Achieve pixel perfection with SZ420757N and STM32F302VC

7x10 R Click is based on two SZ420757N, red LED dot matrix modules from Wuxi Ark. A single LED matrix module is composed of 35 LED elements grouped in rows and columns. The LED elements in one row have their cathodes connected and routed to a single-row pin. The LED elements in one column have their anodes connected and routed to a single-column pin. Multiplexed like this, modules have a fairly low number of pins (12 per module), making them suitable to be driven by shift registers and a decade of counter ICs. The driver circuit consists of two 74HC595 - 8bit, serial input - parallel output shift registers, one CD4017 - a Jonson topology decade counter with ten outputs, and one ULN2003A - an IC with seven integrated Darlington transistor pairs, all

chips produced by Texas Instruments. The shift registers are used to polarize the anodes on the columns of the LED displays. To complete the LED's current path, their cathodes must be connected to the ground. This is where the CD4017 and ULN2003 ICs are used. The ULN2003 IC drives rows of the dot matrix displays by sinking the current on the active row. To activate one of the seven input channels of the ULN2003 IC, the CD4017 decade counter IC is used. The design of the decade counter allows only one row to be active at a time. So, to see the complete picture on an LED matrix, the row scanning has to be fast enough so that the effect called persistent vision takes place. It produces an illusion of a complete image, even if only one row is seen at a time -

because the human eye cannot detect very fast changes in light. 7x10 R Click uses a 4-Wire SPI serial interface of the 74HC595 shift registers to communicate with the host MCU. The shift registers are chained together and can be reset over the RST pin. The clock and the reset inputs of the CD4017 are controlled by the RC and RR pins. This Click board™ can operate with either 3.3V or 5V logic voltage levels selected via the PWR SEL jumper. This way, both 3.3V and 5V capable MCUs can use the communication lines properly. Also, this Click board™ comes equipped with a library containing easy-to-use functions and an example code that can be used as a reference for further development.

Clicker 4 for STM32F3 is a compact development board designed as a complete solution, you can use it to quickly build your own gadgets with unique functionalities. Featuring a STM32F302VCT6, four mikroBUS™ sockets for Click boards™ connectivity, power managment, and more, it represents a perfect solution for the rapid development of many different types of applications. At its core, there is a STM32F302VCT6 MCU, a powerful microcontroller by STMicroelectronics, based on the high-

performance Arm® Cortex®-M4 32-bit processor core operating at up to 168 MHz frequency. It provides sufficient processing power for the most demanding tasks, allowing Clicker 4 to adapt to any specific application requirements. Besides two 1x20 pin headers, four improved mikroBUS™ sockets represent the most distinctive connectivity feature, allowing access to a huge base of Click boards™, growing on a daily basis. Each section of Clicker 4 is clearly marked, offering an intuitive and clean interface. This makes working with the development

board much simpler and thus, faster. The usability of Clicker 4 doesn’t end with its ability to accelerate the prototyping and application development stages: it is designed as a complete solution which can be implemented directly into any project, with no additional hardware modifications required. Four mounting holes [4.2mm/0.165”] at all four corners allow simple installation by using mounting screws. For most applications, a nice stylish casing is all that is needed to turn the Clicker 4 development board into a fully functional, custom design.