MIKROE Servo Click is a compact add-on board that contains a PWM servo driver with voltage sensing circuitry. This board features the PCA9685, an integrated 12-bit, 16-channel PWM driver, which can be configured to either sink 25mA per channel or drive each channel sourcing up to 10mA from NXP. It can be used to simultaneously control 16 servo motors, each with its own programmable PWM signal. The frequency of the control PWM signal can be programmed in the range from 24 Hz to 1526 Hz, which is an ideal range for driving various types of servos. This Click board™ represents a powerful servo controller, especially useful when a large number of servos needs to be easily controlled in the movie or theater industry (animatronics), robotics, RC toys, and similar.

Servo Click is based on the PCA9685, an integrated 12-bit 16-channel PWM driver which can be configured to either sink 25mA per channel or drive each channel sourcing up to 10mA from NXP. Each channel has its duty cycle independently set from 0% to 100%. Offering 16 independent channels, each with its own PWM duty cycle and current sensing ability, this Click board™ represents a powerful servo controller, especially useful when a large number of servos needs to be controlled simply and easily. The frequency of the control PWM signal can be programmed in the range from 24 Hz to 1526 Hz.

The servo can be connected to any of the sixteen headers located on this Click board™. The output signal frequency is determined by the Prescaler value, which is written to the appropriate register. The output channels can be set either in the open-drain or in the push-pull configuration. In the first case, they will be able to sink up to 25mA from up to 5V power supply, while in the second case, they will be able to both drive with up to 10mA or sink up to 25mA.

This Click board™ also has an accurate 16bit A/D converter the LTC2497 from Analog Devices used to sample the voltage drop across the shunt resistor on each of the 16 channels giving feedback on the servo current consumption. The ADC uses an accurate reference of 2.048V provided by an onboard reference voltage regulator MAX6106 from Maxim Integrated. An extremely low noise of this ADC coupled with a low reference voltage allows small voltage drops across the shunt resistor to be accurately converted.

Servo Click communicates with MCU using the standard I2C 2-Wire interface with a frequency up to 100kHz in the Standard, up to 400 kHz in the Fast, and up to 1MHz in the Fast-Plus mode. There are two more SMD jumpers, labeled as the PWM and ADC, located at the bottom of the Click board™ that allows selection of the peripheral I2C address for each of the two onboard ICs. It also has an external connector that can provide more power for servos that operate with heavier loads. That's why the SMD jumper labeled as VCC MOT should be at the EXT position. In this case, an external PSU that can provide more current can be used.

The PCA9685 also offers Output Enable pin, routed to the mikroBUS™ CS pin, labeled as the OE. A LOW logic level on this pin will set all the outputs to the predefined logic state, turning the PWM generators OFF. This may either leave the servo into the fixed position or turn it down completely, depending on the servo model.

This Click board™ is designed to be operated with both 3.3V and 5V logic voltage levels that can be selected via VCC SEL jumper. This allows for both 3.3V and 5V capable MCUs to use the I2C communication lines properly.

• Interface: I²C
• Compatibility: mikroBUS™
• Dimensions: 57.15 x 25.4mm
• Input Voltage: 3.3V or 5V
• Supply Voltage: Min. -0.5V, Max. 6V
• High Level Output Current: Min. -10μA, Max. +10μA
• Low Level Output Current: Min. 12mA, Typ. 25mA
• Total Power Dissipation: 400mW
• Operating Temperature Range: -40°C to +85°C

• Schematic
• LTC2497 Datasheet
• MAX6106 Datasheet
• PCA9685 Datasheet
• mikroSDK
• GitHub