Guru Meditation Error: Core 1 panic'ed (Cache disabled but cached memory region accessed) ESP32 ARDUINO IDE

[igrr]

From @jt040-jetnet on November 21, 2017 10:21

i am using esp32 in arduino core
i am using touch key feature in interrupt
getting below error and my esp32 gets restart ,
please suggest how to fix it,
Guru Meditation Error: Core 1 panic'ed (Cache disabled but cached memory region accessed)
Register dump:
PC : 0x400d13f4 PS : 0x00060034 A0 : 0x40082388 A1 : 0x3ffc0bf0
A2 : 0x00000000 A3 : 0x3ffc3590 A4 : 0x00000001 A5 : 0x40086408
A6 : 0x00000003 A7 : 0x00060e23 A8 : 0x80081142 A9 : 0x04000c01
A10 : 0x00060e23 A11 : 0x00000000 A12 : 0x00060023 A13 : 0x3ffc0bd0
A14 : 0x3ffc0c18 A15 : 0x00000001 SAR : 0x0000001e EXCCAUSE: 0x00000007
EXCVADDR: 0x00000000 LBEG : 0x400014fd LEND : 0x4000150d LCOUNT : 0xffffffff

Backtrace: 0x400d13f4:0x3ffc0bf0 0x40082385:0x3ffc0c10 0x4008f54f:0x00000000

Rebooting...
ets Jun 8 2016 00:22:57

rst:0x3 (SW_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
configsip: 0, SPIWP:0xee
clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
mode:DIO, clock div:1
load:0x3fff0010,len:4
load:0x3fff0014,len:716
load:0x40078000,len:0
load:0x40078000,len:11572
entry 0x40078a14

Copied from original issue: espressif/esp-idf#1299

[igrr]

Fwiw, this looks like it is caused by interrupt firing while cache is disabled, see #489.

[stickbreaker]

the code that was triggered by the interrupt did not have the IRAM_ATTR attribute.

Most O/S library function cannot be called from an ISR. Review your code, make sure that every function it calls is local. and has the IRAM_ATTR attribute. For example, you Cannot call Serial.print() from an ISR.

Chuck.

[jt040-jetnet]

sorry to say but i didnt get how to fix the issue as i am using arduino ide

[stickbreaker]

Read through this info for a more detailed discussion:

General Notes

The function you attach to the interrupt:

static volatile uint16_t intTriggerCount=0; // this variable will be changed in the ISR, and Read in main loop
// static: says this variable is only visible to function in this file, its value will persist, it is a global variable
// volatile: tells the compiler that this variables value must not be stored in a CPU register, it must exist
//   in memory at all times.  This means that every time the value of intTriggeredCount must be read or
//   changed, it has be read from memory, updated, stored back into RAM, that way, when the ISR 
//   is triggered, the current value is in RAM.  Otherwise, the compiler will find ways to increase efficiency
//   of access.  One of these methods is to store it in a CPU register, but if it does that,(keeps the current
//   value in a register, when the interrupt triggers, the Interrupt access the 'old' value stored in RAM, 
//   changes it, then returns to whatever part of the program it interrupted.  Because the foreground task,
//   (the one that was interrupted) has no idea the RAM value has changed, it uses the value it 'know' is 
//   correct (the one in the register).  

void IRAM_ATTR isr(){  //IRAM_ATTR tells the complier, that this code Must always be in the 
// ESP32's IRAM, the limited 128k IRAM.  use it sparingly.
intTriggeredCount++;
}

void setup(){
Serial.begin(115200);
pinMode(5,INPUT_PULLUP);
attachInterrupt(digitalPinToInterrupt(5),isr,FALLING);
}

void loop(){
// magic happens her
static uint16_t old_Value=0; // this variable is only visible inside loop(),
// but it is persistent, It is only init'ed
// once, and each time through loop() it remembers its prior value

if(old_Value != intTriggeredCount){
  old_Value = intTriggeredCount; // something to compare against
  Serial.printf(" Someone grounded pin 5 again, it is the %d's time! Better call the Cops!",intTriggeredCount);
}

Chuck.

[jt040-jetnet]

thanks stickbreaker
IRAM_ATTR works for my application

[tcsaba101]

Thanks stickbreaker!
Also working in our case!

[copercini]

Closed due it was solved =)

[echoGee]

@stickbreaker @igrr : I logged an issue #1352 . Could you kindly look at it to see if its similar to #855 ? The IRAM_ATTR solution mentioned here didn't work though.

[felixqueisler]

Beware, not only the ISR (Interrupt) has to be in IRAM!
Every function called from the ISR also needs to be declared as IRAM_ATTR yourFunction() {}.

I made the mistake of using a normal function in my ISR and my ESP32 kept panicing when my code wanted to use the Preferences library (saving data to flash memory). I fixed it by also writing IRAM_ATTR before those function names.

Edit: It still happened and I found that you can't use analogRead() in the ISR either. I fixed it by setting a flag for it in the ISR. Now my code reads the pin in the superloop. A disadvantage is, that the value lags behind by 1 ISR.