Lumissil integrates touch and lighting control in MCUs

Lumissil Microsystems has introduced two 32-bit microcontrollers combining capacitive touch sensing, addressable RGB lighting control, and mixed-signal functions for industrial and automotive human-machine interfaces.

The IS31CS9202 and IS32CS9202 integrate an Arm Cortex-M0+ processor operating at up to 50MHz, alongside dedicated peripherals for touch detection, lighting communications, serial networking, and analogue measurement. The devices are intended to consolidate several control functions that might otherwise require separate integrated circuits.

The IS31CS9202 addresses industrial and consumer equipment, while the IS32CS9202 provides an automotive-oriented variant with a higher specified maximum operating temperature. Both belong to the CS9202 family and share the principal processing and peripheral architecture.

Each device includes 256KB of embedded Flash memory and 16KB of SRAM, with error-correction functionality. Lumissil divides the SRAM resources between data and direct memory access functions, allowing supported peripherals to exchange information without requiring the processor to handle every individual transfer.

The microcontrollers also incorporate a DMA controller that manages transfers between memory and appropriate peripherals. This can reduce processor involvement in routine data movement, leaving additional execution time for application software, although actual performance depends on the configuration and concurrent workload.

One principal function is a capacitive touch-key controller with 24-bit measurement resolution. Capacitive interfaces detect changes in electrical capacitance associated with an object approaching or contacting a sensing electrode, enabling control surfaces without conventional mechanical switches.

The technique can be used behind suitable insulating surfaces, allowing the electrical sensing structure to be separated from the user's contact area. This can simplify the construction of sealed interfaces where exposed mechanical controls would otherwise require protection against moisture or contamination.

Capacitive measurement remains sensitive to the surrounding electrical and mechanical arrangement. Electrode geometry, nearby conductive materials, grounding, surface conditions, and interference can influence the signals used to distinguish an intended touch from environmental variation.

The CS9202 family supports up to 25 touch keys in 32-pin configurations or 39 keys in 48-pin configurations. These figures depend on the package and available connections rather than representing a fixed number of independently accessible inputs on every version.

The touch controller includes a dedicated shield output, active proximity sensing, and a pseudo-random sequence intended to improve electromagnetic interference behaviour. Shielding can help manage unwanted capacitive coupling, while proximity sensing provides a means of detecting an approaching object before conventional contact is registered.

Interference is particularly relevant in systems combining touch detection with switching power electronics and lighting control. Rapid electrical transitions can introduce noise into nearby sensing circuits, making filtering, PCB layout, and sensitivity adjustment important parts of the completed design.

The controller's 24-bit specification describes its measurement resolution. It does not establish 24-bit absolute accuracy or guarantee that every minute change in capacitance can be reliably distinguished under arbitrary operating conditions.

Lighting communications are handled through Lumissil's LumiBus interface, which supports control of up to 256 external addressable RGB LEDs over one communication channel. This allows application software to coordinate the behaviour of compatible lighting devices without requiring a separate microcontroller solely for the lighting interface.

The function is distinct from providing 256 individual current-regulated LED outputs. The external addressable LEDs and their associated circuitry remain responsible for their electrical power requirements, while LumiBus supplies the relevant communications function.

Addressable RGB lighting can provide indications of operating state, control selection, and changes in user-interface behaviour. In automotive cabins, lighting may be coordinated with touch controls or other electronic functions, requiring application software to manage input events and the corresponding visual response.

Combining the two functions within one microcontroller reduces the number of interfaces between separate devices. The resulting behaviour still depends on the firmware, the selected lighting components, and the communication timing supported by the completed arrangement.

The family also includes a serial video bus controller for compatible display or lighting-related communication functions. This provides a further interface option without establishing that the microcontroller can independently replace a graphics processor or operate every conventional video interface.

CAN FD provides a route for communication with other controllers, with Lumissil specifying support for data rates up to 10Mbps. The devices also include SPI, I2C, and enhanced UART interfaces, including support for LIN 2.0/2.2 functions.

These communications resources allow the microcontroller to exchange commands and measurements with other embedded devices. The achievable operating rate and reliability of a complete network depend on its transceivers, cabling, topology, and electrical environment.

For applications requiring analogue inputs or outputs, the devices incorporate a 14-bit sigma-delta incremental analogue-to-digital converter, a 12-bit successive-approximation ADC, an 8-bit digital-to-analogue converter, and four analogue comparators with programmable thresholds.

The converters and comparators support functions such as measuring sensor signals or evaluating selected voltage conditions. Their suitability for a particular measurement depends on input range, noise, conversion timing, and the accuracy required by the application.

Other peripherals include eight channels of 16-bit pulse-width modulation, timer and capture functions, a quadrature encoder interface, watchdog timers, and an internal temperature sensor. The family offers up to 42 general-purpose input/output connections, depending on the selected package.

The combination of processing and peripheral functions allows a single controller to manage user input, lighting commands, equipment communications, and selected measurement tasks. Lumissil identifies automotive centre-stack controls, entertainment consoles, keyless-entry functions, boot controls, and heating and air-conditioning systems among its intended applications.

Both devices operate from a 2.5V to 5.5V supply. The industrial IS31CS9202 is specified for temperatures from -40°C to +85°C, while the automotive IS32CS9202 extends the upper limit to +125°C.

Lumissil lists the automotive device as AEC-Q100 and ASIL-B. Those descriptions concern the manufacturer's product qualification and safety-related positioning; they do not mean that an assembled automotive control system automatically meets ISO 26262 or a particular functional-safety requirement.

The manufacturer offers 32-pin and 48-pin QFN package configurations, including wettable-flank options, together with a 48-pin LQFP configuration within the family. The available packages differ by device variant, so package selection must be checked against the required peripheral connections and temperature rating.

Wettable-flank packages expose part of the solderable connection at the package edge, helping support suitable optical inspection methods during PCB assembly. The effectiveness of inspection depends on the soldering process and the equipment used by the manufacturer.

Lumissil has listed the CS9202 devices for sampling and provides product documentation and evaluation resources. The company has not disclosed confirmed volume-production lead times or application-specific performance measurements for the newly introduced family.