! ! LIDAR!Lite%Operating%Manual"
Contents
1. X 1 6 Current Consumption lt 2ma 1Hz shutdown between measurements lt 100ma continuous operation Busy status using 12C External Trigger input PWM outputs Laser Sensor PCB Technical Specifications PIN detector without optics ss General sd Technical Specifications NEP PIN detector 12nW rms 1 5pF detector capacitance 1mm virtual detector size Min Detectable signal 1nW 256 integrated bursts maximum integration time Transmit Power laser 1 5Watts peak 14mm 3amps drive 75um single stripe laser junction Transmit Power LED 200mW within 3 degree beam lamp LIDAR Lite Operating Manual Page 3 of 41 Revised 12 2 2014 LIDAR Lite Specifications Continued LED Pin with Laser Pin with System Parameters LED Pin Optics Optics 5mm Plastic LED 6 5mm Plastic LED 6 75um 1 watt TX Emitter divergence divergence 4mrad 14mm optic 5mm Plastic Si PIN ramin GIAE 14mm diameter RX Detector 30 FOV 8mm effective aperture 3 FOV aperture 10 FOV P Ax TX RX Focal Length 25mm 25mm Max Range 1Hz 3 meters 10 meters 30 meters 30 target Max Range 1Hz 5 meters 20 meters 60 meters 90 target 0 025 meter 0 025 meter 0 025 meter lt 0 02 sec Max Rep Rate 100 Hz 100 Hz 100 Hz 10Hz Class 1 1 Uses standard surface mount PIN detector instead of T 1 lamp style detector 2 Uses custom laser housing amp optics with surface mount PIN detector instead of T 1 lamp style2. 1 selects the longer distance 0 selects the shorter distance LIDAR Lite Operating Manual Page 24 of 41 Revised 12 2 2014 The detection criteria is controlled by bit positions 1 and 2 If Select Range Criteria is zero the system will always select the strongest signal present In this case regardless of the number of returns the strongest return will be measured If Select Range Criteria is one than the longer or shorter valid return will be selected without consideration of relative signal strength Select Max Range selects the longer or shorter return Select Second Return selects the raw data associated with the rejected return pulse allowing the reprocessing of the second data set to extract distance and signal strength To reprocess the data Select Second Return is set to one without changing the state of bits 1 and 2 of register 75 This followed by sending a value of 1 to the command register 0 initiating a reprocessing of the pulse return data After reading the second pulse distance data Select Second Return should be set back to zero to return to the desired pulse detection criteria LIDAR Lite Operating Manual Page 25 of 41 Revised 12 2 2014 Power Management Two registers can be used to manage power consumption over the acquisition cycle and during idle time between measurements Bit positions 0 3 of the Mode Control Register 4 control the power state automatically entered after
3. E N TO EE E 15 Orear ONEN W a a E 15 MOUE ORY I II a aS E eee an AEE EA E E E S EE E A E E E E E 15 Ae O SC NS eara E EO E E E E E 16 SENAC HON Proce Seienn A EE EN A E A E A E 17 OT NRE COO pases a E E nieasae aucwenseenncanaeeronea 19 Processing the Correlative PUSE srpen rinner AERE E REE E EET 21 POCO SAS aoe E E EE E E E E E E E E E 22 SPENTO e E EEEE EE EE 23 Aee E EE E 4 E eee eet E EE EE E AA E AEN EE E E E E A EEE T ree 23 Processing of multipole reflections sesiroryriisrnieranr s aere EA edict ac AENEA E A AEE Oa 24 POWER Manac me Mi sessen ro AS EEN ANE REE AT SEEE S 26 Downloading a Correlation CGO oscsiirisisiserissisisreisvsasorarvenesikansnnis israse ndis SNA ENN DESEAN SNEKKE SENAN ole on nagede ese ces KAANANI KE RENSES Ha nia 28 Append A Control ReRe Ste S eee eer ten nn ene nr rer eee Tee Terr Terre heer T Teer errr TTT 29 MO WW apace a citar E aps cn a seo vec tse pc ace anc acon pecan argon tect asco cq men cerns aa dinette ree nae nu noeamnns E armen eee aeeaenneiaee 29 be Peril Ole ROIS BCI Serceasreuswaenssea ceecuwanca unease acalieneanneacseaanoanswancmudoanfonniussay soci ataunccnt E EE 29 Correlation Core External Control Registers wes isacsesuteradaeeetecseaceanacateseavionswalenavosuuatacussnauaoswbeadsoatiotadeaneeunceutseaveutanstenvnnenslonivede 30 Detailed Register Descriptions Internal ssssssssesesesescsesesesecesesecesecesesecesecesesececesesesesesecesecesececeseceseceseoe 31 Detailed Register Des
4. approximate rms value of the noise supporting diagnostics or as part of a voltage control feedback signal supporting an avalanche photo detector biasing 2 Prior to starting signal acquisition the correlation memory is cleared and the transmitter is activated to generate a burst signal pattern that is stored in a signature memory that is used as key element in the correlation process 3 Signal acquisition begins with the activation of the reference portion of the transmitter followed by the feeding of the signal pattern necessary to generate the optical reference signal which then passes directly to the receiver photo detector After amplification and zero crossing detection this record is stored in the signal memory LIDAR Lite Operating Manual Page 17 of 41 Revised 12 2 2014 4 The stored reference signal record is then correlation processed using the transmit pattern stored in the signature memory as a template which is then added to any correlation data previously processed and residing the reference portion of the correlation memory 5 Next the signal transmit portion of the transmitter is enabled and the outgoing optical signal goes out to a target and the signal return is amplified detected and stored in signal memory 6 Asin step 4 the stored signal record is correlation processed and then added to any correlation data previously processed and residing the signal portion of the correlation memory 7 As the signal and referenc
5. by the elimination of the reference pulse acquisition and performing the acquisition without a prior DC compensation step The setting of bit position 6 adjacent to the velocity mode selection bit in register 4 suppresses the acquisition of the reference pulse and the loading of 3 into the command register 0 performs an acquisition without the normal DC compensation step The DC compensation needs to be performed every few seconds when the sensor is first warming up but once thermally stable compensation can occur at a much slower rate LIDAR Lite Operating Manual Page 23 of 41 Revised 12 2 2014 Processing of multiple reflections It is possible to receive multiple valid return signals from a single measurement if the beam illuminates more than one surface along the beam path This situation may be encountered when the beam clips or passes through an object in the foreground Because of the inverse square law behavior of the return signal double the distance get four times less signal a very small area illuminated area near the sensor may produce a much stronger signal than that from the desired target Ranging objects through a window can produce a strong shorter range signal masking the longer target or conversely it may be desirable to detect a window in the foreground that may only produce a small reflective signal relative to a larger distant reflection The sensor has the capability to process two distinct reflections as long as they are s
