C device results from using the wrong slave address Some I2C APIs want the 7 bit value and others want the 8 bit value For example the Ridgesoft RoboJDE s I2CMaster transfer method wants the 8 bit value whereas the Savage Innovations OOPIC wants a 7 bit value EndOfLine is indicated implicitly by means of the number of bytes written to the slave the Unicoder by the master your robot controller After writing the slave address CommandCode and parameter bytes as required by the command the master simply ends the transfer by signaling a STOP condition after receiving ACK on the last byte The master can optionally request the return value of t
6. ate clock such as that provided by a crystal oscillator driven microcontroller Compensation should then be applied to period or velocity measurements Name Reset Code R 0x52 Params none Returns none Description This command resets the device after reset the values of the user modifiable constants will be retrieved from nonvolatile memory and made active Name Set Constant Code FPF 0x46 Params mn op two 8 bit values mn is the constant to change and op is the value to change it to Returns a orm Description This command lets you directly modify any user modifiable constant in the Unicoder see the table on p 7 for details Please do not modify any constants if you don t know what you are doing These are stored in volatile RAM and so will be forgotten after reset or power cycle use the Store Constants In Nonvolatile Memory command below to retain any custom settings NOTE 1 you may write any number of constants up through the end of the constant table simply by sending multiple bytes before issuing an I2C STOP NOTE 2 current firmware versions ignore the baud rate constant as the Unicoder only supports asynchronous serial mode for boot loading which is fixed at 38400 baud The I2C master sets the bit rate for I2C mode not the I2C slave i e the Unicoder so the baud rate constant does not play a role in I2C mode NOTE 3 all changes to constants take place immediately thu
7. een recent ticks Description This command returns the period time between encoder ticks the unit of time measured is in multiples of 489ns If the FilterPeriod MODE bit is set to 1 then the values of the FilterN and FilterK constants will be used to control the frequency response of a single pole digital Infinite Impulse Response IIR low pass filter the period measurements will be fed to this filter every 20ms The Velocity measurement is calculated from this filtered Period measurement Unicoder ME 210 Product Manual 13 The filter takes the following form Pn average period for all encoder ticks during the previous 20ms Fn Fn 1 FilterN FilterK Pn FilterK FilterN Fn is the value returned by the Get Period command when FilterPeriod is 1 If the FilterPeriod MODE bit is set to 0 then the period and thus the velocity as well will not be filtered to remove noise In this case this command returns the elapsed time in multiples of 489ns between the most recent two encoder ticks The Velocity measurement is calculated from this unfiltered Period measurement Note that because the clock oscillator of the ME 210 Unicoder encoder is only accurate to 2 calibration by periodically monitoring elapsed Unicoder time is recommended Name Coast Code C 0x43 Params none Returns a orm Description This command turns off the servo pulse generator allowing a servo whose control pin is connected
8. ers to be written and also read in the same command In that case you must issue separate write and read requests Parameters are specified in binary format with the least significant byte first in order to be compatible with SMBus standards For example one could set the current distance to 500 decimal 1F4 hexadecimal units by issuing the following command START SlaveAddr Write Ack D a F4 Ack 01 Ack STOP From START Addr Write D _ Master SDA Wied Goes 0 01000100 E N 00000001 From WC SDA Where D is the 8 bit ASCII value for the capital letter dee 0x44 and in this case Ack represents the I2C notion of acknowledgement not the Unicoder Ack character In this case because only 16 bits of a 32 bit parameter were written the Unicoder automatically sign extends the 16 bit value to 32 bits so 01F4h becomes 000001F4h Unicoder ME 210 Product Manual ME 210 Command Set Modifier abbreviations c single character modifier usually ascii 0 or 1 mn single 8 bit byte in I2C mode mnop single 16 bit word in I2C mode least significant bytes first mnopgqrst single 32 bit dword in I2C mode least significant bytes first Name Code Hex Params Response Read Meaning written Communication Commands Sync we are synchronized Echo echo back nibbles in reversed order Informational Commands Name 5 byte string device name Uc Unicoder firmware version XX Status current dev
