Freescale Semiconductor Application Note Document Number: AN4841 Rev. 1.0, 3/2014 S12ZVL LIN Enabled Ultrasonic Distance Measurement Based on the MC9S12ZVL32 MagniV Device by: 1 Petr Cholasta Introduction This application note introduces the MC9S12ZVL32 device in ultrasonic sonar application, capable of detecting an object as well as measuring the object distance. The MC9S12ZVL32 integrates a 16-bit microcontroller built on proven S12 technology, an automotive voltage regulator, a LIN interface, a VSUP module to sense automotive battery voltage and an HVI pin. The measured object distance is displayed in the FreeMASTER tool. The on-board RGB LED color is smoothly changed based on the actual object distance. The application includes the RGB LED diagnostics as well. The AMMCLIB [6] functions are used for mathematical operations. Parts of this document is the AN4841SW.zip file containing X-S12ZVL32-USLED hardware and software files. © Freescale Semiconductor, Inc., 2014. All rights reserved. Contents 1 2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Ultrasonic based measurement overview . . . . . . . . . . . . 2 2.1 Ultrasonic sensing principle. . . . . . . . . . . . . . . . . . . 2 2.2 Required compensation. . . . . . . . . . . . . . . . . . . . . . 3 2.3 Transducer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3 Ultrasonic sensing application . . . . . . . . . . . . . . . . . . . . . 6 3.1 Scheduling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.2 Burst generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.3 Echo receiver. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.4 Echo signal sampling and processing . . . . . . . . . . 11 3.5 Object distance calculation . . . . . . . . . . . . . . . . . . 11 3.6 RGB LED control and diagnostics . . . . . . . . . . . . . 12 3.7 LIN Slave node position detection . . . . . . . . . . . . . 13 4 MC9S12ZVL32 modules configuration . . . . . . . . . . . . . 14 4.1 Clock, Reset and Power Management Unit. . . . . . 14 4.2 Timer Module. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 4.3 Pulse Width Modulator . . . . . . . . . . . . . . . . . . . . . 15 4.4 Analog-to-Digital Converter . . . . . . . . . . . . . . . . . . 15 4.5 Port Integration Module . . . . . . . . . . . . . . . . . . . . . 16 4.6 Interrupt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 5 Ultrasonic sensing application demo . . . . . . . . . . . . . . . 17 5.1 Hardware . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 5.2 Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5.3 Demo set-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 6 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 7 Acronyms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Appendix AX-S12ZVL32-USLED board schematic . . . . . . . . 25 Ultrasonic based measurement overview 2 Ultrasonic based measurement overview An ultrasonic based measurement is a key part of applications dealing with non-contact object distance measurement and object detection: • Automotive safety systems — Parking distance sensor — Blind spot detection — Object detection • Level measurement (e.g. fuel) • Alarm systems • Automatic door opener • Electronic tape measures • Robotics 2.1 Ultrasonic sensing principle The ultrasonic waves are sounds of frequencies above 20 kHz, which can not be heard by humans. The applied methodology is based on measuring the pulse reflection time [2]. The ultrasonic transducer emits an ultrasonic wave pulse, see Figure 1. Once the pulse is emitted, the transducer becomes quite in order to receive object echoes. When the wave pulse reaches an object, the reflected wave, called an echo, is bounced back to the transducer. Figure 1. Ultrasonic sensing principle [1] The object distance is calculated by the following formula: tc d = ---------2 Eqn. 1 where: • d — object distance [m] • t — time delay between wave emission and echo reception [s] • c — ultrasonic sound velocity [m/s] S12ZVL LIN Enabled Ultrasonic Distance Measurement, Rev. 1.0 2 Freescale Semiconductor Ultrasonic based measurement overview Metal, wood, concrete, glass, rubber and paper objects reflect the majority of the ultrasonic waves back to transducer. These objects can be easily detected. Cloth, cotton and wool absorb the majority of ultrasonic waves, so it may be difficult to detect these objects [2]. 