6. detector LIDAR Lite Operating Manual Page 4 of 41 Revised 12 2 2014 Laser Safety CLASS 1 LASER PRODUCT CLASSIFIED EN IEC 60825 1 2007 Complies with US FDA performance LASER APERTURE standards for laser products except for deviations pursuant to Laser Notice No 50 dated June 24 2007 PULSEDLIGHT LLC LIDAR Lite Manufacture Date July 2014 PulsedLight LLC PO Box 691 Bend OR 97709 sensors pulsedlight3d com LIDAR Lite is a laser rangefinder that emits laser radiation This Laser Product is designated Class 1 during all procedures of operation This means that the laser is safe to look at with the unaided eye However it is very advisable to avoid looking into the beam and power the module off when not in use No regular maintenance is required for LIDAR Lite In the event that the unit becomes damaged or is inoperable repair or service of LIDAR Lite is only to be handled by authorized factory trained technicians No service of LIDAR Lite by the user is allowed Attempting to repair or service the unit on your own can result in direct exposure to laser radiation and the risk of permanent eye damage For repair or service please contact PulsedLight directly for a return authorization No user should modify LIDAR Lite or operate it without it s housing or optics The Operation of LIDAR Lite without a housing and optics or modification of the housing or optics that exposes the laser source may result in direct exposur
7. length establishes the portion of correlation memory allocated to the return signal The value is broken in to upper and lower nibbles where the lower indicates the starting location and the upper nibble the end point The nibble value multiplied by 64 is its location in memory A value of Oxf indicates the end of the record with a value of 1024 control_reg 4 Acquisition mode control establish the enabled acquisition functions such as velocity measurement lower power consumption states and inhibiting the reference External register space control_reg 0x43 Laser power control control_reg 0x4b Range Processing Criteria for two echoes Max signal Max Min Range control_reg 0x65 Power management Sleep states Signal Acquisition Process After loading new acquisition parameters or retaining default values a command is sent to the SPC to initiate a signal acquisition The steps of the acquisition are as follows 1 Power is applied to the receiver preamp and after a prescribed delay the DC offset at the threshold detector is adjusted to set the effective slicing level or threshold in the middle of the noise distribution The adjustment process is based on the measurement of the one zero duty cycle at the comparator output When the signal offset is nulled the duty cycle of the noise pattern approaches an average of 50 In more sophisticated applications the threshold can be offset as part of an algorithm to measure the
8. noise The narrowband filter is of most benefit in applications where specular mirror like reflective surfaces are present LIDAR Lite Operating Manual Page 14 of 41 Revised 12 2 2014 Power Conditioning Multiple voltage references are required by various functions on the LIDAR Lite board The standard PIN detector requires a DC bias voltage of roughly 8V generated by an internal voltage multiplier The use of optional APD detector requires a temperature dependent bias from 100V up to 240V depending on the selected detector This voltage bias is varied based on the temperature compensation coefficient and is applied through the external detector bias input pin A factory modification is required to allow external application of detector voltages above 30V DC A3 7V power supply is used by the receiver circuitry and is enabled by the SPC Transmitter circuitry typically uses the 5V nominal supply voltage but can be modified at the factory for an external LED Supply from 5 to 10 Volts DC By default the LED supply pin is coupled to the 5V input through isolation inductor An enable pin allows the internal 3 3 V regulator to be disabled allowing very low power consumption under shutdown conditions Operational Overview Operation of LIDAR Lite can be separated into two phases initialization and triggered acquisitions as initiated by the user During initialization the microcontroller goes through a self test sequence followed by initializat
9. or Edge Freq Ref In ze DC In Power Triggering with PWM Enable p Mode Select LIDAR Lite Operating Manual Page 12 of 41 Revised 12 2 2014 Signal Processing Core SPC The key component within the system is our SPC chip which implements PulsedLight s signal processing algorithms and primary system architecture The SPC contains four major subsystems 1 An 8 bit microcontroller provides system control and communications It contains an 12C slave peripheral 2 A500 MHz sampling clock and an associated sampler capture the logic state of the external comparator and convert the data into a slower speed 125 MHz four bit word which is sent to a correlation processor 3 Acorrelation processor stores the incoming signal and performs a correlation operation against a stored signal reference with optical burst reception and stores the result in the correlation memory with data points every 2 nanoseconds 4 Atransmit signal generator produces an encoded signal waveform with an overall duration of 500ns that consists of a varying interval pattern of ones and zeroes These outgoing signal pulses occur at a 20 KHz repetition rate and become either the reference signal or outgoing signal pulse depending on the state of the transmitter Optical Transmitter and Receiver The optical transmitter and receiver have been designed around the requirements of our signal processing algorithm The transmitter produces optical pulse bursts using signal patterns g
10. reference is scaled by 1 25 to provide a detection threshold for the correlation Figure No 1 PSF Ea File x Heip 1 l L L 1080 1100 1120 1140 1160 1160 1200 1220 1240 A start lt gt PCB Layouts BEY Cloocuments and Settin i A manaa BE Foure no 1 Qa BR iam If more than one signal is detected within the correlation record the return with the next highest signal strength is stored and is available for additional processing A flag within the status register indicates the presence of a valid second reflection such as from a window or from a shorter range object illuminated by the beam The on board processing of secondary returns is limited to weaker target reflections in the foreground The correlation record can be downloaded by the user to examine target details in post processing LIDAR Lite Operating Manual Page 20 of 41 Revised 12 2 2014 Processing the Correlative Pulse The calculation of the effective delay is based on the course location within the correlation record and the interpolated crossing between sample points For the full resolution correlation record used in the LIDAR Lite processor each sample represents 2nsec in time or roughly one foot or 3 meters To obtain a result in cm requires 30 resolution points obtained by interpolating between data points The figure below illustrates a single correlation pulse obtained by processing either the reference or signal 165 170 175 180 185 190 195 184 184 5 18
11. roughly 2X magnification of the package lens Noise Equivalent Power Background Light LIDAR Lite has been designed to operate effectively under a variety of indoor and bright outdoor solar background lighting conditions The internal optical absorption filter in combination with the detector spectral response provides a transmission band from 800nm to 1000um Outdoors this Spectral window allows roughly 14 of the total solar Irradiance to pass to the detector Assuming a solar constant of roughly 1Kwatt per meter and a full receiver field of view of two degrees we get the following calculated DC solar current and detector shot noise 1000W m 1 r 14 1 1e 4m7 27 1 cos a 2 9 _ where a is the Receiver FOV in degrees 2 degrees A an i Transmission Solar radiance off diffuse 14 of solar Area of RCVR lens Solid angle of reflections in W m Srad in m RCVR FOV Bright solar optical background 6uW Solar DC current 6e 6 Watts 6A watt 3 6e 6 A Shot noise 3 6e 6 A 2 1 6e 19 1 H2 1pA Hz Under the bright solar conditions and highly reflective diffuse background calculated above the equivalent receiver input noise floor of 1pA Hz would increase by a factor of 1 4 resulting in a slight reduction in maximum range A 20nm spectral width narrow band optical filter is available as a factory option and results in a 10 fold reduction in solar DC current or a 10 3 fold decrease in the resulting
