Maximize efficiency in circuit calibration and tuning with AD5231 and STM32L496AG

DIGI POT 3 Click is based on the AD5231, a 1024-position (10bit) digital potentiometer with a non-volatile memory (EEMEM) from Analog Devices. As mentioned, this digital potentiometer has many features, making it a superior choice over classic mechanical potentiometers. It offers solid state reliability, high precision, additional storage of non-volatile (NV) memory cells, and, most importantly - it can be digitally controlled by an MCU via the high-speed SPI interface, with its pins routed to the mikroBUS™. Analog Devices Inc. offers several sub-types of the same IC, but the DIGI POT 3 click uses the one labeled AD5231BRUZ10, meaning it has 10KΩ of resistance between the potentiometer endpoints. One of its distinctive features is to refresh its wiper register (called RDAC in the device datasheet) after the power is on, making it possible to restore the wiper position on power-up, just like the mechanical counterpart. The wiper position register (RDAC) is not automatically written to the EEMEM because this type of memory has a limited number of write cycles, which is the limitation of the technology itself. For this reason, once the position has been established, it can be stored in EEMEM by a command (Command 0x2 - Store RDAC setting to EEMEM). The AD5231 IC is factory pre-programmed to set the wiper at the middle position after the power-on, but this can be overwritten by storing a custom position with the command mentioned above. Besides storing the RDAC register to the EEMEM, it is possible to store 14 more words, each 16 bits long. This EEMEM area can be used for any purpose - lookup tables, data for other components, or system identification information. Writing to EEMEM takes some time, and the AD5231 IC is non-

responsive. This time is about 25ms, and the end of this operation is signaled by the RDY pin of the AD5231 IC, routed to the INT pin of the mikroBUS™ - labeled as the RDY. When the read-to or write from the EEMEM cycle is done, this pin pulses to a LOW logic level. It is otherwise pulled to a HIGH logic level by an onboard pull-up resistor. For the complete list of commands and addresses, please refer to the AD5231 datasheet. However, MikroElektronika provides a library containing functions compatible with the MIKROE compilers, which can be used for simplified DIGI POT 3 Click programming. The library also contains an example application that demonstrates its use. This example application can be used as a reference for custom designs. The Click board™ is equipped with edge screw terminals, which connect the Click board™ to the external electrical circuit. They offer a secure connection to the external electrical circuit. A small print of a potentiometer electrical symbol illustrates how to connect these terminals properly: Inputs labeled as A and B are the endpoints of the digital potentiometer, while W is the wiper. Lastly, the GND symbol connects the circuit's ground where the potentiometer will be used. DIGI POT 3 Click allows using of both unipolar and bipolar signals. The potential across the positive and the negative power supply pins define the boundary conditions for a proper digital potentiometer operation. The internal forward-biased diodes clamp supply signals on the A, B, and W terminals that exceed this range. Since this Click board™ is intended to be used on the mikroBUS™, the power supply voltage of the AD5231 is +3.3V or +5V, selectable by an onboard SMD jumper labeled as VCC SEL. This makes working with the voltage range between 0

and VCC possible. By utilizing additional circuitry, it is also possible to work with the bipolar signals, which can be useful for interfacing the digit to an audio source. Since no negative power supplies are available on the mikroBUS™, the Click board™ uses the MCP6022, a rail-to-rail, 10 MHz onboard operational amplifier from Microchip, to support operation with bipolar signals. It is a non-inverting amplifier with a unity gain - a buffer. Several onboard SMD jumpers are used to route the signal so it passes through the buffer instead of being fed directly to the AD5231 IC. A group of SMD jumpers labeled as SIGNAL POLARITY is used to patch the signal to a proper route: setting all these jumpers to the LEFT position will connect the terminal inputs directly to the AD5231 IC, allowing unipolar signals ranging from 0 to VCC to be connected. Moving all these jumpers to the RIGHT position will route the input signal through the decoupling capacitor and the buffer, allowing bipolar signals to be used and introducing an offset of VCC/2. This allows the signal to swing between VCC/2 and GND for the negative half-cycle and between VCC/2 and VCC for the positive half-cycle. The offset is then removed by a decoupling capacitor at the W terminal. The SMD jumpers should be moved to the LEFT or the RIGHT position, as leaving some of them in the opposite position may render the device unresponsive. The AN pin can be used as an auxiliary wiper output if routing of the wiper back to the mikroBUS™ is required. This pin can be completely disconnected from the mikroBUS™ by moving the appropriate SMD jumper labeled as AN to the RIGHT position. This will not affect the presence of the wiper output on the output terminal.

The 32L496GDISCOVERY Discovery kit serves as a comprehensive demonstration and development platform for the STM32L496AG microcontroller, featuring an Arm® Cortex®-M4 core. Designed for applications that demand a balance of high performance, advanced graphics, and ultra-low power consumption, this kit enables seamless prototyping for a wide range of embedded solutions. With its innovative energy-efficient

architecture, the STM32L496AG integrates extended RAM and the Chrom-ART Accelerator, enhancing graphics performance while maintaining low power consumption. This makes the kit particularly well-suited for applications involving audio processing, graphical user interfaces, and real-time data acquisition, where energy efficiency is a key requirement. For ease of development, the board includes an onboard ST-LINK/V2-1

debugger/programmer, providing a seamless out-of-the-box experience for loading, debugging, and testing applications without requiring additional hardware. The combination of low power features, enhanced memory capabilities, and built-in debugging tools makes the 32L496GDISCOVERY kit an ideal choice for prototyping advanced embedded systems with state-of-the-art energy efficiency.