Hi,
I have ported my datalogging program from Arduino Mega to the M5Stack Core 2 for AWS.
It all is now working as I expected except for one behavior.
On the Arduino, I could open an existing file on SD card and append data to the end of the file.
On the M5Stack, I can create, open, write to, and close a file on the SD card.
But when I re-open this file and write more data, it overwrites the existing data in the file.
It appears the FILE_WRITE specifier is allowing write access but is not moving the file pointer to its end...not sure why not?
Can anyone suggest what I am doing wrong or provide a workaround?
Thanks!

The relevant portion of my test code is below; apologies if it comes through with weird formatting:

if (!SD.begin(4,SPI,40000000)) { // ******M5 CS line is GPIO4
Serial.println("initialization failed!");
while (1);
}
Serial.println("initialization done.");

// open the file. note that only one file can be open at a time,
// so you have to close this one before opening another.

NewFile = SD.open("/TRIAL.TXT",FILE_WRITE);  
char message1[64]="This is just a test";  // 64 byte array
char message2[64]="It seems to be working so far!";

// delay(5000);
// if the file opened okay, write to it:
if (NewFile) {
NewFile.println(message1);
NewFile.println(message2);

// close the file:
NewFile.close();

} else {
// if the file didn't open, print an error:
Serial.println("error initially opening test.txt");
}

// Now try reopening file and writing more data into it

 delay(100);
 NewFile = SD.open("/TRIAL.TXT",FILE_WRITE);  //*******Reopen for more writing
 NewFile.println("Trying to add this additional line");
 NewFile.close();
 delay(100);

Felix,
OK, that works.
It prints to the LCD and I get output on the serial monitor.
Thanks for your assistance!
Regards,
Steve

Thanks for the good ideas!
In fact, I had initially loaded the M5Stack library, not the M5Core2 one.
I have since corrected this.
I do not see any activity in the serial monitor.

Below is the test program I uploaded.
I now am getting a compiler error:
'class M5Core2' has no member named 'Power'.
Any suggestions on what's wrong now?

#include <M5Core2.h>

/* After M5Core is started or reset
the program in the setUp () function will be run, and this part will only be run once.
After M5Core is started or reset, it will start to execute the program in the setup() function, and this part will only be executed once. /
void setup(){
M5.begin(); //Init M5Core. Initialize M5Core
M5.Power.begin(); //Init Power module. Initialize the power module
/ Power chip connected to gpio21, gpio22, I2C device
Set battery charging voltage and current
If used battery, please call this function in your project */
M5.Lcd.print("Hello World"); // Print text on the screen (string) Print text on the screen (string)
}

/* After the program in setup() runs, it runs the program in loop()
The loop() function is an infinite loop in which the program runs repeatedly
After the program in the setup() function is executed, the program in the loop() function will be executed
The loop() function is an endless loop, in which the program will continue to run repeatedly */
void loop() {

}

Hi, I am new to M5Stack use and I hope to port my existing Arduino code to the Core 2 AWS I just bought. It started up OK when first plugged into my PC and I was able to set the time. But after I compiled and uploaded the suggested test program (print "Hello World"), the screen froze and did not display this text. I powered unit off but now it is unresponsive and it won't do anything.

Any suggestions on what to try next?