12. the completion of an acquisition while Power Control Register 101 sets the present power saving state without requiring a distance measurement The table below summarizes the control bits of register 4 associated with power management Control Register 4 0x04 Mode Control control_reg 4 Bit 7 Bit 0 Velocity Inhibit Reference DET OFF FPGA SLEEP CLK SHUT Preamp Off Description default 0x00 Preamp Off Shutdown preamp between measurements CLK SHUT External Clock Shutdown Not used in standard LidarLite FPGA SLEEP Full FPGA sleep after measurement DET OFF Turns off detector bias after measurement Control Register 101 0x65 control_reg 101 Bit 7 Bit 0 Det Bias Disable SLEEP REYR ou OSC Disable Disable Description default 0x00 control_reg 65 Power control write only OSC Disable Disables oscillator reference Not used in LidarLite SPC RCVR PWR Disable Turns on receiver regulator decreases power consumption by 30mA when inhibited Processor sleep Reduces power to 20mA with other hardware disabled wakes on I2C transaction Send dummy prior to any command or register access operation Det Bias Disable Turns off detector bias charge pump SLEEP At the completion of a normal distance measurement or at the completion of the two measurements associated with a velocity measurement the first 4 bits of register 4 are loaded into Power Control register 101 Loading values into register 101 result
13. 0 The correlation waveform has a bipolar wave shape transitioning from a positive going portion to a roughly symmetrical negative going pulse The point where the signal crosses zero represents the effective delay for the reference and return signals Processing with the SPC determines the interpolated crossing point to a 1cm resolution along with the peak signal value The figure below illustrates a correlation record example for long range system using an avalanche photodiode or APD and laser with a processing chip with a half resolution 2 foot correlation steps and two thousand element signal record The target is at 660 meters and forms the same bipolar correlation wave shape as in the short range system but in practice the correlation waveform must be distinguished from background noise present in the correlation record A correlation record detection threshold is established based on the background noise and if no signals are detected above this threshold a no signal status indication is provided LIDAR Lite Operating Manual Page 19 of 41 Revised 12 2 2014 A Start gt PCB Layouts BIA C Cocuments and Settin A matlas TBE Figure No lt 3 23 zsm The correlation waveform is shown in more detail below To distinguish the correlation pulse from the background noise a specialized processing filter follows the envelope of the noise without being significantly effected by signal correlations present in the record This noise
14. 0kb per second Control Registers are divided between internal u P registers and external registers residing in Correlation processor The internal registers are mapped to register addresses from O to 15 hex and external registers from 40 to 68 hex Internal registers are both read and write while external registers are read or write only The most signal bit of the address byte in the I2C ane byte triggers the auto incrementing of register addresses with successive register reads or writes within an 12C block transfer uP internal Control Registers control_ reg 0x0 Command Control control_reg 0x1 Status system status control_reg 0x2 Maximum acquisition count control_ reg 0x3 Correlation record length setting control_reg 0x4 Acquisition mode control control_reg 0x5 Measured threshold offset during acquisition control_reg Ox6 7 Measured delay of reference in correlation record control_reg Ox8 Reference correlation measured peak value control_ reg 0x9 Velocity Measurement Output control_reg Oxa b Measured delay of signal return in correlation record control_reg Oxc Signal correlation measured peak value control_reg Oxd Correlation record noise floor 1 25 for setting valid signal threshold control_reg Oxe Received signal strength typical range 10 min 128 maximum control_reg Oxf 10 Calculated distance in cm difference between signal and re
15. 41 Revised 12 2 2014 Control Register 73 0x49 control_reg 73 control_reg 0x49 Measured DC value out of correlation sampler input Value based on the ratio of 1 s and 0 s read only Control Register 74 0x4a control_reg 74 Bit 7 Bit 0 sy flag Detector sel xmt Len Description Enables transmit channel 1 high side current source Enables transmit channel 2 high side current source Selects high 2x or low gain 1x setting not used in laser lite product control_reg 0Ox49 Output port write only Control Register 75 0x4b control_ reg 75 Bit 7 Bit 0 lect R Select Max Range 36 eck Range Select Second Criteria Return Range Processing Criteria for two echoes Max signal Max Min Range Controls echo processing selection 1 switches to alternative return 0 Selects data associated with detection criteria 1 selects return data based on distance 0 selects strongest return regardless of distance Control Register 75 0x4c control_reg 76 control_reg 0x4c Peak Value of 2 largest pulse in the signal correlation record read only Control Register 79 0x4f control_reg 79 Bit 7 control_reg 0x41 l laser units revisions begin with 0x01 short range 0x20 for long range lasers and Led units begin with 0x40 Control Register 81 0x51 control_reg 81 Bit 7 Bit 0 Start address startaddresi Value in the range from 0x00 0x0f starting point in correlation re
16. 5 185 5 186 186 5 The correlation waveform on the left shows a zero crossing on the falling edge around the location 185 The detail of the crossing on the right shows a linear fit from the upper crossing point at 185 with a value of 26 and a negative value at 106 of 44 The calculation of the crossing is equal to 26 26 44 30 or 11 14cm To get the total delay we multiply the index of the upper point 185 and multiple by 30 to get the course delay in cm The total delay is then 30 185 10 5550 If we have a delay for the reference waveform with a crossing at 30 30 15 or 915cm we get a measured delay of 5550 915 46 35 meters LIDAR Lite Operating Manual Page 21 of 41 Revised 12 2 2014 Processing A module within the processor analyses the correlation record looking for the largest peak waveform within the record As it moves through the record the crossing characteristics of each new larger peak is sampled At each peak the course delay to the positive sample prior to the zero crossing along with correlation values above and below the crossing and the peak value are stored With each new peak sample the previous peak and the crossing data now the next largest peak sample is stored to allow the post processing the data to extract the distance and peak value The secondary peak in some cases may be the small reflection of the beam passing through a window or possibly the reflection off objects in the foreground The figure below detail
