Teensy: Crash when returning a array

[Joe7M]

Hi Chris,

I added I2C support to SmallBACIS on Teensy. It works so far quite nice. I use the interactive mode. But I have a problem, that my Teensy 4.1 crashes after some time, when I return the bytes received from a I2C device as an array. Here the source code:

static int cmd_i2c_read(var_s *self, int argc, slib_par_t *args, var_s *retval) {
  uint8_t  address = get_param_int(argc, args, 0,  0);
  uint32_t bytes   = get_param_int(argc, args, 1,  1);
  uint8_t  stop    = get_param_int(argc, args, 2,  1);

  if (address == 0) {
    v_setstr(retval, ERR_PARAM);
    return 0;
  }

  //uint8_t *buffer = new uint8_t[bytes];
  //int interfaceNumber = self->v.m.id;
  //TwoWire *ptrWire;
  //ptrWire = getI2C(interfaceNumber);

  //ptrWire->requestFrom(address, bytes, stop);
  //int len = ptrWire->readBytes(buffer, bytes);

  if(bytes > 1) {
    v_toarray1(retval, bytes);
    for(uint32_t ii = 0; ii < bytes; ii++) {
      //v_setint(v_elem(retval, ii), buffer[ii]);
      v_setint(v_elem(retval, ii), 1);
    }
  }
  else {
    //v_setint(retval, buffer[0]);
    v_setint(retval, 1);
  }

  //delete[] buffer;
  return 1;
}

static int cmd_openi2c(int argc, slib_par_t *args, var_t *retval) {
  uint8_t  interfaceNumber = get_param_int(argc, args, 0,  0);
  if (interfaceNumber > 2) {
    v_setstr(retval, ERR_PARAM);
    return 0;
  }

  map_init(retval);
  v_create_callback(retval, "write", cmd_i2c_write);
  v_create_callback(retval, "read", cmd_i2c_read);
  v_create_callback(retval, "setClock", cmd_i2c_setClock);
  retval->v.m.id = interfaceNumber;

  getI2C(interfaceNumber)->begin();

  return 1;
}

static FuncSpec lib_func[] = {
  {0, 0, "GETTEMP", cmd_get_temperature},
  {0, 0, "GETCPUSPEED", cmd_get_cpu_speed},
  {1, 1, "OPENANALOGINPUT", cmd_openanaloginput},
  {1, 1, "OPENDIGITALINPUT", cmd_opendigitalinput},
  {1, 1, "OPENDIGITALOUTPUT", cmd_opendigitaloutput},
  {0, 1, "OPENSERIAL", cmd_openserial},
  {0, 1, "OPENI2C", cmd_openi2c}
};

when calling cmd_i2c_read several thousand times (i.e reading constantly the room temperature with an BMP180), and receiving 2 bytes ( that means, that the ìf(bytes > 1) section is executed, the Teensy crashes. The SmallBASIC program looks like this:

import teensy

const ADDRESS = 0x77

I2C = teensy.OpenI2C(1)    ' Using pins 16 and 17
I2C.setClock(100000)

while(1)
  ii++
  print ii
  a = I2C.read(ADDRESS, 2)
  delay(500)
wend

Here the crash report:

CrashReport:
  A problem occurred at (system time) 0:1:37
  Code was executing from address 0x16FAC
  CFSR: 82
        (DACCVIOL) Data Access Violation
        (MMARVALID) Accessed Address: 0x41
  Temperature inside the chip was 31.85 °C
  Startup CPU clock speed is 600MHz
  Reboot was caused by auto reboot after fault or bad interrupt detected

Do you have an idea why? Am I doing something wrong with returning an array?

Best regards, Joerg

[chrisws]

Perhaps some kind of memory corruption, or maybe some memory not being de-allocated?
I'll order a BMP180 and take a look. It's pretty wild how inexpensive these little gadgets are.

[Joe7M]

No need to order. I think it is a problem of v_setint(v_elem(retval, ii), 1);. In the code above cmd_i2c_read doesn't call any I2C code and there is also no memory allocation. I commented it and it still crashes.

[Joe7M]

I pushed my I2C changes to my SmallBASIC repository: https://github.com/Joe7M/SmallBASIC/tree/master. In the teensy sample folder you can find two I2C sensors. Both working fine, until the crash happens.
Just as an info. I got also PWM running. Next is OneWire to talk to the very popular Dallas DS18B20 temperature sensor.