Dual Mega +WiFi Exception when using WiFi.begin(ssid, password);

Development Tools IDE 1.x
1

Hello,

I have read many posts and could not really find a solution to my problem. and quite a few posts are in different languages...
I have a few Dual Mega + Wifi "WeMOS Mega + WiFi R3 AT mega2560 + ESP8266 USB-TTL Arduino Mega NodeMCU...." So I have tried this on more than one hardware setup and the results are the same.

I can program both the Mega side and the ESP8266. But at a certain stage. The ESP8266 always comes up with an Exception error. The debug window get flooded with exception code.

I have narrowed it down to the "WiFi.begin(ssid, password);" as soon as I include this line the code screws up and I get exception codes.

Just simplifying my code to the bare minimum causes the problem:

#include <ESP8266WebServer.h>

const char* ssid = "";
const char* password = "****";

ESP8266WebServer server(80);

void setup(void){
Serial.begin(115200);

// start WiFi
WiFi.begin(ssid, password);
Serial.println("");
}

void loop(void){
delay(1000);
}

I have tried the ESP8266WebServer.h, WiFiEsp.h, ESP8266WiFi.h and various other libraries.
But when I run the code in the ESP8266 part of the dual card, the debug window is flooded with exceptions.

When I use the WiFiEsp.h library, I get the following, then exception 28
17:08:58.490 -> --------------- CUT HERE FOR EXCEPTION DECODER ---------------
17:08:58.490 ->
17:08:58.490 -> ets Jan 8 2013,rst cause:2, boot mode:(3,6)
17:08:58.490 ->
17:08:58.537 -> load 0x4010f000, len 3584, room 16
17:08:58.537 -> tail 0
17:08:58.537 -> chksum 0xb0
17:08:58.537 -> csum 0xb0
17:08:58.537 -> v2843a5ac
17:08:58.537 -> ~ld
17:08:58.583 ->
17:08:58.583 -> --------------- CUT HERE FOR EXCEPTION DECODER ---------------

17:08:58.583 -> --------------- CUT HERE FOR EXCEPTION DECODER ---------------
17:08:58.583 ->
17:08:58.583 -> Exception (28):
17:08:58.583 -> epc1=0x40201d2c epc2=0x00000000 epc3=0x00000000 excvaddr=0x00000000 depc=0x00000000

and if I use either the ESP8266WebServer.h or ESP8266WiFi.h libraries, I get the same start and then exception 3

17:24:57.770 -> --------------- CUT HERE FOR EXCEPTION DECODER ---------------
17:24:57.770 ->
17:24:57.770 -> ets Jan 8 2013,rst cause:2, boot mode:(3,6)
17:24:57.770 ->
17:24:57.817 -> load 0x4010f000, len 3584, room 16
17:24:57.817 -> tail 0
17:24:57.817 -> chksum 0xb0
17:24:57.817 -> csum 0xb0
17:24:57.817 -> v2843a5ac
17:24:57.817 -> ~ld
17:24:57.864 ->
17:24:57.864 -> --------------- CUT HERE FOR EXCEPTION DECODER ---------------

17:24:57.864 -> --------------- CUT HERE FOR EXCEPTION DECODER ---------------
17:24:57.864 ->
17:24:57.864 -> Exception (3):
17:24:57.864 -> epc1=0x40100718 epc2=0x00000000 epc3=0x00000000 excvaddr=0x4006e991 depc=0x00000000

The debug decoder tells me resp. as follows, but it makes no sense to me.

Can anybody tell me what I am doing wrong?

Exception 28: LoadProhibited: A load referenced a page mapped with an attribute that does not permit loads
PC: 0x40201d2c: EspDrv::espEmptyBuf(bool) at C:\Users\hvegt\Documents\Arduino\libraries\WiFiEsp\src\utility\EspDrv.cpp line 1094
EXCVADDR: 0x00000000