17. PulsedLight Inc PO Box 691 Bend Oregon USA sensors pulsedlight3d com www pulsedlight3d com 1 541 639 8842 PULSED LIGHT LIDAR Lite Operating Manual December 2 2014 Table of Contents lakopa lt siela PT R nee me ee eee ae enn EE A neater Seer ne E nee eee erent ne I eee ee een eee eae eee ee 3 re ES SpE MEANE aia sa ec cae a ieee ese essed eae ds cca tc 3 LIDAR Lite Specifications Continued sssessssssosssssosssosssesssssssesssesecssesssssecssecssesssssesssecssececscecesscsoesessseseos 4 EE E A E A A A PE A A sed et ca EI EE N E E E A 5 E E E E E EEEE EEE 7 SIPE COE aaa E E E AA AAA A taser dana twioaedtumeeeeaderae 7 LIDAR Lite Signal amp Power Interface Definitions scsccsccccsceccscsccccsccccsccccsceccececescnccecsceccececesceccecsceccecesens 8 LEPO UREN TEE E EE EE E 9 Monae DINO O a A TE 10 PCB Dimensions backside viewed through board csccscccceccscecceccscesceccsccscecceccececcscesceccecsceccsscsseccuss 10 DE N E E A 11 TECHNOLO V R TE A E A eats rsa AAEE AA A 11 System Hardware OVerviE rca ts trac rcesal ES rara E EE AETA REA ANRE IAAT 11 LIDAR Lite Block DARIAN herrarna E EERE ER E 12 Sienai Procesne COGS PO oirrim EE AE AET EENE T NE AEO AE E EEE 13 Optical Transmitter and Receiver ar reteset ie aacectoncne risainia iridia EEs EE EEA ELE EN TEE NE ELANA A sansa 13 BK agana MET i E EE A EE EA N EA E E A A EAE E TN A EA E A AA E A E AAE A 14 POWE CONGOS crr aa E E E EAO
18. cord record broken into 64 element segments 1024 total Stop address Value in the range from 0x00 0x0f stopping point in correlation record LIDAR Lite Operating Manual Page 38 of 41 Revised 12 2 2014 Control Register 82 0x52 control_reg 82 Bit 7 Control Register 83 0x53 control_reg 83 Bit 7 Bit 6 Bit 0 Memory bank Reset xmt pattern 0 starts signal acquisition at zero in signal memory 1 starts at location 64 8 single bit samples per location 0 stops signal acquisition at 63 in signal memory 1 stops at location 256 8 single bit samples per location O n a 1 template memory selected 2 signal memory selected 3 correlation memory selected Control Register 87 0x57 control_reg 87 control_reg 59 Correlation Peak value reference or return scaled to 0 Oxff max peak value read only aa Used in both signal strength calculation and stored in the appropriate uP control register Control Register 90 0x5a control_reg 90 Description control_reg 5a Maximum noise within correlation record scaled by 1 25 typically between 0x10 0x30 read only LIDAR Lite Operating Manual Page 39 of 41 Revised 12 2 2014 Control Register 91 0x5b control_ reg 91 Description control_reg 5b Calculated signal strength read only l Note calculation based on the number of averaged samples and correlation peak value p Soft reset of system always occurs with write to re
19. criptions External sesesesesesesoececesesososoecesescesececesesosoececesesosoesesesesesoscesesssesoeoeceseeee 36 LIDAR Lite Operating Manual Page 2 of 41 Revised 12 2 2014 Introduction PulsedLight has targeted the need for high performance very compact optical distance measurement sensors for cost sensitive markets such as UAV s robotics and automotive These applications benefit from substantially improved measurement range high accuracy and reduced size over competing technology Our single chip processing solution in combination with minimal supporting hardware enables a new class of optical distance measurement sensors that exceed the performance of current solutions at a substantially lower cost PulsedLight s signal processing technology can be applied to applications ranging from single beam distance measurement to multi pixel applications such as line scanning or complex 3 D imaging Our single board implementation of less than one square inch allows the use of a variety of optical sources such as LED s VCSEL s Vertical Cavity Surface Emitting Lasers or edge emitting lasers Our standard detector is based on a Si PIN diode but optionally a Si APD can be used to provide greater sensitivity and range LIDAR Lite Specifications Technical Specifications 4 75 5 5V DC Nominal Maximum 6V DC PCB 4 5 grams Module 22 grams with optics and housing PCB 44 5 X 16 5mm 1 75 by 65 Housing 20 X 48 X 40mm 8 X 1 9
20. e USER Side Sensor J1 5PIN CONN La GND lt L oj 6 PWM Monitor l ots SDL OUT L4 O14 SCL QUT L3 V R31 GND Trigger 3 1D kt Ol fa 1K i TT p 0 gt e Q lo O as T a l OMI y ww l 20 gt Af LUI 6 a Tri lt rigger PWM Monitor PWM high state PWM returns to high z state and Sensor Re triggers Sensor Measurement Period Acquisition Settings Signal acquisition parameters can be easily changed to trade off system performance parameters If a high measurement rate is required then the maximum signal integration time can be reduced to decrease measurement times at the expense of somewhat reduced sensitivity and maximum range Optical transmit power can be increased by the setting loaded into the Laser Power Register High pulse power may need to be compensated with an increased spacing between pulse bursts to maintain an acceptable laser duty cycle based on thermal derating requirements If the length of the correlation record is increased to allow for longer range measurements increased processing time will decrease the measurement rate LIDAR Lite Operating Manual Page 16 of 41 Revised 12 2 2014 Key control registers impacting acquisitions Internal register space control_reg 2 Maximum acquisition count sets the maximum number of acquisition cycles with a maximum value of 255 In most cases an acquisition of 128 is adequate control_reg 3 Correlation record
21. e acquisitions are repeated the peak correlation values in the correlation record increase and would ultimately overflow the 12 bit word size To prevent this overflow condition the correlation process is terminated for either the signal or reference records when a peak signal within the record exceeds a preset maximum value slightly under overflow Once both the reference and signal records have reached their maximum values or that maximum acquisition count has been exceeded the acquisition process is terminated 8 After the signal acquisition process is complete a low pass and DC restoring filtering process typically cleans up the waveform to improve the final measurement accuracy at low signal conditions and short range This function can be disabled by resetting the filter enable bit in control register 4 for improved accuracy and resolution at longer ranges LIDAR Lite Operating Manual Page 18 of 41 Revised 12 2 2014 Correlation Record Distance measurements are based on the storage and processing of reference and signal correlation records The figure below shows a correlation record for a sensor without optics at short distances of 0 4 and 8 feet The reference record runs from 0 63 and the signal record from 64 to 130 Each sample point represents 2nsec or roughly one foot TT TTTTETTETETTETETTETETTITETETTETTET m ee eee LT Se ee ee eE SS Sa SO Oe a aan ena aaa dae eee eee es q 4 15
22. e to laser radiation and the risk of permanent eye damage Removal or modification of the diffuser in front of the laser optic may result in the risk of permanent eye damage Caution Use of controls or adjustments or performance of procedures other than those specified herein may result in hazardous radiation exposure PulsedLight is not responsible for injuries caused through the improper use or operation of this product LIDAR Lite Operating Manual Page 5 of 41 Revised 12 2 2014 Class 1 Laser Product This Laser Product is designated Class 1 during all procedures of operation Wavelength Total Laser Power Peak Mode of operation Pulse Width Pulse Repetition Frequency Energy per Pulse Beam Diameter at laser aperture 12mm x 2mm Divergence a LIDAR Lite Operating Manual Page 6 of 41 Revised 12 2 2014 Quick Start Guide 1 Make Power and I2C Data Connections as per J1 connector pin out diagram Pins 2 amp 3 are optional connections and not required 2 Initialization Apply Power to the Module The sensor operates at 4 75 5 5V DC Nominal Maximum 6V DC 3 Measurement Write register 0x00 with value 0x04 This performs a DC stabilization cycle Signal Acquisition Data processing Refer to the section 12C Protocol Summary in this manual for more information about 12C Communications 4 Periodically poll the unit and wait until an ACK is received The unit responds to read or write requests with a NACK when the se
