SPRAC77E January   2022  – February 2022 TMS320F28379D , TMS320F28379D-Q1 , TMS320F28379S

 

  1.   Trademarks
  2. 1Introduction
  3. 2PTO – PulseGen
    1. 2.1 PulseGen Implementation Overview
    2. 2.2 PulseGen Limitations
    3. 2.3 PulseGen CLB Configuration
    4. 2.4 PulseGen Input and Output Signals
  4. 3PTO – QepDiv
    1. 3.1 QepDiv Implementation Overview
    2. 3.2 QepDiv Limitations
    3. 3.3 QepDiv Divider Settings and Initialization
    4. 3.4 QepDiv CLB Configuration
  5. 4PTO – Abs2Qep
    1. 4.1 Abs2Qep Chip resources
    2. 4.2 Abs2Qep Theory of Operation
      1. 4.2.1 Abs2Qep Translation Equations
      2. 4.2.2 Abs2Qep Translation Example
      3. 4.2.3 Abs2Qep Zero Cross Detection
    3. 4.3 Abs2Qep CLB Configuration
      1. 4.3.1 Abs2Qep QEP-A/B Pulse Train Generation
      2. 4.3.2 Abs2Qep Halt Latch
      3. 4.3.3 Abs2Qep High Level Controller (HLC)
    4. 4.4 Abs2Qep Input and Output Signals
  6. 5PTO – QepOnClb QEP Decoder
    1. 5.1 QepOnClb and eQEP Comparison
    2. 5.2 QepOnClb Chip resources
    3. 5.3 QepOnClb Theory of Operation
    4. 5.4 QepOnClb CLB Resources
      1. 5.4.1 QepOnClb QCLK State Machine
      2. 5.4.2 QepOnClb Direction Decode
      3. 5.4.3 QepOnClb Error Detection
      4. 5.4.4 QepOnClb Simulation Waveforms
  7. 6Example Projects
    1. 6.1 Hardware Requirements
    2. 6.2 Installing Code Composer Studio and C2000WARE-MOTORCONTROL-SDK™
    3. 6.3 Import and Run Example Project
    4. 6.4 PulseGen Example
    5. 6.5 QepDiv Example
    6. 6.6 Abs2Qep Example
      1. 6.6.1 Watch Variables
      2. 6.6.2 Test Signals
      3. 6.6.3 Pin Usage and Test Connections
    7. 6.7 QepOnClb Example
      1. 6.7.1 Watch Variables
      2. 6.7.2 Header Pin Connections
  8. 7Library Source and Projects
    1. 7.1 Locating the Library Source Code
    2. 7.2 Import and Build the Library Project
    3. 7.3 PTO - PulseGen API
      1. 7.3.1 pto_pulsegen_runPulseGen
      2. 7.3.2 pto_startOperation
      3. 7.3.3 pto_pulsegen_setupPeriph
      4. 7.3.4 pto_pulsegen_reset
    4. 7.4 PTO - QepDiv API
      1. 7.4.1 pto_qepdiv_config
      2. 7.4.2 pto_startOperation
      3. 7.4.3 pto_qepdiv_setupPeriph
      4. 7.4.4 pto_qepdiv_reset
    5. 7.5 PTO - Abs2Qep API
      1. 7.5.1 Abs2Qep API Configuration
      2. 7.5.2 pto_abs2qep_runPulseGen
      3. 7.5.3 pto_abs2qep_setupPeriph
      4. 7.5.4 pto_abs2qep_translatePosition
    6. 7.6 PTO - QepOnClb API
      1. 7.6.1 pto_qeponclb_setupPeriph
      2. 7.6.2 pto_qeponclb_initCLBQEP
      3. 7.6.3 pto_qeponclb_configMaxCounterPos
      4. 7.6.4 pto_qeponclb_enableCLBQEP
      5. 7.6.5 pto_qeponclb_resetCLBQEP
      6. 7.6.6 pto_qeponclb_getCounterVal
      7. 7.6.7 pto_qeponclb_getCLBQEPPos
      8. 7.6.8 pto_qeponclb_clearFIFOptr
  9. 8Using the Reference APIs in Projects
    1. 8.1 Adding PTO Support to a Project
    2. 8.2 Routing To and From the CLB
    3. 8.3 Initialization Steps
      1. 8.3.1 PTO-PulseGen API Initalization
      2. 8.3.2 PTO-QepDiv API Initialization
      3. 8.3.3 PTO-Abs2Qep API Initialization
      4. 8.3.4 PTO-QepOnClb API Initialization
  10. 9References
  11.   Revision History

4.2.1 Abs2Qep Translation Equations

All of the Abs2Qep translation calculations are handled by the C28x. Based on the results, the CLB tile is then configured to generate the specific QEP signals. The CLB configuration is detailed in Section 4.3.

Note: The parameters used in the translation equations are configurable in the Abs2Qep library header file. This includes: absolute encoder resolution, incremental encoder lines per revolution, drive maximum revolutions per minute.

The Abs2Qep translation uses the ratio ABS_TO_INCR to map a change in absolute position to a corresponding number of QEP edges. Any fraction of an edge is tracked. If the fractional edge accumulation reaches 1, then an additional edge is generated.

Equation 1. ABS_TO_INCR = QCLK_PER_LINE x LINES_PER_REV ABS_MAX_POSITION = QCLK_PER_REVOLUTION ABS_MAX_POSITION

where

  • LINES_PER_REV is the incremental encoder resolution.
  • QCLK_PER_LINE is typically 2. One for QEP-A and one for QEP-B.
  • ABS_MAX_POSITION = 2ABS_ENCODER_RESOLUTION. For example 220.

The number of QCLKs, or QEP edges, that represent a change in position is:

Equation 2. QCLK = ABS_TO_INCR x DELTA_ABS_POSITION

where:

  • DELTA_ABS_POSITION = ABS_POSITION(n) - ABS_POSITION(n-1) the change in absolute position between the current sample (n) and the previous sample (n-1).
  • QCLK is the total number of QEP-A + QEP-B edges required to represent the change in position.
Note: This simple translation in Equation 2 assumes absolute zero was not crossed. For zero-cross detection, see Section 4.2.3

For a given position change, the frequency of QCLK is such that the edges are equally divided across the position sampling period. This frequency is expressed in terms of CLB clock cycles.