I’m using a Boron and the Adalogger FeatherWing with this library to publish some sensor data to the cloud or record the data to the SD card if the Boron cannot connect to the cell network. That part is working just fine.
The tricky part comes when I want to read the data from the file after the Boron has reconnected and publish that data to the cloud, marking it in the file as confirmed so that lines from the file will not be published more than once.
Here is my basic setup:
File with example sensor data (relevant character for identifying lines is marked with ‘^’)
p08/21/2019 19:44:51,03.1,01.2,105.4,41.5,0983.0
p08/21/2019 19:44:52,03.1,01.2,105.4,41.5,0983.0
p08/21/2019 19:44:53,03.1,01.2,105.4,41.5,0983.0
p08/21/2019 19:44:54,03.1,01.2,105.4,41.5,0983.0
p08/21/2019 19:45:55,03.1,01.2,105.4,41.5,0983.0
^
When data is written to the card, it is marked ‘p’ (for pending). My program works up to this point just fine
I then use this method, readLine, that I have added to the SdCardLogHandlerRK.cpp file to scan the file for the character ‘p’. If a ‘p’ is found, it will scan the next 48 characters (There are 47 characters in a line excluding the first ‘p’ label and I left one character for null termination). The 48th character encountered by the fgets method would be a line break anyway, which the method is set to stop at by default as a delimiter. After the data is read into the char* textLine, the program backtracks the cursor back to the ‘p’ label and writes over it with a ‘c’ (for confirmed).
String SdCardPrintHandler::readLine (char textLine[]) {
FatFile tempFile;
char currentChar; //will track what character the cursor is viewing
//initialized array with known values so that I would know if it was modified
for (int i = 0; i < 48; i++) {
textLine[i] = char('o');
}
// return string for the same data being written to the array
String ab = "";
// opens the working directory
if (logsDir.open(sd.vwd(), logsDirName, O_READ)) {
FatFile tempFile;
tempFile.openNext(&logsDir, O_RDWR | O_SYNC); //opens the most recently made file in the directory for reading and writing
tempFile.rewind(); // sets cursor to beginning of file if not already
int currentByte = tempFile.read(¤tChar, 1); // reads the first char in the file
while (currentChar != 'p' && currentByte > 0) { // continues reading the next character until 'p' or EOF is found
currentByte = tempFile.read(¤tChar, 1);
}
// if 'p' was found before EOF, read 48 bytes out of the file after 'p'
if (currentChar == 'p') {
tempFile.fgets(textLine, 48);
tempFile.seekCur(-48);
tempFile.write('c'); // marks data as confirmed published
}
}
tempFile.close(); // close the file as I am done with it
ab = ab + textLine; // append the empty string with the information in the char array
return ab; // return string should have the same data as the char array
}
The method is called from the main program file in loop()
RTCLogger rtclogger;
int readTime;
void setup () {
rtclogger.initialize();
readTime = millis();
}
void loop() {
if (millis() - readTime >= 10000) { // code runs every 10 seconds(ish)
char arr[48]; // array to write data from file to
// String to write array to, also calls method in RTCLogger class
String stri = rtclogger.readLineFromPending(arr);
// publish the array and string up to the cloud (I had both in case one was working and the other wasn't)
Particle.publish("line(chars): ", arr, PRIVATE);
Particle.publish("line(string): ", stri, PRIVATE);
// resets timer to the current time the device has been on
readTime = millis();
}
}
This is the method from RTCLogger that will call my readLine() method
SdCardPrintHandler printToPending(sd, SD_CHIP_SELECT, SPI_FULL_SPEED);
void RTCLogger::initialize () {
pinMode(SD_CHIP_SELECT, OUTPUT); // Sets cs pin as an output
printToPending.withLogsDirName("pending"); // changes working directory name to "pending"
}
String RTCLogger::readLineFromPending (char buf[]) {
// s will contain data from file, also calls to the readLine method
// passed buf array will also be populated with data from the file
String s = printToPending.readLine(buf);
return s; // return s after checking file for unpublished data
}
My program when given the example file I included earlier will successfully see the first character as ‘p’, replacing the ‘p’ with ‘c’, and publishing the line to the cloud.
The problem lies in that any further attempts to run this method in the same power cycle will return an array and String filled with ‘o’, indicating that it did not find ‘p’ in the file.
Here are the results:
- File
c08/21/2019 19:44:51,03.1,01.2,105.4,41.5,0983.0
p08/21/2019 19:44:52,03.1,01.2,105.4,41.5,0983.0
p08/21/2019 19:44:53,03.1,01.2,105.4,41.5,0983.0
p08/21/2019 19:44:54,03.1,01.2,105.4,41.5,0983.0
p08/21/2019 19:45:55,03.1,01.2,105.4,41.5,0983.0
- Publishes to console
line(string): oooooooooooooooooooooooooooooooooooooooooooooooo
line(chars): oooooooooooooooooooooooooooooooooooooooooooooooo
line(string): 08/21/2019 19:44:51,03.1,01.2,105.4,41.5,0983.0
line(chars): 08/21/2019 19:44:51,03.1,01.2,105.4,41.5,0983.0
The program will continue to do this, until I restart the boron. If I don’t change the file before the program runs again, the program will then skip the first line, as it is supposed to, now that the line starts with ‘c’ and not ‘p’. It will then continue on down to the second line, where it will see ‘p’, and successfully handle the second line, but will fail on reading any further lines.
- File after restarting the boron
c08/21/2019 19:44:51,03.1,01.2,105.4,41.5,0983.0
c08/21/2019 19:44:52,03.1,01.2,105.4,41.5,0983.0
p08/21/2019 19:44:53,03.1,01.2,105.4,41.5,0983.0
p08/21/2019 19:44:54,03.1,01.2,105.4,41.5,0983.0
p08/21/2019 19:45:55,03.1,01.2,105.4,41.5,0983.0
If I restart the boron 3 more times, every line from the file would publish and have its ‘p’ replaced with a ‘c’. So the problem seems to lie in the 2nd call to this method and any subsequent calls, but the first call in the program works as intended.
If anyone can see where exactly I am making a mistake, any help would be greatly appreciated.
If anyone needs more information, please let me know and I will bring it forward. I’ve left out some code that I didn’t see as relevant, mostly network handling.
Thanks for reading
