DRV2624 Datasheet, PDF (33/79 Pages) Texas Instruments – DRV2624 Ultra Low Power Closed-Loop LRA/ERM Haptic Driver with Internal Memory

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DRV2624
SLOS893A – DECEMBER 2015 – REVISED DECEMBER 2015
Data is stored as interleaved voltage-time pairs. Voltage in the voltage-time pair is a 7-bit signed number with
range –63 to 63 when in signed data format, and a 7-bit unsigned number with a range of 0 to 127 when in
unsigned data format. The MSB of the voltage byte is reserved for the linear ramping mode.
The Time value is the number of ticks that the Voltage will last. The size of the tick depends on the
PLAYBACK_INTERVAL bit. If PLAYBACK_INTERVAL = 0 the absolute time is number of ticks × 5 ms. If
PLAYBACK_INTERVAL = 1 the absolute time is number ticks × 1 ms.
When the most significant bit of the Voltage byte is high, the engine interprets a linear interpolation between that
voltage and the following voltage point. The following voltage point can either be a part of a regular voltage-time
pair, or a subsequent ramp. The following lists the sequence of bytes:
1. Byte1 — Voltage1 (MSB High)
2. Byte2 — Time1
3. Byte3 — Voltage2
4. Byte4 — Time2
The engine creates a linear interpolation between Voltage1 and Voltage2 over the time period Time1, where
Time1 is a number of 5-ms ticks. The start value for the ramp is the 7-bit value contained in Voltage1. The end
amplitude is the 7-bit value contained in Voltage2. The MSB in Voltage2 can indicate a following voltage-time
pair or the starting point in a subsequent ramp.
8.6.9.3 Waveform Sequencer
To play haptic effects from the internal memory, the effects must first be loaded into the waveform sequencer,
and then the effects can be launched by using any of the trigger options.
The waveform sequencer queues waveform-library identifiers for playback. Eight sequence registers queue up to
eight library waveforms for sequential playback. A waveform identifier is an integer value referring to the index
position of a waveform in the internal memory. Playback begins at WAV_FRM_SEQ1 when the user triggers the
waveform sequencer. When playback of that waveform ends, the waveform sequencer plays the next waveform
identifier held in WAV_FRM_SEQ2 (if non-zero). The waveform sequencer continues in this way until the
sequencer reaches an identifier value of zero or until all eight identifiers are played whichever comes first.
The waveform identifier is a 7-bit number. The MSB of each sequence register can be used to implement a delay
between sequence waveforms. When the MSB is high, bits 6-0 indicate the length of the wait time. The wait time
for that step then becomes WAV_FRM_SEQ[6:0] × 10 ms.
The DRV2624 device allows for looping of individual waveforms by using the WAVn_SEQ_LOOP parameters.
When used, the state machine will loop the particular waveform the number of times specified in the associated
WAVn_SEQ_LOOP parameter before moving to the next waveform. Additionally, the entire sequencer of
waveforms can be looped a number of times specified by the WAV_SEQ_MAIN_LOOP parameter. The
waveform-looping feature is useful for long, custom haptic playbacks, such as a haptic ringtone.
GO
Waveform Sequencer
RAM
WAV_FRM_SEQ0[7:0]
Effect 1
WAV_FRM_SEQ1[7:0]
Effect 2
WAV_FRM_SEQ2[7:0]
Effect 3
WAV_FRM_SEQ3[7:0]
Effect 4
WAV_FRM_SEQ4[7:0]
Effect 5
WAV_FRM_SEQ5[7:0]
WAV_FRM_SEQ6[7:0]
WAV_FRM_SEQ7[7:0]
Effect N
Figure 33. Waveform Sequencer Programming
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