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
