Empower creativity and transform ideas into stunning visuals using IS31FL3731 and STM32F103RB

16x9 G Click is based on the IS31FL3731, a LED array driver from ISSI. This device uses the cross-plexing technology which allows it to drive a large number of LED segments (144) with a small number of I/O pins. The IC has 28 pins in total, but it has two matrices with only 9 pins each for LED driving - which makes it 18 pins in total. It is possible by using the cross-plexing technique, also known as the Charlie-plexing, named by Charlie Allen, an engineer from Maxim Integrated, who made the first practical application example by utilizing this technique, for the company he was working at. The working principle of this technique is based around using Hi-Z pins. This adds the third element for the LED control, unlike the commonly used matrix multiplexing, when two pins can change states to either LOW-HI or HI-LOW, saving only a single pin per cell. A basic cell of the cross-plexed LED matrix consists of three pins and 6 LEDs which is substantially more than the regular matrix. The bigger the matrix is, the higher the efficiency of such multiplexing becomes. N pins are able to drive N2-N LED segments. The IS31FL3731 has some additional features. Besides two banks of driving pins, it can store up to 8 frames in its internal memory. This allows small movies to be autonomously played back by the IC itself, without using the MCU processing power. The device can operate in Picture Mode, in the Auto Frame Mode, and in the Audio Frame Mode. While operating in Picture mode, it will display a

selected frame and can apply a breathing effect to it. Auto Frame Mode will sequence through all the frames. The delay between frames, as well as the transition effect, can be configured by the user. The Auto Frame Mode can also be used as the buffer for playing back more frames, which can be externally loaded to the IC while it plays back its 8 frames buffer. Finally, the Audio Frame Mode allows the audio signal at the IN pin to control the frame rate advancement (lowest signal level will display the first frame, the highest signal level will display the last frame). All the programmable parameters are stored via the I2C to appropriate registers. The datasheet of the IS31FL3731 offers ian n-depth explanation of all the registers. The interrupt engine allows the interrupt event to be generated by pulling the INTB pin to a LOW logic level and setting the appropriate status register bit to 1. INTB pin will report whenever the cycle in the Auto Frame Mode is finished. Every time when the frame sequence is ended, this pin will be pulsed to a LOW logic level, and after 7ms, it will return to a HIGH logic level, automatically. The INT bit signalizing the interrupt will be cleared once the Status Register is read by the host MCU but will not automatically revert to 0. The INTB pin is routed to the mikroBUS™ INT pin. The SDB pin can be used to completely turn off the IC when power saving is a concern. Pulling this pin to a LOW logic level will put the device into the Hardware Shutdown Mode, which powers down

the entire IC. No read or write operations are possible, unlike the Software Shutdown Mode, which is set by a bit in the respective (Shutdown) register. Software shutdown Mode will turn off the drivers and most of the IC, but the communication will be possible. In fact, some registers can be read only in Software Shutdown Mode, such as the Frame registers. The SDB pin is normally pulled to a LOW logic level by the onboard pulldown resistor, so initialization procedure should contain setting this pin to a HIGH logic level. The SDB pin routed to the mikroBUS™ CS pin and it is labeled as SDB. The IN pin of the IS31FL3731 is used to sample the input data and either modulate the LED segment brightness according or advance the playback frame. It is decoupled by a capacitor, accepting the line-level audio signal. On the 16x9 Click board™, this pin is routed to the PWM pin of the mikroBUS™, thus the PWM signal from the MCU can be used instead of the audio signal. Naturally, the device will still react to an audio source, since the PWM signal is just another type of a waveform applied to the IN pin. The PWM pin of the mikroBUS™ is labeled as IN on the Click board™. There are two SMD jumpers on this Click board™. The first SMD jumper is used to select the least significant bit (LSB) of the I2C address, and it is labeled as the ADDR SEL. The second SMD jumper is labeled as the VCC SEL and it is used to set the operating voltage of the device, allowing it to be interfaced with both 3.3V and 5V MCUs.

Nucleo-64 with STM32F103RB 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.