Great Job! Do you also have a simple test file of test.ino, which is used to test the vendor interface. And if yes, could you please to share it. Thank you.
To make it simple, I just change the logData() function as follow
void logData()
{
// make a string for assembling the data to log:
String dataString = "";
// if the file is available, write to it:
if (dataFile) {...