2-Axis Stepper Motor Controller Wing
This is a microstepping single axis stepper motor controller based on Texas Instruments DRV8821 device. It is intended to be used with the S3E Cocoon. It can drive two bipolar stepper motors rated upto 27V and 1.5A, with a simple parallel command interface. The Wing uses a 16-bit Butterfly segment.
Following the DRV8821 documentation, the two motor drivers are referred to as AB and CD respectively.
Direction is from the perspective of the FPGA or microcontroller.
Using 2-Axis Stepper Motor Controller Wing
This Wing uses a 16-bit segment on a Butterfly Cocoon, like the S3E FPGA Cocoon. Following the DRV8821 documentation, the two motor drivers are referred to as AB and CD respectively.
The board has ample copper area for heat dissipation from the tiny DRV8821 device, with thermal vias on the underside of the chip to transfer heat from the exposed thermal pad.
1. Use 'IOV Select' jumper to select logic IO voltage between 5V or 3.3V that depends on the host device or the Cocoon.
2. Microstep selection inputs ABUSM0/ABUSM1, CDUSM0/CDUSM1 can be set from your host i.e. the S3E FPGA pins to appropriate value.
3. The logic inputs nABRESET, nCDRESET, nEN_AB, nEN_CD, ABUSM0, ABUSM1, CDUSM0, CDUSM1, ABDIR, CDDIR do not have any built-in pullup/pulldown resistors. They must be externally set to their active values.
4. Phoenix connectors (terminal blocks) are used for easy integration of power sources and stepper motors.
5. Variable resistor R5 are R6 are used to set the current limit by setting the voltage that can be measured on the pad adjacent to the potentiometer. R6 sets reference voltage VREF_AB for motor AB and R5 sets reference voltage VREF_CD for motor CD.
A small table for reference voltage values for certain values of current limit is printed on the top silkscreen. Start with the lowest possible value and increase it gradually till you get adequate torque output from the motor.
Operational Limits and Precautions
While this controller Wing can be operated by discrete IO signals from the FPGA or a microcontroller, a special peripheral core for the FPGA is being developed that will take care of applying timed pulses to the controller and also manage acceleration, deceleration and direction control through simple register interface. Please check the Stepper Controller Peripheral core project page.
The 2-Axis Stepper Motor Controller Wing PCB's are currently being built and tested. Look for this item to be available in the store in the next couple of weeks.