TMS320F28379D: Problem with eQEP

Part Number: TMS320F28379D

Hi all,

I try to run the eQEP for TMS320F28379D and using CCS with the F2837xD driver lib v3.05

After initialization of eQEP I check the position with "EQEP_getPosition" in an endless loop. Additionally I'm using an interrupt handler triggert by eQEP to check the Position Latch with "EQEP_getIndexPositionLatch".

After startup I move the encoder forward and get this:

pos: 0      {moving forward}
pos: 1
pos: 2
...
...
pos: 3998
pos: 3999
*IRQ*       (get position latch 3999)
pos: 0
pos: 1
pos: 2
...
...
pos: 3998
pos: 3999
*IRQ*       (get position latch 3999)
pos: 0
pos: 1
pos: 2
...
...

This looks good. After startup again but moving the encoder backward I get this:

pos: 2      {moving backward}
pos: 1
pos: 0
*IRQ*       (get position latch 0)
pos: 3999
pos: 3998
...
...
pos: 2
pos: 1
pos: 0
*IRQ*       (get position latch 0)
pos: 3999
pos: 3998
...
...

Looks great too. Everything looks fine as long as I moving the encoder in the same direction.

But now the Problem: When I pass the index in different directions I get a problem:

pos: 3995   {moving forward}
pos: 3996
pos: 3997
pos: 3998
pos: 3999
*IRQ*       (get position latch 3999)
pos: 0
pos: 1
pos: 2
pos: 3      {now moving backward}
pos: 2
pos: 1
pos: 0
pos: 3999
pos: 3998
pos: 3997
pos: 3996
*IRQ*       (get position latch 3996 and EQEP_INT_POS_CNT_ERROR)
pos: 3999
pos: 3998
pos: 3997
pos: 3996   {moving forward agian}
pos: 3997
pos: 3998
pos: 3999
pos: 0
pos: 1
pos: 2
*IRQ*       (get position latch 2 and EQEP_INT_POS_CNT_ERROR)
pos: 0
pos: 1
pos: 2
pos: 3
...

when still move forward and pass the index again after 360 deg then everythig OK again:wieder.

...
pos: 3998
pos: 3999
*IRQ*       (get position latch 3999)
pos: 0
pos: 1
pos: 2
...
...

The index interrupt comes to late after changing the direction and I not know why. Mostly the index interrupt comes 3

ticks too late, sometimes 2 ticks and sometimes up to 7 ticks.

To check if I have some hardware issues I configured the /A/B/I pins as normal input pins and print out what happen when

moving the encoder:

A B I
-----
0 0 0
1 0 0
1 1 0
0 0 1
1 0 0
1 1 0
0 1 0
0 0 0

This pattern don't change even if I change the direction.

This is my initialization code (based on a example from driver lib):

SysCtl_enablePeripheral(SYSCTL_PERIPH_CLK_EQEP3);

GPIO_setPadConfig(6, GPIO_PIN_TYPE_STD);
GPIO_setPadConfig(7, GPIO_PIN_TYPE_STD);
GPIO_setPadConfig(9, GPIO_PIN_TYPE_STD);

GPIO_setPinConfig(GPIO_6_EQEP3A);
GPIO_setPinConfig(GPIO_7_EQEP3B);
GPIO_setPinConfig(GPIO_9_EQEP3I);

Interrupt_register(INT_EQEP3, &index_interrupt_handler);
Interrupt_enable(INT_EQEP3);

EQEP_setDecoderConfig(EQEP3_BASE, (EQEP_CONFIG_1X_RESOLUTION |EQEP_CONFIG_QUADRATURE | EQEP_CONFIG_NO_SWAP));
EQEP_setEmulationMode(EQEP3_BASE, EQEP_EMULATIONMODE_RUNFREE);
EQEP_setPositionCounterConfig(EQEP3_BASE, EQEP_POSITION_RESET_IDX, ENCODER_MAX_TICKS - 1);
EQEP_enableUnitTimer(EQEP3_BASE, (f2837x::system::get_cpu_clock_speed() / 100));
EQEP_setLatchMode(EQEP3_BASE, EQEP_LATCH_UNIT_TIME_OUT);
EQEP_enableInterrupt (EQEP3_BASE, EQEP_INT_INDEX_EVNT_LATCH | EQEP_INT_UNDERFLOW | EQEP_INT_OVERFLOW | 

EQEP_INT_POS_CNT_ERROR | EQEP_INT_PHASE_ERROR);
EQEP_enableModule(EQEP3_BASE);
EQEP_setCaptureConfig(EQEP3_BASE, EQEP_CAPTURE_CLK_DIV_64, EQEP_UNIT_POS_EVNT_DIV_32);
EQEP_enableCapture(EQEP3_BASE);

I also tested latch mode EQEP_LATCH_RISING_INDEX and EQEP_LATCH_FALLING_INDEX with same result.

Any help would be appreciated,

Martin