Interface ICs connect displays and keyboards, target tablet designs

May 02, 2013 // By Graham Prophet
Texas Instruments has introduced two devices to ease design constraints and reduce board space while adding functionality for tablet designs. The TCA8424 is the industry’s first human interface device (HID) over I2C, 128-key keyboard controller. It eliminates the need to program the device at production, simplifying design and speeding time-to-market.

The keyboard controller provides a cost-effective and seamless way to interface keyboards with Windows 8-based systems. The SN65DSI85 is a digital serial interface (DSI) to FlatLink interface IC that makes it easier for designers to connect graphics processors to LCD panels. The SN65DSI85 supports screen resolutions up to 2560 by 1600p in tablets, netbooks, and mobile internet devices.

It offers extended keyboard support: up to 128 (8 by 16) key scan supports standard keyboard plus additional custom keys, such as volume control, brightness control and forward/back/stop/reload/home. Competing keyboard controllers, TI says, support only 80 keys. Simultaneous key press detection generates a fixed-length, eight-byte input report, only available from TI, that can detect up to 14 simultaneous key presses, including modifiers, allowing the end equipment to be used in applications such as gaming. Hardware-coded HID and REPORT descriptors provide easy software integration into the system to ease design and speed time-to-market.

The optimised MIPI DSI interface provides dual 4-lane MIPI DSI port to dual link 18/24-bpp FlatLink and is compatible with a wide range of graphics processors up to WQXGA (2500 by 1600p) resolution at 60 frames per second. Higher video bandwidth support offers LVDS pixel clock operating up to 154 MHz, which is 20% higher than the competing solutions. Each DSI lane runs at 1 Gbps, offering a maximum input bandwidth of 8 Gbps.

The TCA8424EVM (evaluation module) showcases the capabilities and benefits of the TCA8424 in keyboard scanner applications and costs $49. An IBIS model and user’s guide are also available.

TI, www.ti.com/tca8424-pr-eu and www.ti.com/sn65dsi85-pr-eu