Introduction

Position and Speed Measurement Using eQEP

This example provides position and speed measurement using the capture unit and speed measurement using unit time out of the eQEP module. ePWM and a GPIO are configured to generate simulated eQEP signals. The ePWM module will interrupt once every period and call the position/speed calculation function. This example uses the IQMath library to simplify high-precision calculations.

Figure 1a. Block diagram

The configuration for this example is as follows

Maximum speed is configured to 6000rpm (baseRPM)
Minimum speed is assumed at 10rpm for capture pre-scalar selection
Pole pair is configured to 2 (polePairs)
Encoder resolution is configured to 4000 counts/revolution (mechScaler)
Which means: 4000 / 4 = 1000 line/revolution quadrature encoder (simulated by ePWM)
ePWM (simulating QEP encoder signals) is configured for a 5kHz frequency or 300 rpm (= 4 * 5000 cnts/sec * 60 sec/min) / 4000 cnts/rev)

SPEEDRPM_FR: High Speed Measurement is obtained by counting the QEP input pulses for 10ms (unit timer set to 100Hz).

SPEEDRPM_FR = (Position Delta / 10ms) * 60 rpm

SPEEDRPM_PR: Low Speed Measurement is obtained by measuring time period of QEP edges. Time measurement is averaged over 64 edges for better results and the capture unit performs the time measurement using pre-scaled SYSCLK.

Note that the pre-scaler for capture unit clock is selected such that the capture timer does not overflow at the required minimum frequency.

This example waits for 10 iterations of unit time out event and verifies the measured speed: 295 < posSpeed.speedRPMFR < 305

posSpeed.speedRPMFR - Speed meas. in rpm using QEP position counter
posSpeed.speedRPMPR - Speed meas. in rpm using capture unit
posSpeed.thetaMech - Motor mechanical angle (Q15)
posSpeed.thetaElec - Motor electrical angle (Q15)

External connections

Connect ePWM0A to eQEP0A (EPWM_A simulates eQEP Phase A signal)
Connect ePWM0B to eQEP0B (EPWM_B simulates eQEP Phase B signal)
Connect GPIO48 to eQEP0I (GPIO simulates eQEP Index Signal)

AM263X-CC or AM263PX-CC

When using AM263x-CC with TMDSHSECDOCK (HSEC180 controlCARD Baseboard Docking Station)

Connect HSEC Pin 49 (ePWM0A) to HSEC Pin 102 (eQEP0A)
Connect HSEC Pin 51 (ePWM0B) to HSEC Pin 100 (eQEP0B)
Connect HSEC Pin 52 (GPIO48) to HSEC Pin 106 (eQEP0I)

AM263X-LP or AM263PX-LP

Connect J2 Pin 11 (ePWM0A) to J25 Pin 1 (eQEP2A)
Connect J6 Pin 59 (ePWM0B) to J25 Pin 2 (eQEP2B)
Connect J2 Pin 40 (GPIO48) to J25 Pin 3 (eQEP2I)

Supported Combinations

Parameter	Value
CPU + OS	r5fss0-0 nortos
Toolchain	ti-arm-clang
Boards	am263x-cc, am263x-lp
Example folder	examples/drivers/eqep/eqep_position_speed/

Steps to Run the Example

When using CCS projects to build, import the CCS project for the required combination and build it using the CCS project menu (see Using SDK with CCS Projects).
When using makefiles to build, note the required combination and build using make command (see Using SDK with Makefiles)
Establish connections as mentioned in External Connections section
Launch a CCS debug session and run the executable, see CCS Launch, Load and Run
View the UART console logs for results

Sample Output

Shown below is a sample output when the application is run,

EQEP Position Speed Test Started ...
Please ensure EPWM to EQEP loopback is connected...
Please wait few seconds ...
Expected speed = 300 RPM, Measured speed = 299 RPM
Electrical angle (Q15) = 19608
Mechanical angle (Q15) = 26188
Rotation direction = CW, forward
EQEP Position Speed Test Passed!!
All tests have passed!!

Table of Contents