Stepper Step Count

NetBurner SAME70 Stepper Motor Step Count Example

Overview

This example demonstrates an advanced stepper motor control system using the NetBurner SAME70 platform's sophisticated timer coordination capabilities. The application uses three interconnected timer channels to create a complete stepper motor driver with precise step counting, programmable frequency control, and hardware-based pulse generation.

Supported Platforms

• MODM7AE70

Features

• Multi-Timer Coordination: Uses three synchronized timer channels working together
• Precise Step Counting: Tracks and counts individual step pulses with completion detection
  
• Variable Frequency Control: Programmable step rates from low to high frequencies
• Large Step Count Support: Handles step counts up to millions through interrupt-driven management
• Bidirectional Control: Software-controlled direction (up/down counting)
• Hardware-Based Generation: Timer hardware generates consistent pulses independent of CPU load
• Real-Time Command Interface: Interactive serial console for dynamic control
• Advanced Timer Cross-Coupling: Sophisticated timer interconnection for coordinated operation
• Completion Synchronization: Semaphore-based notification when step sequences complete

Hardware Configuration

Pin Assignments

MODM7AE70:**

• P1.8: TIOA8 (Timer channel A output - primary step pulses)
• P2.6: TIOB8 (Timer channel B output - secondary output/direction)

Timer Architecture

Timer Coordination System:
 
   +------------------+    Cross-Trigger    +-------------------+
   | Frequency Timer  |    Connection       | Pin Control Timer |
   | (Timer 6)        |-------------------->| (Timer 8)         |
   | Generates PPS    |                     | Stepper Mode      |
   +------------------+                     | Hardware Pulses   |
            |                               +-------------------+
            | Clock Signal                            |
            v                                         | Step Pulses
   +------------------+                               v
   | Step Count Timer |                    +-------------------+
   | (Timer 7)        |                    | Stepper Motor     |
   | Tracks Progress  |                    | Controller        |
   | Interrupt-Driven |                    | Hardware          |
   +------------------+                    +-------------------+

Timer Channel Assignments

• Timer 6 (TIMER_STEP_FREQ): Frequency generation and base timing
• Timer 7 (TIMER_STEP_COUNTER): Step count management and completion tracking
• Timer 8 (TIMER_STEP_PINS): Hardware pulse generation and stepper mode control

Application Flow

System Startup
      |
      v
Initialize Hardware
      |
      v
Configure Pin Functions
      |
      v
Allocate Timer Resources
      |
      v
Setup Timer Cross-Coupling
      |
      v
Main Command Loop
      |
      v
  +-------------------------+
  | User Command Input      |
  | <steps>,<rate>,<dir>    |
  +-------------------------+
      |
      v
Parse and Validate Command
      |
      v
Configure Timer Parameters
      |
      v
  +----------+----------+
  |          |          |
  v          v          v
Frequency  Count      Pin
Timer      Timer      Timer
Setup      Setup      Setup
  |          |          |
  +----------+----------+
      |
      v
Synchronized Timer Start
      |
      v
Hardware Pulse Generation
      |
      v
Interrupt-Driven Counting
      |
      v
Wait for Completion Signal
      |
      v
Display Results
      |
      v
Return to Command Loop

User Interface

The application provides an interactive command-line interface for real-time stepper motor control.

Command Format

<step count>,<steps per second>,<U/D>

Parameters:**

• step count: Total number of steps to execute (positive integer)
• steps per second: Step frequency/rate (positive integer)
• direction: 'U' or 'u' for up counting, 'D' or 'd' for down counting

Usage Examples

> 3000,300,D
    Execute 3000 steps at 300 steps per second, counting down
 
> 30000,2000,U
    Execute 30000 steps at 2000 steps per second, counting up
 
> 500000,1000,D  
    Execute 500000 steps at 1000 steps per second, counting down

Operation Sequence

1. System prompts with >
2. User enters command in specified format
3. System validates input parameters
4. If valid, stepper sequence begins immediately
5. System waits for completion (blocking operation)
6. Upon completion, displays actual step count achieved
7. Returns to prompt for next command

Key Technical Features

Multi-Timer Coordination

The application implements a sophisticated three-timer coordination system:

Timer Interconnection:**

• Frequency timer generates the base clock signal
• Pin timer receives frequency timer output via cross-coupling
• Count timer tracks step progression using interrupt callbacks
• All timers operate from the same timer block for proper cross-coupling

Large Step Count Support

Handles step counts beyond 16-bit timer limitations through intelligent phase management:

Step Count Phases:**

• Phase 1 (< 65,536 steps): Direct single-timer configuration
• Phase 2 (65,536 - 69,631 steps): Two-phase interrupt management
• Phase 3 (> 69,631 steps): Multi-phase interrupt-driven counting

Clock Source Optimization

Automatically selects optimal clock source for requested frequency:

Available Clock Sources:**

• PCK6 (Programmable Clock 6)
• PERIPH_CLOCK/8
• PERIPH_CLOCK/32
• PERIPH_CLOCK/128

Selection algorithm minimizes frequency error for best timing accuracy.

Hardware Stepper Mode

Timer 8 operates in dedicated stepper mode providing:

• Automatic step/direction signal generation
• Hardware-controlled pulse width and timing
• Gray code sequence generation
• Direction control via software commands

Important Notes

Hardware Requirements

• All three timer channels (6, 7, 8) must be from the same timer block
• Timer cross-coupling requires specific timer block architecture
  
• Pin functions must be properly configured for timer outputs

Platform-Specific Considerations

• MODM7AE70: Uses Timer Block 2 (channels 6, 7, 8)
• Pin Conflicts: Some pins may conflict with other peripheral functions
• Clock Configuration: PCK6 requires proper system clock setup

Operational Characteristics

• Timing Precision: Hardware timers provide microsecond-level accuracy
• CPU Independence: Once started, pulse generation continues without CPU intervention
• Interrupt Overhead: Step counting uses low-priority interrupts for minimal system impact
• Completion Detection: Semaphore-based synchronization ensures reliable completion notification

Limitations and Considerations

• Maximum practical step frequency limited by timer clock sources
• Very high step counts may take significant time to complete
• Command interface blocks until step sequence completion
• Timer resource allocation must succeed for proper operation

Application Areas

This example is particularly valuable for:

Industrial Applications

• CNC machine tool control systems
• Automated manufacturing equipment
• Precision positioning systems
• Assembly line automation

Robotics Applications

• Multi-axis robot control
• Precision servo positioning
  
• Automated pick-and-place systems
• Mobile robot wheel control