23. enerated by the SPC When an optical reference signal is desired a separate reference transmitter is enabled and driven with the signal pattern using a reference LED fed to the optical receiver The reference transmitter has been designed to match the delay and signal shape produced by the higher power signal transmitter The signal transmitter can drive a variety of optical sources ranging from high speed LEDs higher power VCSEL laser or much higher power pulsed laser diodes For the LIDAR Lite module the signal transmit driver drives a T1 3 4 plastic packaged laser diode with a three amp peak 50 average duty cycle modulation over a burst duration of 500ns The driver has a capability to drive sources at up to 6 amps using an external DC power supply Ans LIDAR Lite Operating Manual Page 13 of 41 Revised 12 2 2014 The receiver incorporates a state of the art low noise preamplifier that is coupled to either a PIN photodiode or optionally an avalanche photodiode APD When using the higher performance APD an external regulated high voltage bias voltage is needed The APD is used to increased system sensitivity allowing either increased operating range or reduced measurement times Before reaching the high speed digital comparator specialized analog filtering shapes the return signal originating from the output of the preamplifier Bandwidth 50 MHz Receiver specification PIN diode 5 00um by 500um 1 5pF 1 8mm diameter lens 1mm
24. eparated by more than 3 5 meters and the reflection at the shorter distance does not saturate the correlation record masking the more distant object The Secondary return flag in bit position 4 in the status register 1 indicates that a second pulse has been detected The figure below shows an example of two reflections in the signal correlation record record address locations greater than 64 separated by approximately 3 5 meters T T T 200 150 j 250 gt Q 50 109 150 200 250 The sensor detection criteria may be selected to pick the shorter signal longer or the strongest strength In addition when a second pulse is encountered the other reflection can be read from the system without having to perform a new measurement with different detection criteria Control register 75 summarized below sets up the criteria for selection of the desired return when two are present Control Register 75 0x4b control_reg 75 Bit 0 elect Range Select Second Select Max Range Peta j Criteria Return Description Default value is 0x00 control_reg 0x4b Range Processing Criteria for two echoes Max signal Max Min Range Select Second Return Controls echo processing selection 1 switches to alternative return 0 Selects data associated with detection criteria 1 selects return data based on distance 0 selects strongest return regardless of distance Select Range Criteria Select Max Range
25. erminating operation Note The unit responds to read or write requests with a NACK when the sensor is busy processing a command or performing a measurement For proper operation the I2C peripheral driver needs to handle the NACK condition without a producing error condition LIDAR Lite Operating Manual Page 9 of 41 Revised 12 2 2014 20mm X 48mm X 40 mm to top of optics LIDAR Lite Operating Manual Page 10 of 41 Revised 12 2 2014 Overview Technology PulsedLight s Time of flight distance measurement technology is based on the precise measurement of the time delay between the transmission of an optical signal and its reception Our patented high accuracy measurement technique enables distance measurement accuracy down to 1cm by the digitization and averaging of two signals a reference signal fed from the transmitter prior to the distance measurement and a received signal reflected from the target The time delay between these two stored signals is estimated through a signal processing approach known as correlation which effectively provides a signature match between these two closely related signals Our correlation algorithm accurately calculates the time delay which is translated into distance based on the known speed of light A benefit of PulsedLight s approach is the efficient averaging of low level signals enabling the use of relatively low power optical sources such as LEDs or VCSEL Vertical Cavity Surface Emitt
26. ference delay control_reg 0x11 DC threshold command value control_reg 0x12 Added delay to reduce signal acquisition burst frequency control_reg 0x13 Distance calibration Signed 8 bit value adds or subtracts from distance control_reg 0x14 15 Previous measured distance LIDAR Lite Operating Manual Page 29 of 41 Revised 12 2 2014 Correlation Core External Control Registers control_reg 0x40 Command register control_reg 0x41 Hardware Version control_ reg 0x42 Preamp DC control control_ reg 0x43 Transmit power control control_reg 0x44 Processing range gate low byte control_reg 0x45 Processing range gate high byte control_reg 0x46 Range Measurement PWM output pin bit 0 used control_ reg 0x47 Acquisition status control_ reg 0x49 Measured preamp DC offset control_reg Ox4a Output port control_reg 0x4b Range Processing Criteria for two echoes Max signal Max Min Range control_ reg Ox4c i largest detected peak in signal correlation record control_reg 0x4f Software Version control_reg 0x51 Correlation record size select reference and signal return control_reg 0x52 Correlation Data access port low byte control_reg 0x53 Acquisition Settings selects ext memory access signal record select control_reg 0x57 8 Measured delay of reference or signal in correlation window control_reg 0x59 Correlati
27. floor observed in the range record LIDAR Lite Operating Manual Page 22 of 41 Revised 12 2 2014 Special Topics Velocity measurement A velocity is measured by observing the change in distance over a fixed time period The default time period is 100msec resulting in a velocity calibration of Imeters sec Velocity mode is selected by setting the most significant bit of register 4 to one When a distance measurement is initiated by writing a 3 or 4 no dc compensation or update compensation respectively to command register 0 two successive distance measurements result with a time delay defined by the loaded value into register at address Ox68 Measurement Period msec Velocity Scaling meters sec Register 0x68 Load Value 100 1m s OxC8 40 25m s 0x50 20 m s 0x28 10 1m s 0x14 Velocity is output as an 8 bit 2 s complement signed value read out from register 0x09 Velocity is the difference between the last two 16 bit distance measurements The previous distance measurement used in the velocity calculation is available from registers 0x14 and 0x15 with 14 containing the most significant byte and 15 the least To measure velocity with measurement period less than 20msec adjustment of the acquisition parameters will likely be necessary The nominal acquisition is between 10 15msec allowing insufficient time to complete the first velocity acquisition period before starting the second Measurement acquisition times can be reduced
28. gister FPGA Core reset anywritetothisregister Resets peak detectors used to process the correlation record Control Register 93 0x5d control_reg 93 Bit 7 o sign Control Register 93 Ox5f control_ reg 95 Bit 7 i i i a Measured transmit power using internal power monitor read only Description control_reg 61 Peak Index high byte read only course crossing point in the correlation record prior to zero crossing LIDAR Lite Operating Manual Page 40 of 41 Revised 12 2 2014 Control Register 98 0x62 control_reg 98 control_reg 62 Peak Index low byte read only course crossing point in the correlation record prior to zero crossing control_reg 63 Positive crossing Upper correlation pulse data value prior to zero crossing used to interpolate fine delay control_reg 64 Negative crossing Lower correlation pulse data value after zero crossing used to interpolate fine delay Control Register 101 0x65 control_reg 101 Bit 7 Bit 2 RCVR PWR Det Bias Disable SLEEP OSC Disable Disable SLEEP Bit 1 Processor sleep Reduces power to 10mA with other hardware disabled wakes on I2C transaction Send dummy prior to any command or register access operation Det Bias Disable Turns off detector bias charge pump Control Register 104 0x68 control_ reg 104 Bit 7 eT INTERPULSESPACING OO po x8 _gives 100msec pulse separation for 1m sec velocity regi
