Haptics: More actuators needed? No problem.


The problem:

“Haptics” refers to the feeling of tactile feedback and control that can enhance the user experience with touch screen electronic devices. Haptics technology is being used within various human-machine interfaces to create new functional surfaces and textures. While manufacturers of personal electronics like smartphone and tablets have been the first to implement this new technology, haptics is also beginning to find adopters among designers of automotive and industrial equipment.

Unlike consumer electronics, the haptics implementation in automotive and industrial equipment typically requires much larger interfaces, which require multiple actuators and present different design concerns. For example, automotive infotainment touch screens are often larger than ten inches, and the use of a single actuator to vibrate an entire screen or various localized areas would be impractical.  In an application like this, multiple actuators are needed to provide strong and consistent haptic feedback to the user. 

The solution:

TI recently announced a design tool that allows users to integrate and prototype with haptics for multiple actuator applications. The DRV2605LEVM-MD evaluation module is an evaluation platform for the DRV2605L (DGS package type). The tool includes an ultra-low-power MSP430F5510 microcontroller (MCU), terminal output support for up to eight LRAs or ERMs, an embedded waveform library pre-licensed from Immersion and capacitive touch buttons to demonstrate the capabilities of the DRV2605L haptic driver.

Figure 1: Multi-driver EVM

The DRV2605LEVM-MD demonstrates how multiple haptic drivers with the same slave addresses can be set up independently but played simultaneously. The board integrates the TCA9548A I2C switch to control which I2C lines of the eight possible DRV2605L drivers are connected to the master input I2C bus. The switch has the ability to select any combination of channels to connect to the master input I2C bus. The board also integrates an ultra-low-power MSP430F5510 MCU with USB interface capabilities and boot strap loading (BSL) functionality. The USB interfacing provides the user flexibility in controlling the DRV2605L without having to modify the firmware. The BSL functionality simplifies the firmware updating process without the additional hardware or use of a separate development environment. This design can be scaled to fit any application, with any number of actuators required.

Figure 2: Multi-actuator haptics system-level block diagram

In addition to the multi-driver board, a graphical user interface (shown in Figure 3) complements the usability of the DRV2605LEVM-MD since it allows full real-time independent control over the eight haptic drivers. This enables the user to evaluate the benefits that haptics provides with a click of a button.

Figure 3: GUI for DRV2605LEVM-MD

Imagine: Haptics for more enjoyable, less distracted driving

Multi-driver boards open the possibilities to use haptics in so many different applications. For automotive use, this design can be used for a steering wheel with gestured peripherals controls for controlling various tasks in the car. This interactive steering wheel with flexible capacitive grid circuits and pressure sensitive film embedded around the steering wheel could determine finger and hand gestures on the wheel. The gestures not only map to specific tasks for infotainment controls but can be wired up to driver controls for equipment like windows and side mirrors. Also in the steering wheel example, the DRV2605LEVM-MD could be integrated to alert the user that the audio volume was turned up 3 or 4 clicks, avoiding the need for the user to take their eyes away from the road and look at the controls display. 

The possibilities are endless with haptics, and we can’t wait for the use of multi-driver applications to expand. Visit our haptics forum and post your questions to continue the conversation about tactile feedback and control.

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