Decoding stack results
0x402046c1: uart_set_debug(int) at C:\Users\hvegt\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.7.4\cores\esp8266\uart.cpp line 933
0x402020c7: EspDrv::sendCmd(__FlashStringHelper const*, int) at C:\Users\hvegt\Documents\Arduino\libraries\WiFiEsp\src\utility\EspDrv.cpp line 998
0x4020216a: EspDrv::config(IPAddress) at C:\Users\hvegt\Documents\Arduino\libraries\WiFiEsp\src\utility\EspDrv.cpp line 230
0x40202620: HardwareSerial::begin(unsigned long, SerialConfig, SerialMode, unsigned char, bool) at C:\Users\hvegt\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.7.4\cores\esp8266\HardwareSerial.cpp line 51
0x40201401: WiFiEspClass::config(IPAddress) at C:\Users\hvegt\Documents\Arduino\libraries\WiFiEsp\src\WiFiEsp.cpp line 85
0x40201344: setup() at C:\Users\hvegt\Documents\Arduino\NewESP826602/NewESP826602.ino line 25
0x402033f0: loop_wrapper() at C:\Users\hvegt\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.7.4\cores\esp8266\core_esp8266_main.cpp line 194

and

Exception 3: LoadStoreError: Processor internal physical address or data error during load or store
PC: 0x40100718: umm_malloc_core(size_t) at C:\Users\hvegt\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.7.4\cores\esp8266\umm_malloc\umm_malloc.cpp line 433
EXCVADDR: 0x4006e991

Decoding stack results
0x40100900: malloc(size_t) at C:\Users\hvegt\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.7.4\cores\esp8266\umm_malloc\umm_malloc.cpp line 552
0x40100b50: calloc(size_t, size_t) at C:\Users\hvegt\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.7.4\cores\esp8266\umm_malloc\umm_malloc.cpp line 902
0x4010027c: pvPortZalloc(size_t, char const*, int) at C:\Users\hvegt\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.7.4\cores\esp8266\heap.cpp line 301
0x40100c2d: __wrap_spi_flash_read(uint32_t, uint32_t*, size_t) at C:\Users\hvegt\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.7.4\cores\esp8266\core_esp8266_phy.cpp line 309
0x40100647: umm_free_core(void*) at C:\Users\hvegt\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.7.4\cores\esp8266\umm_malloc\umm_malloc.cpp line 351
0x40100c2d: __wrap_spi_flash_read(uint32_t, uint32_t*, size_t) at C:\Users\hvegt\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.7.4\cores\esp8266\core_esp8266_phy.cpp line 309
0x40201962: ESP8266WiFiSTAClass::begin(char const*, char const*, int, unsigned char const*, bool) at C:\Users\hvegt\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.7.4\libraries\ESP8266WiFi\src\ESP8266WiFiSTA.cpp line 189
0x402018b7: ESP8266WiFiSTAClass::begin(char const*, char const*, int, unsigned char const*, bool) at C:\Users\hvegt\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.7.4\libraries\ESP8266WiFi\src\ESP8266WiFiSTA.cpp line 157
0x40100900: malloc(size_t) at C:\Users\hvegt\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.7.4\cores\esp8266\umm_malloc\umm_malloc.cpp line 552
0x4020491b: base_from_object at /workdir/repo/gcc/libgcc/unwind-dw2-fde.c line 254
0x40204add: read_encoded_value_with_base at /workdir/repo/gcc/libgcc/unwind-pe.h line 257
0x40100900: malloc(size_t) at C:\Users\hvegt\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.7.4\cores\esp8266\umm_malloc\umm_malloc.cpp line 552
0x40203631: uart_flush(uart_t*) at C:\Users\hvegt\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.7.4\cores\esp8266\uart.cpp line 544
0x40203943: uart_init(int, int, int, int, int, size_t, bool) at C:\Users\hvegt\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.7.4\cores\esp8266\uart.cpp line 668
0x40203b05: uart_set_debug(int) at C:\Users\hvegt\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\2.7.4\cores\esp8266\uart.cpp line 933
0x4020105c: setup() at

2

you run the WiFiEsp library on en esp8266? that is for other Arduino to use the AT firmware on esp8266.

try first the WiFiScan example of the ESP8266WiFi library

3

Thank you Juraj, I was going to get back to this, but I was concentrating on the other post. I understand now what you are suggesting. I like the option using the WiFiEspAT and doing all the code in the Mega and just sending AT commands to the ESP8266, because that way I don't have to change all the DIP switches every time I make a change or need to fault-find. Possible drawback would be speed I suppose. But so far I have enough capacity to do what I want to do.
(I have had a datalogger for temperature and power consumption reading sensors, webclients and storing to SD or USB using a raspberryPI for a number of years, but that does not handle power interruptions too good. Hence I have re-written for the Arduino Mega).

I think we can close this post.