Q&A CMR3100
You will find here the most frequently asked questions and answers about CMR3100 Consumer Gyro.
If you do not find here the answer you are looking for, please contact our support [at] vtitechnologies [dot] com
Functionality and specification
1. Q: How many bits does CMR3100 have in output?
A: CMR3100 has 16bit output data, i.e. two byte wide registers per axis.
2. Does CMR3100 have measurement range selection?
A: Measurement range is user selectable with four options: ±2000dps, ±1000dps, ±500dps, ±250dps.
3. Q: What is the maximum SPI clock rate?
A: It’s 500 kHz.
4. Q: Does CMR3100 support 3-wire SPI (CSB tied to GND)?
A: No. 3-wire SPI is not supported, CSB has to be pulled high in the end of communication frame.
5. Q: Is the I²C interface disabled when SPI interface is used?
A: In case of multi slave SPI bus CMR3100’s I²C interface can be disabled with a register command.
6. Q: Does CMR3100 have self test?
A: CMR3100 has embedded continuous self diagonstics which indicates that gyro primary resonance loop is locked and MEMS is resonating correctly. Self diagnostic result can be read from CMR3100 internal register. If SPI communcation is used, the self diagnostic result is transferred automatically out in every SPI frame. Please see Product Family Specification for more details.
7. Q: Does CMR3100 have reset pin?
A: No. Power-on or register command can be used to reset the device.
8. Q: Does CMR3100 have FIFO function?
A: Yes.
9. Q: Does CMR3100 have internal temperature compensation?
A: No. Detection method gives robust result without compensation.
10. Q: Does CMR3100 have temperature data output?
A: No.
11. Q: Can you measure wider than +/-2000 dps range?
A: Dynamic range is approx +/- 3000 dps with FS=2000dps setting. However, this will be limited by the potential offset due to calibration, soldering and temperature dependency.
12. Q: What does CMR3100 frequency response value mean? Can CMR3100 be used to measure human scale gestures?
A: Even though gyro can measure for example 2000°/s angular rate, it can not react on indefinitely fast changes of rotation rate. Gyro frequency response describes how fast rotation rate changes can the sensor detect. CMR3100 frequency response is wide enough to measure human motion without a delay in user interface and gaming applications.
13. Q: Can CMR3100 be used for OIS?
A: CMR3100 is optimised for user interface and gaming.
14. Q: Is CMR3100 providing measurement results from same moment of time?
A: SPI: Output register data refresh is enabled when CSB is '1'. Angular rate output registers are refreshed when the MSB register address is written. Use decrement reading to ensure XYZ data from the same moment.
I2C: Angular rate output registers are refreshed when the address of the register is written. Use I²C burst mode while reading to ensure XYZ data from the same moment.
Design Support
15. Q: What are the available support tools?
A: Component documentation, samples on breakout board and demokit. Please check our development tools pages.
16. Q: How can I ensure my communication works correctly?
A: A good practise is to read a known fixed register content such as REVID or I2C_ADDR to ensure the write and read operations.
17. Q: What is the MAX sampling rate of the CMR3100 demo?
A: Demo supports the CMR3100 maximum output data rate (375Hz).
18. Q: What is the purpose of GND area on PWB under the component?
A: It minimizes the noise coupled from the PWB. This amount of potentially coupled noise highly depends on the design (product & layout) so the need of the ground plane needs to be defined case by case.