ThingSpeak

Hello everyone, I am new to ThingSpeak and ESP32, I would like to send IMU sensor acceleration data from my ESP32 to ThingSpeak so that I can use this data for further analysis. I have tried the example code provided in this link: Bulk-Update and this works perfectly fine for me with the default update interval and post interval. I also attached the code here.

#include <Wire.h>
#include <Arduino.h>
#include <Adafruit_MCP4725.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_BNO055.h>
#include <utility/imumaths.h>
#include <WiFi.h>
#include "ThingSpeak.h"

// Define multiplexer address
#define TCAADDR 0x70

// Define imu and dac objects
Adafruit_BNO055 bno = Adafruit_BNO055(55, 0x28);

char jsonBuffer[500] = "[";

char ssid[] = "my ssid";
char pass[] = "my password";
WiFiClient client;

char server[] = "api.thingspeak.com";

unsigned long lastConnectionTime = 0;
unsigned long lastUpdateTime = 0;
const unsigned long postingInterval = 15L * 1000L;
const unsigned long updateInterval = 3L * 100L;

// To choose the multiplexer specific channel (between 0 and 7)
void tcaselect(uint8_t i){
  if (i > 7) return;

Wire.beginTransmission(TCAADDR);
Wire.write(1 << i);
Wire.endTransmission();
}

    void setup() {
      // put your setup code here, to run once:
  Wire.begin();
  Serial.begin(9600);
  while(!Serial);
  delay(1000);
  Serial.println("Serial communication set up");

// set up bno055
tcaselect(2);
if (!bno.begin()){
  Serial.println("Failed to connect to BNO055");
  while (1);
}

while(WiFi.status() != WL_CONNECTED){
  Serial.print("Attempting to connect to wifi");
  WiFi.begin(ssid, pass);
  delay(5000);
}
Serial.println("Connected to WiFi");
printWiFiStatus();
}

void loop() {
  // put your main code here, to run repeatedly.

if (millis() - lastUpdateTime >= updateInterval){
  updatesJson(jsonBuffer);
}
}

void updatesJson(char* jsonBuffer){
  /* JSON format for updates paramter in the API
   *  This examples uses the relative timestamp as it uses the "delta_t". You can 
also provide the absolute timestamp using the "created_at" parameter
 *  instead of "delta_t".
 *   "[{\"delta_t\":0,\"field1\":-70},{\"delta_t\":3,\"field1\":-66}]"
 */
// Format the jsonBuffer as noted above
strcat(jsonBuffer,"{\"delta_t\":");
unsigned long deltaT = (millis() - lastUpdateTime)/1000;
size_t lengthT = String(deltaT).length();
char temp[4];
String(deltaT).toCharArray(temp,lengthT+1);
strcat(jsonBuffer,temp);
strcat(jsonBuffer,",");

tcaselect(2);
sensors_event_t orientationData , angVelocityData , linearAccelData, magnetometerData, accelerometerData, gravityData;

bno.getEvent(&orientationData, Adafruit_BNO055::VECTOR_EULER);
bno.getEvent(&angVelocityData, Adafruit_BNO055::VECTOR_GYROSCOPE);
bno.getEvent(&linearAccelData, Adafruit_BNO055::VECTOR_LINEARACCEL);

float rssi = linearAccelData.acceleration.x; 
strcat(jsonBuffer, "\"field1\":");
lengthT = String(rssi).length();
String(rssi).toCharArray(temp,lengthT+1);
strcat(jsonBuffer,temp);
strcat(jsonBuffer,"},");
// If posting interval time has reached 15s, update the ThingSpeak channel with your 
data
if (millis() - lastConnectionTime >=  postingInterval) {
      size_t len = strlen(jsonBuffer);
      jsonBuffer[len-1] = ']';
      httpRequest(jsonBuffer);
}
lastUpdateTime = millis(); // Update the last update time
}

// Updates the ThingSpeakchannel with data
void httpRequest(char* jsonBuffer) {
/* JSON format for data buffer in the API
 *  This examples uses the relative timestamp as it uses the "delta_t". You can also 
provide the absolute timestamp using the "created_at" parameter
 *  instead of "delta_t".
 *   "{\"write_api_key\":\"YOUR-CHANNEL-WRITEAPIKEY\",\"updates\": 
[{\"delta_t\":0,\"field1\":-60},{\"delta_t\":15,\"field1\":200}, 
{\"delta_t\":15,\"field1\":-66}]
 */
// Format the data buffer as noted above
char data[500] = "{\"write_api_key\":\"59IISQVOXV5GGH0D\",\"updates\":"; // Replace 
YOUR-CHANNEL-WRITEAPIKEY with your ThingSpeak channel write API key
strcat(data,jsonBuffer);
strcat(data,"}");
// Close any connection before sending a new request
client.stop();
String data_length = String(strlen(data)+1); //Compute the data buffer length
Serial.println(data);
// POST data to ThingSpeak
if (client.connect(server, 80)) {
  client.println("POST /channels/1683708/bulk_update.json HTTP/1.1"); // Replace 
YOUR-CHANNEL-ID with your ThingSpeak channel ID
  client.println("Host: api.thingspeak.com");
  client.println("User-Agent: mw.doc.bulk-update (Arduino ESP8266)");
  client.println("Connection: close");
  client.println("Content-Type: application/json");
  client.println("Content-Length: "+data_length);
  client.println();
  client.println(data);
}
else {
  Serial.println("Failure: Failed to connect to ThingSpeak");
}
delay(250); //Wait to receive the response
client.parseFloat();
String resp = String(client.parseInt());
Serial.println("Response code:"+resp); // Print the response code. 202 indicates that 
the server has accepted the response
jsonBuffer[0] = '['; //Reinitialize the jsonBuffer for next batch of data
jsonBuffer[1] = '\0';
lastConnectionTime = millis(); //Update the last conenction time
}

void printWiFiStatus() {
  // Print the SSID of the network you're attached to:
  Serial.print("SSID: ");
  Serial.println(WiFi.SSID());

// Print your device IP address:
IPAddress ip = WiFi.localIP();
Serial.print("IP Address: ");
Serial.println(ip);

// Print the received signal strength:
long rssi = WiFi.RSSI();
Serial.print("signal strength (RSSI):");
Serial.print(rssi);
Serial.println(" dBm");
}

However, when I tried to change the update interval to 0.3s (30Hz), the following error massage was given in the Arduino monitor: Guru Meditation Error: Core 1 panic'ed (LoadProhibited). Exception was unhandled.

Could someone please help me with this issue. If anything else is needed, I will update immediately.

Many thanks