Unable to read from SD inside of tasks about arduino_freertos_library HOT 4 CLOSED

It looks like we got it working by opening the file in the setup and leaving it open in the task. IE, the file should already be opened by the time the task gets a hold of it.

from arduino_freertos_library.

I can confirm,

If I run the following piece of code I can write to the SD Card. If I run it in a task, it will create the text file, however it will not write anything to it.

File myBaro = SD.open("test.txt", FILE_WRITE);
baro.readBaro();
Serial.println(baro.getPressure());
myBaro.println("This should be working.");
myBaro.println(baro.getPressure());
delay(200);
myBaro.close();

Again, in setup it works 100%, but in a task for whatever reason it will not write to the SD Card.

from arduino_freertos_library.

I've had a quick look at this, and the Serial() class is used for writing text to the SD card.
There is a known issue with the Serial() class library. See issue #3. This same issue is probably occurring.

  Serial.print("Sensor Value: "); \\  Correctly prints the text "Sensor Value: "
  Serial.println(sensorValue);  \\  just a blank, but newline & CR are printed.

I'm still trying to figure out what is the underlying cause of entanglement. My suspicion is that it is to do with namespace and variable declaration.

from arduino_freertos_library.

That's good to hear.

I'm certain there is a String() class issue underlying this issue though.

The only avenue I have to investigate is the potential for a variable declaration / freeing issue in the difference between the Arduino implementation, where setup() and loop() are both called by the main() function and hence may have corresponding variable space, and the FreeRTOS case where main() is never called directly. But, I haven't nailed down anything concrete yet.

I've done a bit of investigation, and it seems necessary to declare Strings as Global variables, otherwise they get allocated each time the Task for() loop is run, and then reserve() space for them, to prevent reallocation. Also, conversion of int to String seems somehow problematic.

Some working code is here, on Issue #3, for reference.

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