I am trying to use the ADC module from an assembly program running in the
PRU, but I've got an infinite loop as pointed in the code below. I would
like to know if I forgot to enable interrupts somehow, and how would it be
possible to sample signals using the PRU. (My platform is a BeagleBone
Black).
Thanks in advance.
CODE:
// testADCPRU2.p
*.*origin 0
*.*entrypoint CONFIGURE
#define ADC_TSC_REGISTERS_BASE 0x44E0D000
#define STEPCONFIG1_OFFSET 0x64
#define STEPDELAY1_OFFSET 0x68
#define STEPENABLE_OFFSET 0x54
#define IRQENABLE_SET_OFFSET 0x2C
#define IRQSTATUS_OFFSET 0x28
#define CTRL_OFFSET 0x40
#define FIFO0THRESHOLD_OFFSET 0xE8
#define FIFO0DATA_OFFSET 0x100
#define CONST_PRUCFG C4
#include "testADCPRU2.hp"
CONFIGURE*:*
// Clear syscfg[standby_init] to enable ocp master port
// spruhf8 AM335x PRU-ICSS Reference Guide 11.1.2
LBCO r0*,* CONST_PRUCFG*,* 4*,* 4
CLR r0*,* r0*,* 4
SBCO r0*,* CONST_PRUCFG*,* 4*,* 4
//R1 --> STEPCONFIG1
MOV32 R1*,* ADC_TSC_REGISTERS_BASE *+*
STEPCONFIG1_OFFSET
MOV32 R2*,* 0x00000000
//STEPCONFIG1 = 0x00000000
SBBO R2*,* R1*,* 0*,* 4
//R1 --> STEPDELAY1
MOV R1*,* ADC_TSC_REGISTERS_BASE *+*
STEPDELAY1_OFFSET
MOV R2*,* 0x00005DC0
//STEPDELAY1 = 0x00005DC0 (open delay of 24000 cycles =
1 ms)
SBBO R2*,* R1*,* 0*,* 4
//R1 --> STEPENABLE
MOV R1*,* ADC_TSC_REGISTERS_BASE *+*
STEPENABLE_OFFSET
MOV R2*,* 0x00000002
//STEPENABLE = 0x00000002 (enable step 1)
SBBO R2*,* R1*,* 0*,* 4
//enable fifo0_threshold interrupt
//R1 --> IRQENABLE_SET
MOV R1*,* ADC_TSC_REGISTERS_BASE *+*
IRQENABLE_SET_OFFSET
MOV R2*,* 0x00000004
SBBO R2*,* R1*,* 0*,* 4
//1 sample limit
//R1 --> FIFO0THRESHOLD
MOV R1*,* ADC_TSC_REGISTERS_BASE *+*
FIFO0THRESHOLD_OFFSET
MOV R2*,* 0x00000000
SBBO R2*,* R1*,* 0*,* 4
TESTPRU*:*
//R3: POINTER TO REGISTER IRQSTATUS
MOV R3*,* ADC_TSC_REGISTERS_BASE *+*
IRQSTATUS_OFFSET
//R4: POINTER TO REGISTER FIFO0DATA
MOV R4*,* ADC_TSC_REGISTERS_BASE *+*
FIFO0DATA_OFFSET
//enable step_ID_tag, enable TSC_ADC_SS module
//R1 --> CTRL
MOV R1*,* ADC_TSC_REGISTERS_BASE *+* CTRL_OFFSET
MOV R2*,* 0x00000003
SBBO R2*,* R1*,* 0*,* 4
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// The execution gets stuck in this "RETURN" loop, while polling the
FIFO0THRESHOLD
// event. It seems like an infinite loop, an event that never happens
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
RETURN*:* //Load R1 with the contents of IRQSTATUS (R3 -->
IRQSTATUS)
LBBO R1*,* R3*,* 0*,* 4
//Check bit 2 = FIFO0THRESHOLD event
QBBC RETURN*,* R1*.*t2
//Load R1 with the sampled value (R4 --> FIFO0DATA)
LBBO R1*,* R4*,* 0*,* 4
// Configure the block index register for PRU0 by
setting c24_blk_index[7:0] and
// c25_blk_index[7:0] field to 0x00 and 0x00,
respectively. This will make C24 point
// to 0x00000000 (PRU0 DRAM) and C25 point to 0x00002000
(PRU1 DRAM).
MOV R2*,* 0x00000000
MOV R3*,* CTBIR_0
ST32 R2*,* R3
//Store sampled value
SBCO R1*,* CONST_PRU_DRAM*,* 0*,* 4
MOV R31*.*b0*,* PRU0_ARM_INTERRUPT *+* 16
HALT
--
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