Touch the difference with AT42QT1110 and STM32F091RC

TouchKey 3 Click uses the AT42QT1110, an 11-key QTouch® Touch Sensor IC from Microchip. It can be configured in several different ways, depending on the application: it can be used to support more or less sensor channels, to support direct outputs for an interrupt triggering on a specific channel, to have its #CHANGE output pin used for triggering one global interrupt whenever one of the sensors detects a touch event, or to improve the power consumption by employing the SYNC input signal for triggering sensing bursts in specific time intervals. TouchKey 3 Click uses seven capacitive sensing channels, with the #CHANGE pin routed to the INT pin of the mikroBUS™, so that an interrupt can be triggered if any of the sensors detect a touch event, for example. This can trigger an SPI read cycle only when the key is pressed, avoiding the need for constant polling of the AT42QT1110’s registers. However, the behavior of the #CHANGE pin is programmable and more information about its functionality can be found in the AT42QT1110 datasheet. The SYNC pin is pulled high and not used, allowing the click board™ to run in the Free Run mode, which enables the fastest key press detection times. #RESET pin of the AT42QT1110 is routed to the RST pin of the mikroBUS™, and it is used to reset the device and reinitialize its working parameters - either with values stored in the EEPROM or the default values that are loaded into the RAM, in case the EEPROM does not contain any saved values. SPI will not be available for 160ms after the RESET event has occurred. This pin should be pulled to a HIGH logic level to reset the device. The AT42QT1110 sensor has internal registers that are used for configuring

the working parameters of the device. The device Mode register is one of the important config registers, and it is used to control the overall operation of the click board™. Bit KEY_AC of the Device Mode register is used to set the detection triggering mode: 0 by SYNC pin or 1 by internal timer (should be set to 1, since the SYNC pin is pulled to a HIGH logic level); MODE bit: 0 for 7, or 1 for 11 channels configuration (should be set to 0 for 7 channels operation); SIGNAL bit:  0 for serial, or 1 for parallel; SYNC bit: 0 for rising edge, or 1 for zero level detect (disregarded, since the KEY_AC is set to 1); REPEAT TIME bit field: these four bits set the repeat time between the scanning intervals. If the REPEAT TIME is set to 0, the new scanning cycle will be performed immediately after the previous cycle, allowing for the fastest touch detection. The value of this bitfield is multiplied by 16ms to get the final repeat time. TouchKey 3 click also features signal processing to provide better button detection. Adjacent Key Suppression (AKS®) technology can be configured on each channel. A group of channels with the AKS® enabled will be processed so that only the detected key remains active, while other sensors will be disregarded. The other sensors with the AKS® enabled will be activated only when the currently active key is released. The sensor channels for which AKS® is not selected will retain the ability to sense touch simultaneously. This technology allows better key accuracy and less false detections in applications requiring key press detection precision. Detection Integration (DI) is another technology used to sense the key press better. When the button is first pressed, a counter is started. If the counter expires

and the sensor channel still detects a key press, that keypress will be declared true. Else it will be disregarded as false. This serves as a kind of debouncing and prevents false detections. DI technology is implemented per sensor. The AT42QT1110 IC has EEPROM memory, which can store current RAM settings. All the registers are kept in RAM, and after the power-on reset event (POR), the values stored in the EEPROM memory will be automatically copied to the registers. Else, the registers will be loaded with the default values. All these functions can be accessed and configured via the SPI bus. The SPI communication can be either in Quick SPI mode or full SPI mode. While working in the Quick SPI mode, the device will send a sequence of 7 bytes containing the essential data, such as the detection and error status of the channels. In this mode, no-host MCU commands are required, and this sequence will be clocked out continuously from the AT42QT1110 IC. Quick SPI mode is enabled by setting the SPI_EN bit in the Comms Options setup register. All the SPI pins and the chip select pin are routed to the appropriate pins on the mikroBUS™. Onboard SMD jumper labeled VCC SEL selects the power supply and logic voltage level. This click board can work with both 3.3V and 5V MCUs. The provided TouchKey 3 Click library contains functions used to configure the device and read touch events comprehensively and intuitively. The included example application demonstrates the usage of these functions, and it can be used as a reference for a custom design.

Nucleo-64 with STM32F091RC MCU offers a cost-effective and adaptable platform for developers to explore new ideas and prototype their designs. This board harnesses the versatility of the STM32 microcontroller, enabling users to select the optimal balance of performance and power consumption for their projects. It accommodates the STM32 microcontroller in the LQFP64 package and includes essential components such as a user LED, which doubles as an ARDUINO® signal, alongside user and reset push-buttons, and a 32.768kHz crystal oscillator for precise timing operations. Designed with expansion and flexibility in mind, the Nucleo-64 board features an ARDUINO® Uno V3 expansion connector and ST morpho extension pin

headers, granting complete access to the STM32's I/Os for comprehensive project integration. Power supply options are adaptable, supporting ST-LINK USB VBUS or external power sources, ensuring adaptability in various development environments. The board also has an on-board ST-LINK debugger/programmer with USB re-enumeration capability, simplifying the programming and debugging process. Moreover, the board is designed to simplify advanced development with its external SMPS for efficient Vcore logic supply, support for USB Device full speed or USB SNK/UFP full speed, and built-in cryptographic features, enhancing both the power efficiency and security of projects. Additional connectivity is

provided through dedicated connectors for external SMPS experimentation, a USB connector for the ST-LINK, and a MIPI® debug connector, expanding the possibilities for hardware interfacing and experimentation. Developers will find extensive support through comprehensive free software libraries and examples, courtesy of the STM32Cube MCU Package. This, combined with compatibility with a wide array of Integrated Development Environments (IDEs), including IAR Embedded Workbench®, MDK-ARM, and STM32CubeIDE, ensures a smooth and efficient development experience, allowing users to fully leverage the capabilities of the Nucleo-64 board in their projects.