2.2 Required compensation The ultrasonic sound velocity is dependent on the air temperature, see Figure 2, for the following formula [1]: c = 331 3 + 0 606T Eqn. 2 where: • c — ultrasonic sound velocity [m/s] • T— air temperature [°C] It is necessary to measure the air temperature to keep the object distance calculation precise enough. ! Figure 2. Sound velocity dependency on temperature in dry air [1] S12ZVL LIN Enabled Ultrasonic Distance Measurement, Rev. 1.0 Freescale Semiconductor 3 Ultrasonic based measurement overview The strength of ultrasonic waves attenuates proportionally with object distance [2], see Figure 3. During echo processing, the attenuation needs to be compensated for to properly detect the object echo. ! "#$ "#$ % "#$ "#$ Figure 3. Ultrasonic waves strength attenuation with distance and wave frequency [2] S12ZVL LIN Enabled Ultrasonic Distance Measurement, Rev. 1.0 4 Freescale Semiconductor Ultrasonic based measurement overview 2.3 Transducer The transducer turns the electric pulses into mechanical vibration, and vice versa, using piezoelectric ceramics [2]. The transducer’s sensitivity is the highest at the piezoelement resonant frequency. The transducer’s pattern directivity allows detection of the object position in space. When the object hits the transducer lobe, the echo is received. The transducer directivity can be sharpened by an attached horn, see Figure 4. " " " ! ! #$%& () () ! ! ! " ' ! #$%& " ' " Figure 4. MA40S4R transducer receiver lobe variation with horn length and angle [2] Transducers called “combined use types” integrate both an ultrasonic sender and receiver. These devices are used in automotive applications for object detection, e.g. parking distance sensor, blind spot detection. There are the sender and receiver transducers available separately, called “dual use types”, e.g. in alarm systems and robotics. S12ZVL LIN Enabled Ultrasonic Distance Measurement, Rev. 1.0 Freescale Semiconductor 5 Ultrasonic sensing application 3 Ultrasonic sensing application The Figure 5 shows the Ultrasonic sensing application block diagram. The green boxes represent modules external to the MC9S12ZVL32 MCU, the blue boxes are MCU modules and the light brown boxes represent the software modules. Figure 5. Application block diagram The ultrasonic sonar unit uses dual use type transducers MA40S4S and MA40S4R operating at 40 kHz, see [3]. These transducers allow detection of an object at a distance of 20 cm to 4 m. The MA40S4S ultrasonic sender is driven by the PWM7 signal amplified by the burst signal generator. The object echo signal is received by the MA40S4R receiver transducer and amplified by the programmable gain amplifier. The band pass filter improves the echo signal to noise ratio. The echo signal is sampled by the ADC module and processed in the digital domain. The echo signal detection is based on the ADC sample value comparison with a preset threshold. The object distance is calculated and averaged using the AMMCLIB [6] functions and visualized in the FreeMASTER tool [5]. The measured object distance is compensated with temperature. The on-board RGB LED color control is based on the actual object distance. For a detailed description, see the following chapters. S12ZVL LIN Enabled Ultrasonic Distance Measurement, Rev. 1.0 6 Freescale Semiconductor Ultrasonic sensing application 3.1 Scheduling The Table 1 shows an application scheduling. The application is running in five time slots. The time slots from 0 ms to 30 ms are used for ultrasonic signal transmission and reception. The slot starting