ecap to read encoders on a 28xx

I had the same question but have not no clue for now. Now sure if this is correct and also some application (examples)

Yes, The ecap can be used as an encoder module. But the fundamental difference between the two is QEP gives the counts and ecap gives the timestamp. So if you wanted to use CAP as QEP then you need to implement a software counter. Give 1 encoder input (say A) to a capture pin and other(say B) to a GPIO. Whenever a capture interrupt comes increment/decrement the counter depending on the state of the GPIO. 

Actually this is exactly what a QEP module does. We implemented this using a capture module and GPIO but in MSP430. I'm not sure whether there are any sample codes but you can always check the control suite.

Vivek

Thanks Vivek. this solution seem to be reasonable.

One thing about set up the ecap, I am trying to capture on both side (rising & falling edges) on channel A but I can only capture on rising edge.

Here's my init for ecap:

#define

ECCTL1_INIT_STATE ( CAP1POL_RISING_EDGE + \

CAP2POL_FALLING_EDGE + \

CAPLDEN_ENABLE + \

CTRRST1_DIFFERENCE_TS + \

CTRRST2_DIFFERENCE_TS + \

EVTFLTPS_X_1 + \

EMULATION_FREE )

#define

ECCTL2_INIT_STATE ( CONTINUOUS_MODE + \

TSCNTSTP_FREE + \

SYNCI_DISABLE + \

SYNCO_DISABLE + \

CAPTURE_MODE )

void

F280X_CAP3_Init(QEP*p)

{

ECap3Regs.ECEINT.all = 0x0000; // Disable all capture interrupts

ECap3Regs.ECCLR.all = 0xFFFF; // Clear all CAP interrupt flags

// Init ECAP Control Registers 1 and 2 for ECAP3

ECap3Regs.ECCTL1.all = ECCTL1_INIT_STATE;

ECap3Regs.ECCTL2.all = ECCTL2_INIT_STATE;

ECap3Regs.ECCTL2.bit.TSCTRSTOP = 1; // Start Counter

ECap3Regs.ECCTL2.bit.REARM = 1; // arm one-shot

ECap3Regs.ECEINT.bit.CEVT1 = 1; // 1 events = interrupt

ECap3Regs.ECEINT.bit.CEVT2 = 1; // 1 events = interrupt

}

Do you have any idea ?