29. gisters are accessed using this command and the correlation processor cannot be ina sleep state Sample C Code Download Correlation Data to a Serial Port Using Put This pseudo code can be used as a basis for the download of correlation data for analysis bank_num memory banks in the correlation processor 1 template memory 2 last signal record 3 correlation record Function write_twi register address hex value Function read_twi register address hex number of bytes Elements number of words to be transferred read_val is 16 bit integer if bank _num 3 write_twi 0x51 0x10 points to the base of the correlation record address write_twi 0x53 char bank _num lt lt 6 selects memory bank write_twi 0x40 0x06 sets test mode select For i 0 i lt elements i read_val unsigned char read_twi 0x52 1 added to select single byte if read_twi Ox5d 1 read_val Oxff00 if upper byte Isb is set the value is negative put_dec read_val TO _Wait_ms 1 hold longer than the transfer time for the serial transfer write_twi 0x40 0x00 return to normal control null command to control register LIDAR Lite Operating Manual Page 28 of 41 Revised 12 2 2014 Appendix A Control Registers Overview The rangefinder configured using an I2C machine interface Settings control the acquisition and processing of ranging data The 12C interface supports a transfer rate up to 10
30. ing lasers for shorter range applications and increased range capability when using high power optical sources such as pulsed laser diodes System Hardware Overview The Single Board Sensor provides distance and velocity measurements in an ultra small form factor This small size is the result of PulsedLight s System On Chip SoC signal processing technology which beyond being small reduces the complexity and power consumption of supporting circuitry The system consists of three key functionalities e A Signal Processing Core SPC System on Chip solution encapsulating all the required functions in support of our proprietary range finding system architecture e An optical transmitter and receiver tied to the SPC emit and receive a proprietary optical signal pattern generated by the SPC e Power Conditioning and 12C signal filtering and buffering Please refer to the following block diagram for a full overview of the system architecture LIDAR Lite Operating Manual Page 11 of 41 Revised 12 2 2014 LIDAR Lite Block Diagram Signal Transmitter LED or Optional Laser Diode Reference Transmitter Target Comparator Optical Receiver Analog Filtering Detector Bias Voltage Power SoC Supply Conditioning Voltages Receiver and Transmitter Supply voltages System On Chip SoC Processing Core iwi Processor LI User Interface I2C Filtering and Isolation Circuit jI Detector USER I C
31. ion of the internal control registers with default values Internal control registers can be customized by the user through the I2C interface after initialization After the internal control registers are initialized the processor goes into sleep state reducing overall power consumption to under 10 milliamps Initiation of a user command through external trigger or 12C command awakes a processor allowing subsequent operation The input of a command through the I2C interfaces may initiate an acquisition or an operation to monitor or modify system parameters In the event of an acquisition request the system must first power up and initialize the external functions such as the SPC and transmit receive circuitry Acquisition begins with the transmission of a reference burst followed by a signal burst These signal bursts occur over interval of roughly 50 100us depending on the length of the selected correlation record These signal bursts are repeated until the maximum number of acquisitions have been reached as defined in the default or user settings or a sufficient number of acquisitions have been performed to achieve a maximum signal strength level At the completion of the required number of acquisition cycles the correlation results are processed to calculate the effective time delay of the reference and return within in the correlation records The total acquisition time for the reference and signal acquisitions is typically between 5 and 20ms dependi
32. ite Operating Manual Page 36 of 41 Revised 12 2 2014 Control Register 67 0x43 control_reg 67 Ref led power level control 0x0 Oxf Signal laser or led power level control 0x0 Oxf Default 0x69h control_reg 0x43 Transmit power control Led Laser drive control bits 7 through 4 ref bits 3 through 0 signal Note Maximum value set at factory lamp LED and 3amps Laser product The maximum output power of the optical source is set through a factory selected resistor which limits available current to the transmit source When using laser devices which have a much higher operating current do not increase the reference control level beyond the factory settings Increasing the reference control level may cause premature failure of the internal LED reference diode Control Register 68 0x44 control_reg 68 control_reg 0x44 Processing range gate low byte sets the staring location for range processing in the correlation control_reg 0x44 Processing range gate high byte Description PWM bit Single bit passed from microcontroller PWM output High at mode pin returns pulse width proportional distance Control Register 71 0x47 Mode Status control_reg 71 Bit 7 Bit 0 Eye safe Busy Signal Invalid Signal Invalid 1 No signal detected O signal detected Indicates that eye safety average power limit has been exceeded and power reduction is in place LIDAR Lite Operating Manual Page 37 of
33. ng the desired number of integrated pulses and the length of the correlation record The acquisition time plus the required 1msec to download measurement parameters establish a roughly 100Hz maximum measurement rate Mode Control Pin A bi directional control and status pin provides a means to trigger acquisitions and return the measure distance without having to use the 12C interface LIDAR Lite Operating Manual Page 15 of 41 Revised 12 2 2014 The pin driver in the processor has an internal current source pull up of roughly 50uA with the driver output coupled to the user pin through a protection diode allowing only sourcing current into the pin A low going transition on the mode control pin will trigger a single measurement and the pin will be actively pulled high with a pulse width proportional to distance A 1K to 10K ohm termination resistance will solidly pull the pin low to trigger an acquisition state while allowing the pin to still be pulled high during the PWM output pulse The pulse width follows a 10usec cm relationship to the measured distance or 1msec per meter A simple trigging method using a standard microcontroller interface uses a 1K ohm resistor in series with an output pin to pull the mode pin low initiating a measurement with a second port pin used to monitor the low to high output pulse width If the pin is held low the acquisition process will repeat indefinitely producing a variable frequency output proportional to distanc
