BBB, PRUSSV2, using timer on IEP

Hi

I'm trying to use IEP timer on PRU on my BeagleBone Black, but without much luck. I would like to use it for precise timing, so I have created demo app that should demonstrate IEP timer capabilities. Demo app should work in following way:

• first turns LED on one of GPIO pins
• then starts timer
• pools timer value until reaches some predefined value
• turns LED off
• exits

Part with runing LEDs on/off works fine, problem is with timer. From what I have tried so far, I'm not able to get it running. Here are the steps that I performed in the code to start counter:

1. set counter value to 0
2. enable timer clock PRU_ICSS_CFG.CGR.IEP_CLK_EN=1 (although this should be already on upon reset)
3. // start counter IEP_GLOBAL_CFG.CNT_ENABLE = 1
   

Code gets stuck when pooling counter value (red bellow) - it  never reaches desired value. Did I missed something in initialization? any hint?

Here is code of sample app:

.origin 0
.entrypoint START

#define PRU0_ARM_INTERRUPT       19
#define AM33XX

#define GPIO0                    0x44E07000    // base address of GPIO 0

#define GPIO_OE                  0x134        // offset of the register that defines pin directions
#define GPIO_CLEARDATAOUT        0x190        // offset of the register used for setting pin to LOW
#define GPIO_SETDATAOUT          0x194        // offset of the register used for setting pin to HIGH
#define IEP                      0x2E000        // base address of Industrial Etherne Peripheral (IEP)

#define PIN_GPIO_0_26            1<<26        // references GPIO 0 pin 26 (P8-14 on BBB headers)

#define IEP_GLOBAL_CFG           0
#define IEP_COUNT                0xc

#define rGPIO0Base               r0
#define rOE                      r1
#define rSetDataOut              r2
#define rClearDataOut            r3
#define rOutPin                  r4
#define rIEPBase                 r5


#define rT1                      r16
#define rT2                      r17

START:
                                             
    LBCO    rT1, c4, 4, 4                     // Load Byte Constant Offset
    CLR     rT1, rT1, 4                       // clears r0 and copies to destination r0
    SBCO    rT1, c4, 4, 4                     // Store byte constant table offset

    MOV     rGPIO0Base, GPIO0                 // setup needed address offsets
    MOV     rOE, GPIO_OE
    MOV     rSetDataOut, GPIO_SETDATAOUT
    MOV     rClearDataOut, GPIO_CLEARDATAOUT
    MOV     rOutPin, PIN_GPIO_0_26
    MOV     rIEPBase, IEP

    MOV     rT1, 0x00000000                    // set all pins on GPIO 0 as output
    SBBO    rT1, rGPIO0Base, rOE, 4
        
    // turn led on
    SBBO    rOutPin, rGPIO0Base, rSetDataOut, 4        

    // init counter value to 0
    MOV     rT1, 0
    SBBO    rT1, rIEPBase, IEP_COUNT, 4
        
    // enable timer clock PRU_ICSS_CFG.CGR.IEP_CLK_EN=1
    LBCO    rT1, C4, 0x10, 4                    
    SET     rT1, 17                                
    SBCO    rT1, C4, 0x10, 4                    

    // start counter IEP_GLOBAL_CFG.CNT_ENABLE = 1        
    LBBO    rT1, rIEPBase, IEP_GLOBAL_CFG, 4    
    SET     rT1, 0
    SBBO    rT1, rIEPBase, IEP_GLOBAL_CFG, 4
    
    // wait until counter reaches desired value
    MOV     rT1, 1                                // for testing only -> counter never reaches this value
L1:
    LBBO    rT2, rIEPBase, IEP_COUNT, 4
    QBLT    L1, rT1, rT2
    

    // led off
    SBBO    rOutPin, rGPIO0Base, rClearDataOut, 4    

    MOV     r31.b0, PRU0_ARM_INTERRUPT+16    //tell the c program we are done (just remove it if your c program does not handle the interrupt)

HALT

BR

Ivan