ESP32S3 FSM ULP Code Question

[dmydmy]

Hi all,
I have a question regarding my ESP32S3 FSM ULP program. This one here works, when I periodically read out address 130 in the Arduino code I can see the counter increasing

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const ulp_insn_t ulp_prog[] = {
    M_LABEL(0),
    I_MOVI(R1, 130),
    I_LD(R0, R1, 0),
    I_ADDI(R0, R0, 1),
    I_ST(R0, R1, 0),
    M_BX(0)
};

However, if want to run the counter up to 100 and then enter an infinite loop the counter stops at 1. why?

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const ulp_insn_t ulp_prog[] = {
    M_LABEL(0),
    I_MOVI(R1, 130),
    I_LD(R0, R1, 0),
    I_ADDI(R0, R0, 1),
    I_ST(R0, R1, 0),
    I_BL(3, 100),
    M_LABEL(3),
    M_BX(3),
    M_BX(0)
};

Why doesn't it branch to M_BX(0) when R0 is less than 100, increment the counter by, repeat until R0 = 100 and then do an infinite loop M_LABEL(3), M_BX(3)?

For reference, here's the entire Arduino code:

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#include "esp32s3/ulp.h"
#include "ulp_common.h"

// Define the ULP program
const ulp_insn_t ulp_prog[] = {
    M_LABEL(0),
    I_MOVI(R1, 130),
    I_LD(R0, R1, 0),
    I_ADDI(R0, R0, 1),
    I_ST(R0, R1, 0),
    I_BL(3, 100),
    M_LABEL(3),
    M_BX(3),
    M_BX(0)
};

void setup() {
  Serial.begin(115200);
  
  // Initialize ULP
  size_t prog_size = sizeof(ulp_prog) / sizeof(ulp_insn_t);
  ESP_ERROR_CHECK(ulp_process_macros_and_load(0, ulp_prog, &prog_size));
  
  // Start ULP program
  ESP_ERROR_CHECK(ulp_run(0));

  // Initialize counter to 0
  RTC_SLOW_MEM[130] =  0;
}

void loop() {
  // Read counter value
  uint32_t counter = RTC_SLOW_MEM[130];
  Serial.printf("Counter value: %ld\n", counter);
  
  delay(1000);  // Wait for 1 second before next read
}

Thanks a lot in advance!
dmy

[dmydmy]

Found the solution.

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M_LABEL(),

does NOT count as an instruction. So it needs to be

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I_BL(2, 100),

for the code to work.