34. nsor is busy processing a command or performing a measurement Optionally wait approx 20 milliseconds after acquisition and then proceed to read of high and low bytes 5 Read register OxOf returns the upper 8 bits of distance in cm register 0x10 returns the lower 8 bits of distance incm Optionally a 2 Byte read starting at Ox8f can be done Sample Code Sample code for LIDAR Lite can be downloaded by visiting https github com PulsedLight3D LIDAR Lite Operating Manual Page 7 of 41 Revised 12 2 2014 LIDAR Lite Signal amp Power Interface Definitions J2 Pin1 Top View PIN Detector MH y Side View J1 Primary signal power interface Board Connector Molex part 5023860670 Mating Connector Molex 5023800600 PLUG HSG 6POS POWER_IN 4 75 5 5V DC Nominal Maximum 6V DC Peak current draw from this input is typically lt 100 milliamps over a duration from 4 to 20ms depending on received signal strength Typical measurement times are roughly 10ms corresponding to a 2 one time using one measurement per second POWER_EN Active high enables operation of the 3 3 V microcontroller Regulator Low puts board to sleep draws lt 40 microamperes Internal 100K pull up Laser Bypass 5 20V max nominally connected to pin2 through inductor L8 removed for external LIDAR Lite Operating Manual Page 8 of 41 Revised 12 2 2014 I2C Protocol Summary LIDAR Lite has a 2 wire I2C compatible serial interface refer to 2C B
35. od of SCL An 8 bit data byte following the address loads the 12C control register with the address of the first control register to be read along with flags indicating if auto increment of the addressed control register is desired with successive reads or writes and if access to the internal micro or external correlation processor register space is requested Bit locations 5 0 contain the control register address while bit 7 enables the automatic incrementing of control register with successive data blocks Bit position 6 selects correlation memory external to the microcontroller if set Presently an advanced feature If a read operation is requested a stop bit is issued by the master at the completion of the first data frame followed by the initiation of a new start condition slave address with the read bit set one state The new address byte is followed by the reading of one or more data bytes succession After the slave has acknowledged receipt of a valid address data read operations proceed by the master releasing the I2C data line SDA with continuing clocking of SCL At the completion of the receipt of a data byte the master must strobe the acknowledge bit before continuing the read cycle For a write operation to proceed Step 3 is followed by one or more 8 bit data blocks with acknowledges provided by the slave at the completion of each successful transfer At the completion of the transfer cycle a stop condition is issued by the master t
36. on peak value of reference or signal control_reg Ox5a Correlation record noise floor 1 25 for setting valid signal threshold control_reg Ox5b Received signal strength typical range 10min 255 maximum control_reg OxS5c Reset correlator increment transmit signal pattern control_reg Ox5d Correlation Data access port sign bit control_reg OxS5e Clock synchronizer control control_reg Ox5f Measured transmit power Supports Laser safety monitoring control_reg 0x60 Measured fine delay used as part of measured delay calculation control_reg 0x61 62 Coarse delay used as part of measured delay calculation control_reg 0x63 Positive correlation sample before zero crossing correlation pulse falling edge control_reg 0x64 Negative correlation sample after zero crossing correlation pulse falling edge control_reg 0x65 Power control settings control_reg 0x68 Velocity measurement window setting register LIDAR Lite Operating Manual Page 30 of 41 Revised 12 2 2014 Detailed Register Descriptions Internal Control Register 0 0x00 control_reg 0 Description Command register 0 Reset FPGA Re loads FPGA from internal Flash memory all registers return to default values 1 Correlation processing without new acquisition used to process delay of second peak after bit O in control register Ox4b is set to 1 2 Process correlation without new acquisition used
37. ontrol_reg 6 control_reg 6 High byte of calculated delay of reference calculated after correlation record processing read only Control Register 7 0x07 control_ reg 7 Bit 7 low byte of calculated delay of reference calculated after correlation record processing read only Control Register 8 0x08 control_ reg 8 Bit 7 i Correlation Peak value reference scaled to 0 Oxff max peak value read only aaa Parameter used as part of health flag criteria LIDAR Lite Operating Manual Page 32 of 41 Revised 12 2 2014 Control Register 9 0x09 control_ reg 9 Description Velocity in 1 meters sec read only 8 bit signed value See Mode control Register 4 for information on changing the scale factor to 1m sec control_reg 10 High byte of calculated delay of signal correlation calculated after correlation record processing read only control_reg11 low byte of calculated delay of signal correlation calculated after correlation record processing read only control_reg 14 Calculated signal strength read only l Note calculation based on the number of averaged samples and correlation peak value LIDAR Lite Operating Manual Page 33 of 41 Revised 12 2 2014 control_reg15 high byte of calculated delay of signal reference calculated after correlation record processing read only l Note if the MSB is 1 then the reading is not considered valid control_reg16 low by
38. reamp between measurements is reduced power consumption and less thermal rise above ambient temperature when operating at low pulse rates 1 10 Hz Clock Disable Is not used in the LIDAR Lite product On high performance long range product a crystal oscillator reference in included on the circuit board FPGA Sleep Disables the phase lock loop based internal clock resulting in the shutdown of all the internal circuitry except for 12C interface The 12C interface still monitors buss activity and when its address is detected it initiates the activation of the internal clock The wake up time is necessary for the PLL to re lock on its internal frequency reference Detector Off Shuts off the on board charge pump generating the 8V bias to the photodiode Disabling the charge pump has negligible impact on power consumption however it eliminates the last of the periodic potential noise sources on the board LIDAR Lite Operating Manual Page 27 of 41 Revised 12 2 2014 Downloading a Correlation Record The following details simplified C code routine to download three types of record stored in the system memory The first selection is a memory bank where the last correlation template pattern is stored The last received signal record stored is in bank 2 while bank 3 stores the full correlation record See detailed descriptions of the accessed control registers in Appendix A for a detailed explanation of their function Note Only external re
39. s in immediate action execution The loading of power control register occurs after completion of the reading of the lower byte of the distance measurement register 16 When pulling data from the unit after a measurement read all other registers before reading register 16 Placing the FPGA into a sleep state results in shutting down of all internal clocks making the internal registers unavailable until the system is waken The system will automatically wake from the sleep state if a read operation is initiated using the I2C interface A dummy read command should be sent to the unit to wake it followed after roughly 10msec with the desired read or write command A measurement initiated by a write to command register O will return the system to full power operation prior to a measurement followed by a return to a sleep state afterwards Depending on the bit status various degrees of power savings are possible however larger power savings increased the time necessary for the system to return to normal operation Power Saving Mode Savings Wake up Time Nominal Power Draw 80mA Preamp off 30mA 2msec Clock Disable 10mA Imsec FPGA Sleep 40mA 10msec Det Off 1mA Imsec LIDAR Lite Operating Manual Page 26 of 41 Revised 12 2 2014 Summary Preamp off Shutting down the preamp shuts disables the 3 7V regulator supporting the preamplifier circuitry The power is stable in 1 2msec after re enabling after shutdown The advantage for powering down the p