9. gnetic encoder chip Austria Microsystems AS5040 the ME 210 also provides an optional RC servo control pulse generator as a convenience This would allow the user to control and query an RC servo completely over I2C ME 2 10 Parts List 1 ME 210 encoder preassembled 2 6 eight lead color coded cable sold separately Installation Internal to an RC servo continuous rotation The ME 210 Unicoder encoder can be press fit in the rectangular depression inside a standard size RC servo depending on make and model once the RC servo s feedback potentiometer has been removed a common operation when converting an RC servo for continuous rotation operation By adding an ME 210 Unicoder encoder a customer supplied controller can accurately measure and control the operation of a continuous rotation servo Internal to an RC servo angle positioning In this application the feedback between shaft angle as sensed by the ME 210 and control of the RC servo s DC motor must be provided in one of two ways 1 External to the RC servo a customer developed controller produces RC servo control pulses to drive the RC servo electronics while using the ME 210 as a feedback device using a control system such as a PID position loop to effect desired motion 2 External to the RC servo a customer developed controller which includes a DC motor driver directly controls the RC servo s DC motor itself again using the ME 210 as a feedback device for
10. h is returned if currently disabled Upload Firmware connect pin 5 to TTL level serial RX pin 6 to TTL level serial TX upload via NDi protocol at 38400 baud The wCLoader exe sample program implements this protocol n 6E not acknowledge returned for illegal commands ill formed commands Unicoder ME 210 Product Manual 7 User Modifiable Constants Default AS5040 Prog Low Byte AS5040 Prog High Byte ZeroLo Servo Control Pulse Neutral Zero Motion Value Low Byte I2CADR_ I2C slave address 8 bit address LSB is ignored as that is the I2C W R bit CHANGE TAKES PLACE IMMEDIATELY ZeroHi FilterN FilterK Bit Name O I2C Mode 1 RS232Mode 2 HexComms 3 ShortMode 4 InvertServo 5 FilterPeriod 6 unused 7 unused Servo Control Pulse Neutral Zero Motion Value High Byte Digital IIR low pass period filter denominator Digital IIR low pass period filter numerator Meaning indicates this device uses I2C this device does not support RS232 except for firmware upgrades this device only supports binary communications not ASCII hex use compact return data format omit command code as first byte servo control pulses on TP2 are high for 20ms current pulse width Period amp velocity measurement are processed by a digital IIR low pass filter whose characteristics are set by the FilterN and Filterk constants set to 0 for compatibility with future firmware revisions w Baud Ra
11. he command using a REPEATED START or a separate START in read mode and request a single byte For complex query commands which both require you to write one or more parameters and also read one or more return values you would first issue a START the slave address with the WRITE bit set the CommandCode and any required parameters a repeated START condition the slave address with the READ bit set and then the return values can be read Your master would read as many bytes as it required or until an I2C NACK condition occurred It would then signal a STOP condition Alternatively in a single master environment separate START STOP conditions can occur for each phase of a complex query command first write the command and its parameters if any which may be required to specify what is being queried e g which digital I O pin then a read transaction will read the CommandCode plus the returned parameters Be sure to compare the CommandCode to that which you originally issued to make sure the parameters are what you expect NOTE This non standard method of reading parameters was added to Unicoder ME 210 Product Manual 5 support access from Via MiniITX boards and others under Linux In that environment the I2C sensor library can be used to communicate with I2C peripherals such as Devantech SRFO8 sonar rangers as well as the Unicoder Most Unicoder commands can be issued with a single library call except for commands which require paramet