at 30 ms and ending at 60 ms is used for data processing, object distance calculation and visualization. Table 1. Application scheduling Time [ms] Burst generator Echo receiver Echo signal sampling and processing Object distance calculation Temperature measurement RGD LED control and diagnostics 0 - 0,135 ON - - - - - 0,135 - 1,135 - - - - - ON 1,135 - 30 - ON ON - - - 30 - 59 - - - ON ON ON 59 - 60 - - - - ON ON Note: Symbol “-” represents a module not operating. Transducers MA40S4S and MA40S4R [3] allow measurement of a maximal distance of 4 m. An echo reception minimal period, see Eqn. 1, is given by the measured maximal distance and sound velocity, see Eqn. 2, at the minimal air temperature, T = -40°C: m m c = 331 3 ---- + 0 606T = 331 3 – 24 24 = 307 06 ---s s 2d 2 4m t = ------------ = ---------------------- = 26ms c m 307 06 ---s Eqn. 3 Eqn. 4 Once the burst signal is transmitted, the echo receiver transducer is saturated for a 1ms period, see Figure 6. The minimal measured distance using Eqn. 1, calculated at maximal air temperature T = 85°C: m 1 135ms 382 81 ---t-------- cs d = = --------------------------------------------------- = 21 8cm 2 2 Eqn. 5 The Figure 6 shows the ultrasonic burst signal (yellow colored) waveform and the transducer receiver signal amplified by the PGA (blue colored) waveform. The PGA gain is changed proportionally with time, i.e. with object distance. The pink colored waveform displays the PGA gain change on the waveform signal edge. S12ZVL LIN Enabled Ultrasonic Distance Measurement, Rev. 1.0 Freescale Semiconductor 7 Ultrasonic sensing application In Figure 6 can be seen the object reflection at a distance of 2.2 m (blue colored waveform) at 25°C: m 12 8ms 346 45 ---s t-------- cd = = ------------------------------------------------ = 2 2m 2 2 Eqn. 6 Figure 6. Signal overview S12ZVL LIN Enabled Ultrasonic Distance Measurement, Rev. 1.0 8 Freescale Semiconductor Ultrasonic sensing application 3.2 Burst generator The PWM module channel 7 generates the burst signal, see Figure 7, the pink colored signal. Figure 7. Burst signal The burst signal drives the ultrasonic burst circuitry to generate pulses with an amplitude of 20 Vpp, see Figure 7, the yellow colored signal. The signal amplitude is given by the PWM signal duty cycle, set to 38%, and the L/C tank circuit ratio, see Figure 8. The MA40S4S ultrasonic transducer sender emits an ultrasonic wave pulse into the air. Figure 8. Burst generator S12ZVL LIN Enabled Ultrasonic Distance Measurement, Rev. 1.0 Freescale Semiconductor 9 Ultrasonic sensing application 3.3 Echo receiver When the ultrasonic wave hits the object, the echo is sent back to the MA40S4R transducer receiver, see Figure 9. The echo signal is amplified using the Programmable Gain Amplifier (PGA) to compensate the ultrasonic waves strength attenuation that is proportional to the object distance. Figure 9. Programmable gain amplifier circuitry The PGA gain control is based on the actual time measurement, see Table 2. Table 2. Programmable gain amplifier gain control Distance [cm] Time [ms] Gain [-] PT0 PT1 PT2 0 - 20 0 184 Input Input Input 20 - 30 1,135 184 Input Input Input 30- 60 1,765 376 Output low level Input Input 60 - 80 2,941 600 Input Output low level Input 80 - 110 4,706 784 Output low level Output low level Input 110 - 140 6,471 1040 Input Input Output low level 140 - 170 8,235 1248 Output low level Input Output low level 170 - 400 10 1600 Output low level Output low level Output low level The integrated band-pass filter improves the echo signal-to-noise ratio and acts as an ADC anti-aliasing filter as well. The band-pass filter design combines passive components and a relatively low U3 transition frequency to obtain the required band pass filter characteristic, with a center frequency of 40 kHz, see Figure 9. S12ZVL LIN Enabled Ultrasonic Distance Measurement, Rev. 1.0 10 Freescale Semiconductor Ultrasonic sensing application 3.4 Echo signal sampling and processing The object echo signal is sampled using the ADC module. The ADC module samples the data with an 8-bit resolution and a sampling speed of 2.2 us per one sample. When using the 40 kHz ultrasonic transducer, approximately eleven ADC samples are taken per single signal period, see Figure 10. %!