Hi Shiping, An ERM is a DC motor. So to change the frequency, you just need to change the rated voltage. Changing the rated voltage will change the revolutions per minute which will translate to the vibration frequency. The rated voltage can be changed via register 0x16 or by changing the RTP strength (RTP_Input) via register 0x02. For a LRA, the device will lock on to the LRA's resonance frequency. The vibration will always occur at this resonance frequency unless you use open-loop. In open-loop you can define the frequency (0x20). If you run the LRA at a frequency other than its resonance, the vibration will be very weak. The RTP amplitude can be changed the same way as above.
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