12. hysical interface for transmission of commands and status information I2C Connection to I2C is via J1 External 4 7K ohm pull up resistors on both SDA and SCL are required for proper I2C operation IMPORTANT reading commands which require the ME 210 Unicoder encoder to return data will employ I2C clock stretching to hold off the master your controller until data is available Unpredictable results occur if clock stretching is not respected by your controller Clock stretching means that the slave will hold SCL low until data is available after which it will release SCL The master should detect this and then continue the transfer Each Unicoder command has the following structure CommandCode param1 param2 EndOfLine where CommandCode is either an 8 bit value between 0x41 ASCII A and 0x5A ASCII Z or the special value 0x2E ASCII the Sync command Commands can be set commands action commands or get commands Parameters and return values can be 8 16 or 32 bits in length Each Unicoder command returns one of the following results Sync EndOfLine Ack EndOfLine Nack EndOfLine CommandCode param1 param2 EndOfLine Sync is the 8 bit value 0x2E ASCII It indicates that the Unicoder confirms receipt of a Sync command Ack is the 8 bit value 0x61 ASCII a and is returned for all set or action commands that were valid and successfully processed Nack is the 8 bit value Ox6E A
13. ice status see below Get Time read current 32 bit system time in multiples of 489ns clock 7s_accurate to 2 so use this to calibrate velocity and period measurements Control Commands Reset reset the device reboot Set Const set constant number mn to value op multiple sequential bytes can be written Store Consts store all constants in nonvolatile memory gets value of constant mn multiple sequential bytes can be read Get Const query currently measured velocity in encoder en as second signed 16 bit value least significant byte first Set Distance 44 mnopqrst set current distance 32 bit signed integer least significant byte first short transfers will be sign extended Get Distance 44 none D mnopqrst query current distance travelled 32 bit signed Integer least significant byte first Get Angle w 57 none query current shaft angle resolution and location of zero can be modified via constants 5 and 6 Get Period P 50 none P mnopqrst query time between last two encoder ticks in multiples of 489ns Servo Control Pulse Generator Experimental requires AS5040 Mode 2 Sign Magnitude Get Velocity Coast stop issuing servo control pulses on TP2 Set Pulse enable and set servo control pulse generation on width TP2 range is 2047 centered at zero position which is specified in constants 7 and 8 Get Pulse return current pulsewidth value bytes 00 80 16 width bit value 8000
14. le the ME 210 being sure not to over tighten the screws as doing so can strip the plastic threads Unicoder ME 210 Product Manual 16 Connector Pinout Pin Quadrature Sign Magnitude Recommended Color 2 Orange 5 Violet NOTE pin 1 has a square pad on the PCB the rest have round pads Pin 1 is adjacent to the unpopulated part CC2 pin 8 is adjacent to capacitor CC1 which is itself adjacent to the U2 the 3mm square black integrated circuit Unicoder ME 210 Product Manual 17 Specifications Value Min Max Supply Voltage Vcc 3 0 3 6 Supply Current 18 1 26 8 Resolution 64 1024 Shaft Diameter 125 Shaft Length 375 a seat o Case Length 438 s PCB Width 500 a as Overall Width 060 Po Overall Length S13 ee Overall Height 1 07 as Interfacing Examples Please visit http www nubotics com to view and download example code for Ridgesoft RoboJDE Java and other controllers Support Please visit the Unicoder support forum at http www nubotics com forums viewforum php f 5 Document History Rev 1 0 initial draft Rev 1 01 final Rev 1 02 added color codes Rev 1 03 cables sold separately note about plastic material used note about rotating housing to fit some servos Rev 1 04 clarify byte order of multi byte parameters use of baud rate constant immediacy of changing i2c address constant and others identification of pin 1 vs pin 8 on connector including photos fixed spelling error
15. oder To cancel a partial command string in I2C mode stop the master transfer after the incorrect number of bytes for the specific command Name Echo Code E 0x45 Params mn 8 bit value to be echoed back Returns nm 8 bit echo value with nibbles reversed Description This command is used to test communications between your master program and the Unicoder The nibbles are reversed to ensure that your program is not communicating with some other device which happens to echo back characters in an unmodified fashion Name Name Code N Ox4E Params none Returns NUcx where xx is the firmware version Description This command lets you confirm that your program is talking to a Unicoder the Uc part of the name string and also to determine the current firmware version 5 ASCII characters are always returned regardless of physical interface type RS232 or I2C Name Status Code S 0x53 Params none Returns S mnop 8 bits of status see p 9 for bit definitions Description This command lets you determine the current operating mode of the Unicoder Name Get Time Unicoder ME 210 Product Manual 10 Code T 0x54 Params none Returns mnoparst a 32 bit time in multiples of 489ns Description This command returns the elapsed time in multiples of 489ns since the last reset Use this command to compensate for oscillator drift by comparing successive readings with a more accur