&# # ! " !# $ Figure 10. Echo signal sampling and processing The ADC sampled data processing is software-based. The ADC data is compared with the ADC sample threshold, which is set to 3.5 V. Where there is software comparator first match, the first pulse time is captured (time stamp). From now on, each software comparator match increments the signal strength counter (number of samples) and the signal maximal amplitude is worked out. When there is no software comparator match for a maximum period of 68 us, the echo end is promoted. The echoes parameters are sorted into a three dimensional array capturing: • First sample time • Number of samples • Maximal amplitude 3.5 Object distance calculation The echo reception is finished when a 30 ms period has expired, starting from the burst signal transition. As the first step, the echo with the maximal amplitude is singled out. Echoes with an amplitude below 80% of this maximal amplitude are discarded. As the next step, the echo with the maximal number of samples is singled out. Echoes with a number of samples below 25% of this maximal number of samples are discarded. The described filtering process allows elimination of weak object reflections, that appear at the sides of the transducer’s lobe and disturb the desired object distance measurement. S12ZVL LIN Enabled Ultrasonic Distance Measurement, Rev. 1.0 Freescale Semiconductor 11 Ultrasonic sensing application As the last step, the echoes are sorted by value of the first sample time. The echo with the shortest period is promoted as the desired object echo. The object distance is calculated, see Eqn. 1, with sound velocity compensated for by the actual temperature, see Eqn. 2. Calculation is proceed in 16-bit fractional arithmetic using AMMCLIB [6]. The actual temperature is measured by the on-chip temperature sensor. The calculated object distance value is then averaged using a digital 2nd order IIR low-pass filter with a 2 Hz transition frequency. The IIR filter is part of the AMMCLIB [6]. The object distance is measured in millimeters and reported, as depicted in Table 3. Table 3. Object distance reporting 3.6 Object distance [mm] Measured distance RGB LED color RG LED color 0 - 199 0 Red Red 200 - 349 Object distance Red and Green Red and Green 350 - 499 Object distance Green and Blue 500 - 4000 Object distance Blue more than 4000 65535 (0xFFFF) Green RGB LED control and diagnostics The on-board RGB LED color control is based on the measured object distance, as depicted in Table 3. The PWM module drives the LED with a 16-bit resolution, enabling a smooth change of the LED color. The RGB LED diagnostics module reports the actual LED average current, calculated using the LED voltage and applied PWM duty cycle. The actual LED voltage is sampled by the ADC when the LED is turned ON, approximately 3 us for red, 6 us for green and 9 us for the blue diode after the PWM signal falling edge. The sampled value is used to calculate the diode resistor voltage. As the resistor voltage and its resistance is known, the diode peak current is calculated. The average current value is calculated using the known PWM duty cycle, and the diode peak current during a 1ms time slot from 0.135 ms to 1.135 ms, see Table 1. The calculation is carried out in 16-bit fractional arithmetic using the AMMCLIB [6]. More information can be found in AN4842 [7]. S12ZVL LIN Enabled Ultrasonic Distance Measurement, Rev. 1.0 12 Freescale Semiconductor Ultrasonic sensing application 3.7 LIN Slave node position detection The on-board LIN switch hardware is designed to support LIN Slave node auto-addressing and daisy-chaining, see Figure 11. The