Stepper 6 Click Board™

Product Code: MIKROE-3214

The DRV8886 step motor driver IC can deliver a reasonably high amount of current to the connected load. This IC uses a set of I/O pins, simplifying the control over the connected step motor. Since the DRV8886 IC offers so many options, an additional port expander IC is used to cover them all, offering the full control over the IC via the SPI interface, with no restrictions. The DRV8886 IC also features a full set of protection features: overvoltage, thermal, overcurrent, and undervoltage protection schemes are all present on this IC, along with the fault indication pin. All these features make the Stepper 6 click a robust and versatile bipolar step motor driving solution. With its integrated current sensing, a microstepping ratio up to 1:16, a non-circular stepping mode for higher torque output, a high efficiency, and a reasonably high current it can deliver, the Stepper 6 click is a perfect solution for any application that requires an efficient and reliable motor driver. It can be used in 3D printers, laser printers, laser engravers, video security cameras, factory automatization, robotics, and other similar applications.

How Does The Stepper 6 Click Board™ Work? The Stepper 6 Click Board™ is equipped with the DRV8886, a highly integrated bipolar step motor driver with current sensing, from Texas Instruments. This integrated driver offers a simple interface, featuring a set of pins used to control the functions of the step motor. Since the number of pins exceeds the available mikroBUS™ general purpose pins, an additional port expander IC is used, exposing a 2-wire I2C interface for the communication with the host MCU. The port expander IC is the PCA9538, an 8-bit port expander with the I2C interface, an interrupt, and a reset, from NXP. The high efficiency of the integrated N-Channel power MOSFET H-Bridges allows a high efficiency to be achieved: Stepper 6 click can withstand peaks of current up to 3A, while the internal current limiter is set to 1.4 A per bridge. The Click board™ can work with in the range from 8V up to 35V. However, when operated near the upper current and voltage limits, component heating is expected. If the temperature threshold of 150° is reached, a thermal protection will be engaged, while the fault condition will be indicated with the nFAULT pin of the DRV8886 IC. The nFAULT pin is routed to the port expander IC, allowing its state to be read over the I2C interface. The I2C interface bus of the PCA9538 is routed to the appropriate mikroBUS™ pins (SCA, SDL), allowing the host MCU to control it and read states of its pins. The PCA9538 is also connected to some other pins: both M0 and M1 pins are routed to this IC, allowing the microstepping configuration over the I2C interface. These two pins are used to set the microstepping size in the range from 1 to 1/6 of a step. The current through the coils is indexed and depends on a position, so the angle of 0° will allow 100% of the current to run through the coil, scaling it down to 0% for the 90°. These current values change with the step position and the microstepping current on an H-Bridge output is a sine function. An additional non-circular half-stepping mode is also available when more torque is required at higher motor RPM. The current in this mode is simply switched from 0% to 100% with no indexed values in between. One of the key features of the DRV8886 IC is the integration of the sensing resistors, which reduces the design complexity. The current decay through the coil for the circular microstepping modes is controlled by the DRV8886 IC, which offers three different decaying modes: slow decay, slow-mixed decay, and all mixed decay. The correct decay mode is necessary to prevent loss of the current regulation through the coil which might degrade the efficiency of the stepper motor control. The DECAY pin offers the control over the decay mode, and it is routed to the SMD jumper JP3, allowing it to be either pulled up (to the DVDD) or to the GND. The DRV8886 offers detailed information about the decay modes and how to set this pin for each. The maximum current is limited by setting the current through the RREF pin. A DAC converter is used to set the voltage at this pin. The pin is typically used with the resistor connected to the GND, but the Stepper 6 click uses the MCP4921, a dedicated 12-bit DAC with SPI interface, from Microchip. This way, it is possible to change the maximum current limit by the firmware. The SPI interface of the MCP4921 is routed to the mikroBUS™, allowing the host MCU to take control over the maximum current limit. To find about the current limiting by using the DAC, please visit the DRV8886 datasheet. It offers all the necessary formulas to calculate the required DAC value for a certain current limit. However, the Stepper 6 Click Board™ comes with the library that contains functions which allow operational parameters of the Click board™ to be forwarded as the simple function arguments. The maximum