Format and display Time on Photon

Question

I'm trying to display the current time on the OLED board attached to my Particle Photon.

void loop() {
  time_t time = Time.now();
  Time.format(time, '%Y-%m-%dT%H:%M:%S%z');
  displayString(time);
}

int displayString(String text) {
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(WHITE);
  display.setCursor(0,0);
  display.println(text);
  display.display();

  return 1;
}

I have confirmed that displayString works. As it is an embedded device, you don't have access to the regular time library, however the Photon has it's own.

https://docs.particle.io/reference/firmware/core/#time

I'm getting the error Invalid conversion from int to const char*.

Edit: For anyone else who comes across this, I discovered that while undocumented, if you do not provide a time it will use the current time, so you can just do:

String time = Time.format("%d/%m/%y %H:%M:%S");

The uppercase String type is intentional, see String class.

Someone had the same issue, the posted solution seems good : http://stackoverflow.com/questions/3053999/c-convert-time-t-to-string-with-format-yyyy-mm-dd-hhmmss — loopingz, Dec 29 '15 at 18:13
@loopingz I dont think this is the problem, given the OP's example link, this should work. The OP has made a multi-character char instead of a string though. — Fantastic Mr Fox, Dec 29 '15 at 18:18
@Ben yes sorry i haven't seen that the library Time was handling it already, my bad — loopingz, Dec 29 '15 at 18:26

score 2 · Accepted Answer · edited May 23 '17 at 11:44

2

This is likely because in this line:

Time.format(time, '%Y-%m-%dT%H:%M:%S%z');

you specify the format string as a multi-character char, not a string. Try:

Time.format(time, "%Y-%m-%dT%H:%M:%S%z"); // Note the double quotation marks

Just for some more information about multi-character chars read here: What do single quotes do in C++ when used on multiple characters?

Also pay attention to your compiler warnings, you should have received this:

warning: multi-character character constant

Which would have alerted you to this problem.

edited May 23 '17 at 11:44

Community

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answered Dec 29 '15 at 18:15

Fantastic Mr Fox

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I didn't catch that at first glance, nice eyes. – zackery.fix Dec 29 '15 at 19:02
For anyone else who comes across this, I discovered that while undocumented, if you do not provide a time it will use the current time, so you can just do: `String time = Time.format("%d/%m/%y %H:%M:%S");`. – Benedict Lewis Dec 30 '15 at 16:05

Format and display Time on Photon

1 Answers1