LIN_IN and LIN_OUT LIN signal lines are either connected or disconnected based on the MCU PS0 output pin logic level, see Table 4. ! " ! " Figure 11. LIN signal line switch When the system is powered-up, the LIN_IN (J1) and LIN_OUT (J2) LIN signal lines (pin 4) are disconnected. The LIN Master unit communicates to the closest LIN Slave unit only. The LIN Master unit sends the LIN configuration frame. Once the LIN Slave address is configured, the LIN_IN and LIN_OUT node LIN signal lines are connected and the LIN Slave configuration is repeated for the following node in the line. The cycle is repeated until the configuration of the LIN network slaves is not finished. Table 4. LIN signal line switch control MCU PS0 pin LIN_IN and LIN_OUT High level Disconnected Low level Connected S12ZVL LIN Enabled Ultrasonic Distance Measurement, Rev. 1.0 Freescale Semiconductor 13 MC9S12ZVL32 modules configuration 4 MC9S12ZVL32 modules configuration The Ultrasonic sensing application uses the following set of peripheral modules: 1. Clock, Reset and Power Management Unit (CMPU) 2. Timer module (TIM) 3. Pulse Width Modulator (PWM) 4. Analog-to-Digital Converter (ADC) 5. Port Integration Module (PIM) 6. Interrupt (INT) The modules’ configuration and usage is described in the following chapters. Detailed information on the MCU modules can be found in the MC9S12ZVL32 reference manual [4]. The application software is developed to meet the following specification: • Object distance ultrasonic measurement in the range of 20 cm to 4 m at 25°C • Object distance measurement compensation for the temperature • Echo signal processing in the digital domain • RGB LED control and diagnostics • FreeMASTER enabled For detailed info, see Section 5, “Ultrasonic sensing application demo” 4.1 Clock, Reset and Power Management Unit The Clock, Reset and Power Management Unit (CMPU) sets the CPU clock to 64 MHz and the bus clock to 32 MHz using the Internal 1 MHz clock signal. The Internal 1 MHz reference clock is selected as the source clock for the PLL (CPMUREFDIV_REFDIV = 0, CPMUREFDIV_REFFRQ = 0). The PLL VCOCLK frequency is set to 64 MHz (CPMUSYNR_SYNDIV = 31): VCOCLK = 2 SYNDIV + 1 1MHz Eqn. 7 The VCOCLK signal frequency is divided by 1 (CPMUPOSTDIV_POSTDIV = 0). This is used as the 64 MHz core clock ECLK2X signal and the 32 MHz bus clock ECLK signal. The chip temperature sensor is enabled (CPMUHTCTL_HTE = 1). 4.2 Timer Module The TIM channel 0 is running as an application scheduler time base. The TIM channel 0 compare output is configured as no action on a channel compare event (TIM0TCTL2_OL0 = 0, TIM0TCTL2_OM0 = 0). The TIM channel 0 interrupt is enabled (TIM0TIE_C0I = 1). The timer single tick is configured to 1us (TIM0TSCR2_PR = 5). S12ZVL LIN Enabled Ultrasonic Distance Measurement, Rev. 1.0 14 Freescale Semiconductor MC9S12ZVL32 modules configuration 4.3 Pulse Width Modulator The Pulse Width Modulator module generates the ultrasonic sensor burst signal and controls the on-board RGB LED. The PWM module channels operate in 16-bit resolution mode (PWMCTL_CON01 = 1, PWMCTL_CON23 = 1, PWMCTL_CON45 = 1, PWMCTL_CON67 = 1). The PWM clock A equals the 32MHz bus clock (PWMPRCLK_PCKA = 0) and the PWM clock B equals 16 MHz (PWMPRCLK_PCKB = 1). The channels PWM1, PWM3, PWM5 generate a 244 Hz PWM starting with a low-level polarity (PWMPOL1 = 0, PWMPOL3 = 0, PWMPOL5 = 0) to control the RGB LED. As a clock source, clock B is selected. The channel PWM7 generates a 40 KHz PWM starting with a high-level polarity (PWMPOL7 = 1) and a duty cycle of 38% to control the ultrasonic transducer sender. As a clock source, clock A is selected. The PWM1, PWM3, PWM5 channels are enabled (PWME_PWME1 = 1, PWME_PWME3 = 1, PWME_PWME5 = 1). The PWM7 channel is enabled only to generate the burst, see Section 3.1, “Scheduling". 