Hello,
I'm practicing with 28027 with its eCap function, using "Example_2802xECap_Capture_Pwm" sample project (along with TI's 2802x header files and examples package). In this example, it use ePWM3 to generate a PWM output on GPIO4, and measures GPIO4's output pulse via eCap1 on GPIO19, and the captured values in CAP1~CAP4 is very accurate -- exactly the same as what the PWM's settings. However, when I attempted to make use of eCap1 to captuer an external 32k signal (CMOS output, squre wave), the captured values in CAP1~CAP4 varies a lot around 1831, not exactly a fixed count! What may be the reason? I have tried over 2 more days, but without any progress, hope you can shed me some light on this.
Thank you very much.
Li dongsheng.
Below is the code for init.
void InitECapture()
{
ECap1Regs.ECEINT.all = 0x0000; // Disable all capture interrupts
ECap1Regs.ECCLR.all = 0xFFFF; // Clear all CAP interrupt flags
ECap1Regs.ECCTL1.bit.CAPLDEN = 0; // Disable CAP1-CAP4 register loads
ECap1Regs.ECCTL2.bit.TSCTRSTOP = 0; // Make sure the counter is stopped
// Configure peripheral registers
ECap1Regs.ECCTL2.bit.CONT_ONESHT = 1; // One-shot
ECap1Regs.ECCTL2.bit.STOP_WRAP = 3; // Stop at 4 events
ECap1Regs.ECCTL1.bit.CAP1POL = 0; // Rising edge
ECap1Regs.ECCTL1.bit.CAP2POL = 0; // Rising edge
ECap1Regs.ECCTL1.bit.CAP3POL = 0; // Rising edge
ECap1Regs.ECCTL1.bit.CAP4POL = 0; // Rising edge
ECap1Regs.ECCTL1.bit.CTRRST1 = 1; // Difference operation
ECap1Regs.ECCTL1.bit.CTRRST2 = 1; // Difference operation
ECap1Regs.ECCTL1.bit.CTRRST3 = 1; // Difference operation
ECap1Regs.ECCTL1.bit.CTRRST4 = 1; // Difference operation
ECap1Regs.ECCTL2.bit.SYNCI_EN = 0; // Disable sync in
ECap1Regs.ECCTL2.bit.SYNCO_SEL = 0; // Pass through
ECap1Regs.ECCTL1.bit.CAPLDEN = 1; // Enable capture units
ECap1Regs.ECCTL2.bit.TSCTRSTOP = 1; // Start Counter
ECap1Regs.ECCTL2.bit.REARM = 1; // arm one-shot
ECap1Regs.ECCTL1.bit.CAPLDEN = 1; // Enable CAP1-CAP4 register loads
ECap1Regs.ECEINT.bit.CEVT4 = 1; // 4 events = interrupt
}
void InitECap1Gpio(void)
{
EALLOW;
/* Enable internal pull-up for the selected pins */
// Pull-ups can be enabled or disabled by the user.
// This will enable the pullups for the specified pins.
// Comment out other unwanted lines.
// GpioCtrlRegs.GPAPUD.bit.GPIO5 = 0; // Enable pull-up on GPIO5 (CAP1)
GpioCtrlRegs.GPAPUD.bit.GPIO19 = 0; // Enable pull-up on GPIO19 (CAP1)
// Inputs are synchronized to SYSCLKOUT by default.
// Comment out other unwanted lines.
// GpioCtrlRegs.GPAQSEL1.bit.GPIO5 = 0; // Synch to SYSCLKOUT GPIO5 (CAP1)
GpioCtrlRegs.GPAQSEL2.bit.GPIO19 = 0; // Synch to SYSCLKOUT GPIO19 (CAP1)
/* Configure eCAP-1 pins using GPIO regs*/
// This specifies which of the possible GPIO pins will be eCAP1 functional pins.
// Comment out other unwanted lines.
// GpioCtrlRegs.GPAMUX1.bit.GPIO5 = 3; // Configure GPIO5 as CAP1
GpioCtrlRegs.GPAMUX2.bit.GPIO19 = 3; // Configure GPIO19 as CAP1
EDIS;
}