40. s the processing flow within the correlation processor after a final correlation waveform is complete Values in Stored in External Processing flow registers space Values transferred Coarse Record delay i To microcontroller Internal register space Correlation delay in cm Positive Correlation Sam Positive Correlation Sample Seared Negative Correlation Sample i Correlation Waveform PE Number of Acquisitions F Peak Value Extraction Value Extraction y x gt Signal strength Correlation Processing Post Processing Signal Detection Flag Detection Flag The processed correlation waveform is processed and the various extracted parameters are stored in the external register space For both the reference and signal records the course record delay and the positive and negative correlation samples are processed to determine the delay in the record to the correlative peak The difference between the delay measured for the signal and reference determine the effective round trip delay to the target The delay is scaled to produce a result in centimeters Signal strength is determined by multiplying the peak value of the correlation by the scaled inverse of the number of acquisitions Itis an inverse relationship because more samples are required to increase the strength of a small signal than a larger one A valid signal is determine is determined by comparing the signal peak value with the value of the noise
41. ster calibration value o o o po O14 gives 10msec pulse separation for m sec velocity register calibration value S LIDAR Lite Operating Manual Page 41 of 41 Revised 12 2 2014
42. te of calculated delay of signal reference calculated after correlation record processing read only Control Register 17 0x11 control_reg 17 Description vonal rer ci Register shows the required DC compensation command value to maintain zero crossing offset at preamp Parameter regla used as part of health flag criteria Distance Calibration value The value is added to measured distance 8bit signed value allows increasing or decreasing the measured value Description control_reg120 Previous high byte of calculated delay of signal reference read only LIDAR Lite Operating Manual Page 34 of 41 Revised 12 2 2014 Control Register 21 0x15 control_reg 21 Description control_reg21 Previous low byte of calculated delay of signal reference read only LIDAR Lite Operating Manual Page 35 of 41 Revised 12 2 2014 Detailed Register Descriptions External Control Register 64 0x40 Command Control control_reg 64 Perform Delay calculation Processing Bits O through 2 Definitions Perform only correlation record filtering Command control register Writing to this register through the I2C interface immediately initiates a command operation Thus it is important to initiate this command only at the completion of defining other registers Control Register 65 0x41 control_reg 65 control_reg 0x42 Preamp DC control 0 255 used in DC compensation servo loop LIDAR L
43. to reprocess 3 Take acquisition amp correlation processing without DC correction 4 Take acquisition amp correlation processing with DC correction Control Register 1 0x01 Mode Status control_ reg 1 Bit 7 Bit 0 E Tri Veloci Eye Safe neta BBST mae Secondary return Signal not valid Sig overflow flag Ref overflow flag Health Complete complete Health 1 state indicates that all health monitoring criteria were met on the last acquisition 0 possible problem Ref overflow flag Overflow detected in correlation process associated with a reference acquisition Sig overflow flag Overflow detected in correlation process associated with a signal acquisition Signal not valid Secondary return Velocity complete External trigger complete Eye Safe Health status indicates that the preamp is operating properly transmit power is active and a reference pulse has been processed and has be stored Control Register 2 0x02 control_reg 2 default 0x80 Maximum Acquisition Count 0 255 Control the FPGA maximum signal integration time Stronger signal results in reduced control_reg 2 acquisition count to prevent internal register overflow Sig overflow flag and Ref overflow flag in control register 1 are set when automatic limiting occurs Control Register 3 0x03 control_reg 3 Bit 7 Bit 0 Correlation start and stop locations used for signal acquisition write only coer ee Value in the range from 0x00 0
44. us Specification Version 2 1 January 2000 available from Philips Semiconductor It can be connected to an I2C bus as a slave device under the control of an I2C master device It supports standard 100 kHz data transfer mode Support is not provided for 10 bit addressing The Sensor module has a 7 bit slave address with a default value of 0x62 in hexadecimal notation The effective 8 bit 12C address is OxC4 write OxC5 read The unit will not presently respond to a general call The I2C serial bus protocol operates as follows 1 The master initiates data transfer by establishing a start condition which is when a high to low transition on the SDA line occurs while SCL is high The following byte is the address byte which consists of the 7 bit slave address followed by a read write bit with a zero state indicating a write request A write operation is used as the initial stage of both read and write transfers If the slave address corresponds to the module s address the unit responds by pulling SDA low during the ninth clock pulse this is termed the acknowledge bit At this stage all other devices on the bus remain idle while the selected device waits for data to be written to or read from its shift register Data is transmitted over the serial bus in sequences of nine clock pulses eight data bits followed by an acknowledge bit The transitions on the SDA line must occur during the low period of SCL and remain stable during the high peri
45. x0f starting point in correlation record record broken into 64 element segments 1024 total Stop address Value in the range from 0x00 0x0f stopping point in correlation record Note With longer correlation records burst pulse period is roughly proportional to the length of the correlation record Unnecessarily long record length increases the probability of false detections LIDAR Lite Operating Manual Page 31 of 41 Revised 12 2 2014 Control Register 4 0x04 Mode Control control_reg 4 Bit 7 Bit 0 Velocity Scal Velocity Inhibit Reference z aa i DET OFF FPGA SLEEP CLK SHUT Preamp Off FPGA SLEEP Full FPGA sleep after measurement DET OFF Turns off detector bias after measurement Note used presently 1 sets the velocity measurement separation to 10msec resulting in a velocity calibration in meters sec A 0 value results in a measurement separation of 100msec Ahibithererente If 1 inhibits the acquisition of reference pulses reducing measurement times and reducing measurement variations at the expense of decreasing accuracy over time 0 allows normal operation Velocity Enable velocity measurement Velocity Scale factor Control Register 5 0x05 control_reg 5 nominal 128 Measured DC value out of correlation sampler input Value based on the ratio of 1 s and O s read only preamp Parameter used as part of health flag criteria control_reg 5 Control Register 6 0x06 c
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