4.4 Analog-to-Digital Converter The Analog-to-Digital Converter is used to sample the echo signal and LED voltage. The ADC clock is set to 8MHz (ADC0TIM = 1). The ADC module is configured to access mode via the data bus (ADC0CTL_0_ACC_CFG = 2). The ADC is running in trigger mode (ADC0CTL_0_MOD_CFG = 1). The end-of-list interrupt is enabled (ADC0CONIE_1_EOL_IE = 1). Based on the application scheduler described in Section 3.1, “Scheduling", the ADC module is periodically reconfigured every 30 ms. In the first 30 ms period, the ADC module samples the echo signal using the single command sequence list (ADC0CTL_1_CSL_BMOD = 0) and the two result value list (ADC0CTL_1_RVL_BMOD = 1) with 8-bit resolution (ADC0FMT_SRES = 0). The command sequence list drives the ADC to convert 15 consecutive samples of the echo signal. With an ADC 8-bit resolution, an end-of-list interrupt arises every 34us and sampled data is processed. The double buffer mode allows a continuing echo signal sampling, while the sampled data from the other list is processed. The following 30 ms period, the ADC module samples LED voltage and on-chip temperature sensor voltage using the single command sequence list (ADC0CTL_1_CSL_BMOD = 0) and the single result value list (ADC0CTL_1_RVL_BMOD = 0) with 10-bit resolution (ADC0FMT_SRES = 2). The LED voltage is recalculated to the LED average current, see Section 3.6, “RGB LED control and diagnostics". S12ZVL LIN Enabled Ultrasonic Distance Measurement, Rev. 1.0 Freescale Semiconductor 15 MC9S12ZVL32 modules configuration 4.5 Port Integration Module The Port Integration Module is used to drive the RGB LED, see Section 3.6, “RGB LED control and diagnostics", control the PGA, see Section 3.3, “Echo receiver”, and control the LIN switch, see Section 3.7, “LIN Slave node position detection”. The port pins PT3, PT4 and PT5 can be used to debug the application by enabling either the ULTRASONIC_APPLICATION_DEBUG or LED_APPLICATION_DEBUG macros, see Table 5. The pins share SCI and TIM modules as well. Table 5. Application debug 4.6 MCU pin ULTRASONIC_APPLICATION_DEBUG LED_APPLICATION_DEBUG PT3 ADC end-of-list interrupt - PT4 PGA gain changed ADC end-of-list interrupt PT5 Time slot expired PWM falling edge generated Interrupt The Interrupt module sets the interrupt priorities as follows, starting with the highest priority: 1. The ADC0 end-of-list - samples are ready for processing 2. The TIM channel 0 - time slot expired 3. The PIM Port P - PWM module signal falling edge captured S12ZVL LIN Enabled Ultrasonic Distance Measurement, Rev. 1.0 16 Freescale Semiconductor Ultrasonic sensing application demo 5 Ultrasonic sensing application demo The ultrasonic sensing application demo can be build using attached AN4841SW.zip file containing X-S12ZVL32-USLED board hardware and software files. 5.1 Hardware The X-S12ZVL32-USLED board, see Figure 12, is built using the AN4841SW.zip hardware files. These files include the board schematic, bill of materials, gerber files and an instruction for board manufacturing. Figure 12. The X-S12ZVL32-USLED board The X-S12ZVL32-USLED board contains, see Section Appendix A, “X-S12ZVL32-USLED board schematic": • MC9S12ZVL32 LQFP32 MCU, see [4] • LIN Slave node position detection hardware • Ultrasonic sensing circuitry: — Burst module — Programmable gain amplifier — Sender and receiver transducers • RGB LED with diagnostics hardware • Reverse battery protection • BDM enabled S12ZVL LIN Enabled Ultrasonic Distance Measurement, Rev. 1.0 Freescale Semiconductor 17 Ultrasonic sensing application demo 5.2 Software The software files are packed as the MC9S12ZVL32_UDSD_REV1.exe file available in AN4841SW.zip file. The application is developed using the CW10.3 environment. The MC9S12ZVL32_UDSD_0N22G_AMMCLIB_v_1_0_0.elf file can be found in the project FLASH folder. For code download, the P&E USB Multilink Interface is used. The ultrasonic sensing application demo shows: • Object distance measurement in the range of 20cm to 4m at 25°C • Object distance measurement compensation for the temperature • Smooth RGB LED color control based on the actual object distance • RGB LED diagnostics • FreeMASTER tool displays: — Actual object distance — RGB LED average current • Integrating the AMMCLIB [6]. 