This repository contains sourcefiles and schematics for a DRV8825 based
dual stepper driver board. The stepper control algorithm is implemented
on an ATMega328P. The code is compatible with avr-gcc (see Makefile) and
the Arduino IDE (one has to #define ARDUINO 1 to use code for the
Arduino platform).
This controller is thought to be used in robotic and CNC applications. Some features make it useable as cruise control controller for small robots that use steppers instead of other brushed or brushless motors and which may require precise control over speed / sometimes precise control over their position.
Since the controller uses I2C it can be controlled from 3.3V and 5V devices without any level shifters (if pullups are only present to 3.3V but not 5V vcc).
The controller is currently work in progress (but usable). Functions that have been tested won't change behaviour
Correctness proof is currently work in progress
The stepper driver can be controlled via I2C and supports:
- Running at a constant speed
- Accelerated linear movement from one position to another position (stop to stop) as needed in many CNC applications
- Hold position (enable drivers, no movement)
- Free-wheeling (disable drivers)
- Accelerating or decelerating to another speed
- Emergency stop / Emergency stop with hold
Additional features:
-
Commands and status via I2C to support up to 127 stepper driver boards (i.e. up to 254 steppers) per I2C bus.
-
Runtime modification of acceleration/deceleration as well as maximum speed.
-
Runtime reconfiguration of microstepping
-
A configurable depth command queue (default 10 commands per channel)
-
Aborting running commands
-
Keeping track of current position (if enabled - useful for CNC applications)
-
Keeping track of current speed
-
Static analysis using frama-c and ACSL annotation is used to proof that the code is free of many known common runtime errors, numeric overflows/underflows, does only access valid memory, etc. and fulfills some properties (proofed by using an proof assistant). This is currently work in progress.
| Command | Implemented | Tested | Description | Comments |
|---|---|---|---|---|
| Group 0: Configuration | ||||
| i2cCmd_GetAccelerateDecelerate | Y | Y | 8 byte payload Slave -> Master + 1 Byte Status | |
| i2cCmd_SetAccelerateDecelerate | Y | 8 Byte payload Master -> Slave | ||
| i2cCmd_GetVMax | Y | 4 byte payload Slave -> Master + 1 Byte Status | ||
| i2cCmd_SetVMax | Y | 4 Byte payload Mater -> Slave | ||
| i2cCmd_GetAlpha | Y | 4 Byte payload Slave -> Master + 1 Byte Status | ||
| i2cCmd_SetAlpha | Y | 4 Byte payload Master -> Slave | ||
| i2cCmd_GetMicrostepping | Y | 1 Byte payload Slave -> Master (2x 3 Bit) + 1 Byte Status | ||
| i2cCmd_SetMicrostepping | Y | Y | 1 Byte payload Master -> Slave | Note: Currently microstepping does not rescale step size (alpha) automatically |
| i2cCmd_GetFault | Y | 1 Byte payload Master -> Slave (IS status) | ||
| i2cCmd_RecalculateConstants | Y | Used to trigger recalculation of all constants (expensive operation; system should be stopped) | ||
| Group 1: Queue | ||||
| i2cCmd_GetCommandQueueSize | Y | Get size (first byte) and unused entires (second byte) of command queue + 1 Byte status | ||
| Group 2: Enqueue commands | ||||
| i2cCmd_Queue_Sync | Sync. point; 1 Byte Channel | |||
| i2cCmd_Queue_ConstSpeed | Y | Y | Constant speed; 1 Byte Channel; 4 Byte Speed | |
| i2cCmd_Queue_MoveTo | Y | Y | Move To (accelerated); 1 Byte Channel; 4 Byte Position | |
| i2cCmd_Queue_ConstSpeedAccel | Y | Y | Constant speed with acceleration/deceleration; 1 Byte channel; 4 Byte speed | |
| i2cCmd_Queue_Hold | Y | Y | Hold position; 1 byte channel | |
| i2cCmd_Queue_DisableDrv | Y | Y | Disable drivers; 1 byte channel (both have to be ordered to disable to be effective) | |
| Group 3: Execute commands immedately | ||||
| i2cCmd_Exec_Sync | Sync. point; 1 Byte Channel | |||
| i2cCmd_Exec_ConstSpeed | Y | Y | Constant speed; 1 Byte Channel; 4 Byte Speed | |
| i2cCmd_Exec_MoveTo | Y | Y | Move To (accelerated); 1 Byte Channel; 4 Byte Position | |
| i2cCmd_Exec_ConstSpeedAccel | Y | Y | Constant speed with acceleration/deceleration; 1 Byte channel; 4 Byte speed | |
| i2cCmd_Exec_Hold | Y | Y | Hold position; 1 byte channel | |
| i2cCmd_Exec_DisableDrv | Y | Y | Disable drivers; 1 byte channel (both have to be ordered to disable to be effective) | |
| Group F: Emergency commands | ||||
| i2cCmd_EmergencyStop | Y | Keeps motors engaged but stopped | Drivers stay engaged so current will keep flowing | |
| i2cCmd_EmergencyOff | Y | Keeps motors disabled | Since drivers are disabled motors are free to turn freely (inertia!) |
The host library (controller) has been currenty implemented and tested
on FreeBSD (especially on the RaspberryPi platform). Example usage can
be seen in the controller/tests directory.