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 Abs2Qep Theory of Operation

Figure 4-2 Absolute Position Encoder

An absolute encoder output represents the exact position of a rotating shaft. If Qmax is the resolution of a single rotation, then the position will range from 0 to Qmax. Resolutions in the range Q17 = 217 or Q20 = 2 20 are common. The absolute position increases when the direction is forward (clockwise) and decreases when the direction is reverse (counter-clockwise).

Figure 4-3 Incremental Position Encoder

An incremental encoder output is a quadrature encoder pulse (QEP). This pulse train consists of the following outputs: QEP-A, QEP-B and QEP-I with the following characteristics:

  • The phase between QEP-A and QEP-B indicates the direction of movement. If QEP-A leads by 90°, then the direction is forward (clockwise). If QEP-A lags by 90° degrees, then the direction is reverse (counter-clockwise).
  • The QEP-A/B frequency is proportional to the disk's velocity.
  • The index signal, QEP-I, indicates crossing over absolute zero.

The resolution of the incremental encoder is specified by the number of lines around the disk. As each line passes a sensor, an edge (falling or rising) is generated on QEP-A as shown in Figure 4-3. A second channel can be added by second ring of lines, inside and offset from the outer ring. In such a case, this inner ring of lines generates QEP-B. For example, a 1024 line encoder would have 1024 QEP-A lines and 1024 QEP-B lines for a total of 2048 QEP state changes in a full rotation.

In Abs2Qep, a configurable parameter in the header file defines how many QEP state transitions are generated per line. The QEP state transition is controlled by an internal CLB signal called QCLK as shown in Figure 4-3. The default setting is each line corresponds to two QCLK pulses.

The example in Table 4-1 further clarifies this point.

Table 4-1 Abs2Qep Relationship Between Lines and QCLK (Forward Direction)
Line QCLK QEP-A QEP-B
Line 1 Outer Ring QCLK 1 Rising Edge
Line 1 Inner Ring QCLK 2 Rising Edge
Line 2 Outer Ring QCLK 3 Falling Edge
Line 2 Inner Ring QCLK 4 Falling Edge