5.3 Demo set-up The demo set-up is depicted in Figure 13. The demo is designed to be able to run either with or without the FreeMASTER tool. The demo user chooses the actual object distance visualization. Figure 13. Demo Set-up S12ZVL LIN Enabled Ultrasonic Distance Measurement, Rev. 1.0 18 Freescale Semiconductor Ultrasonic sensing application demo Follow the instructions for a complete demo set-up: 1. Install the FreeMASTER tool [5] on the PC used 2. Connect the +12 V/100 mA DC power supply to the X-S12ZVL32-USLED board at J1, LIN_IN: a) GND to J1 pin 1 b) +12 V to J1 pin 3 3. Turn ON the power supply 4. Connect the P&E USB Multilink Interface to the X-S12ZVL32-USLED board at J4 5. Open the “MC9S12ZVL32_UDSD_LED.pmp” file, available in the project AN4841SW.zip file 6. Go to the FreeMASTER file Project/Options folder and check the settings as depicted in Figure 14 and Figure 15 7. Run FreeMASTER communication by File/Start Communication 8. Put an object (e.g book, paper, etc.) in front of the ultrasonic transducers U2 and U4. The RGB LED color will change smoothly based on the actual object distance, see Section 3.6, “RGB LED control and diagnostics": a) Red - object closer than 20 cm b) Red and Green combination - object distance between 20 cm and 35 cm c) Green - object distance 35 cm d) Green and Blue combination - object distance between 35 cm and 50 cm a) Blue – object distance more than 50 cm 9. The object distance is displayed on the FreeMASTER page, see Figure 16 10. The RGB LED average current is displayed on the FreeMASTER page, see Figure 17 11. The RGB LED can be controlled, see Figure 17: a) OFF b) Red and Green combination c) Red, Green and Blue combination S12ZVL LIN Enabled Ultrasonic Distance Measurement, Rev. 1.0 Freescale Semiconductor 19 Ultrasonic sensing application demo Figure 14. FreeMASTER Communication configuration Figure 15. FreeMASTER MAP Files configuration S12ZVL LIN Enabled Ultrasonic Distance Measurement, Rev. 1.0 20 Freescale Semiconductor Ultrasonic sensing application demo Figure 16. FreeMASTER object distance display S12ZVL LIN Enabled Ultrasonic Distance Measurement, Rev. 1.0 Freescale Semiconductor 21 Ultrasonic sensing application demo Figure 17. FreeMASTER RGB LED average current S12ZVL LIN Enabled Ultrasonic Distance Measurement, Rev. 1.0 22 Freescale Semiconductor References 6 References 1. 2. 3. 4. 5. 6. 7. Wikipedia, www.wikipedia.com Ultrasonic Sensor Application Manual S15E-5, www.murata.com MA40S4S and MA40S4R Datasheet, www.murata.com MC9S12ZVL Family Reference Manual, available at freescale.com FreeMASTER Run-Time Debugging Tool, available at freescale.com/freemaster Automotive Math and Motor Control Library Set, available at freescale.com/AutoMCLib AN4842, S12ZVL LIN Enabled RGB LED Lighting Application, available at freescale.com S12ZVL LIN Enabled Ultrasonic Distance Measurement, Rev. 1.0 Freescale Semiconductor 23 Acronyms 7 Acronyms ADC Analog-to-Digital Converter AMMCLIB Automotive Math and Motor Control Library Set BDM Background Debug Module CMPU Clock, Reset and Power Management Unit DC Direct Current HVI High Voltage Input IIR Filter Infinite Impulse Response Filter INT Interrupt ISR Interrupt Service Routine LIN Local Interconnect Network MCU Microcontroller Unit PC Personal Computer PGA Programmable Gain Amplifier PIM Port Integration Module PWM Pulse Width Modulation RGB LED Red, Green, Blue Light Emitting Diode TIM Timer Module USB Universal Serial Bus VSUP Voltage Supply S12ZVL LIN Enabled Ultrasonic Distance Measurement, Rev. 1.0 24 Freescale Semiconductor X-S12ZVL32-USLED board schematic Appendix A X-S12ZVL32-USLED board schematic For this schematic, please refer to “X-S12ZVL32-USLED.pdf”, attached with the pdf of this Application Note. 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