16. s Produced by Noetic Design Inc 25 NW 23 PL STE 6 PMB 181 Portland OR 97210 Copyright 2009 2012 Noetic Design Inc All rights reserved Unicoder ME 210 Product Manual l l k
17. s changing the I2C address of the Unicoder takes place immediately so the next command must be to the new address Unicoder ME 210 Product Manual 11 Name Store Constants In Nonvolatile Memory Code F 0x46 Params FF FF two 8 bit values with all bits set to one Returns a or n Description This will result in the storage of all user modifiable constants NOTE the flash locations used have a finite lifespan so do not use the Store Constants command more than necessary Name Get Constant Code PF 0x46 Params mn a single 8 bit value specifying the constant number to read Returns F mn op where op is the 8 bit value of constant number mn Description This will return the current value of any of the user modifiable constants You can read any number of constants up through the end of the constant table simply by reading multiple bytes before issuing a STOP command Name Get Velocity Code V 0x56 Params none Returns mnop the current measured velocity of the shaft in encoder ticks per second Description This returns the actual measured velocity of the encoder shaft Use of the FilterPeriod MODE bit is recommended to reduce the affect of AS5040 nonlinearity errors and mechanical assembly tolerances on velocity measurements see Get Period below Note that because the clock oscillator of the ME 210 Unicoder encoder is only accurate to 2 calibration by periodically monitoring elapsed
18. te Selection constant address 3 Value Baud Rate O 1200 4 38400 1 4800 5 57600 2 9600 6 115200 3 19200 7 230400 experimental Value Baud Rate Unicoder ME 210 Product Manual 8 AS5040 Prog Bit Definitions constant addresses 5 and 6 Bit Name Meaning Number 0 1 Mode output mode 0 default 1 quadrature 2 sign magnitude 3 BLDC commutation 2 3 Div resolution 0 10 bit 1 9 bit 2 8 bit 3 7 bit 4 IndexLen 0 1 pulse wide 1 3 pulses wide 5 14 Zero Idx location of zero angle and index pulse always 10 bit resolution 15 CCW 0 angle increases clockwise 1 angle increases counter clockwise Status Bit Definitions returned by the status command Bit Name Meaning Number 0 MagDEC asserted when magnet moved away from IC magnetic field strength decreasing MagINC asserted when magnet moved toward IC magnetic field strength increasing linearity alarm angle may be invalid magnet outside of xYZ tolerances CORDIC overflow angle is invalid magnet outside of XYZ tolerances offset compensation finished startup complete data valid Unicoder ME 210 Product Manual 9 Command Set Detailed Descriptions Name Sync Code Ox2E Params none Returns Description This command serves as an early test of communications with a Unicoder to determine of the Unicoder is present and the I2C slave address matches between your master program and the setting of the Unic
19. to TP2 to coast to a stop Name Set Pulse Width Code M 0x4D Params mnop a signed 16 bit pulsewidth delta in units of 489ns Returns a or n Description This experimental feature of the Unicoder ME 210 allows the Unicoder to generate 50Hz RC servo control pulses on test point 2 TP2 this can be cancelled using the Coast command The active portion of the servo control pulses will be the sum of the Servo Control Pulse Neutral constant values with this command s specified 16 bit signed delta parameter The default values for the Servo Control Pulse Neutral constants result in an active time of 1 5ms which is the industry standard RC servo neutral pulse width The signed delta parameter must be between 2047 and 2047 corresponding to RC servo control pulse widths between 0 5ms and 2 5ms The InvertServo MODE bit controls whether the signal output on TP2 is active high or active low If InvertServo is 0 then the pulses will be high for Neutral Delta 489ns then low until a total of 20ms has passed If InvertServo is 1 then the pulses will be low for Neutral Delta 489ns and high for the rest of the period This can be useful if your servo requires a buffer or level shifter a gate a transistor etc to provide a high enough control signal voltage and that buffer or level shifter inverts The ME 210 can output at most 3 3v on TP2 which might not be enough for some servos to register Unicoder ME 210 Product
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