Teensy 3.2 and ChronoDot 2.1

[Vincefarq]

Hi folks,

I'm trying to wire a ChronoDot 2.1 to a Teensy 3.2 and having a hard time of it. I'm following the suggestions in this Teensy 2++ thread, keeping in mind the 5v/3v difference:
https://forum.pjrc.com/threads/1045-ChronoDot-(Adafruit)-use-with-Teensy-2

Here's a photo of my wiring:


Am I doing something wrong here? Will the ChronoDot even take 3v? I've got 2.2K resistors on the SDA and SCL signals.

When I run the File > Examples > DS1307RTC > ReadTest example (from https://www.pjrc.com/teensy/td_libs_DS1307RTC.html) it fails to detect the RTC:

DS1307 read error! Please check the circuitry.

Can someone please send me a clue?

Thanks!

-Vince

 

[MichaelMeissner]

Your wiring is messed up. You have the resistors between the Teensy's SDA/SCL and the Chronodot.

Instead what you need to do is remove the two resistors. Then either plug the green wire directly into the row with the SDA port, and the yellow wire directly into the row with the SCL port, or if you want to keep them in the 2nd power lines, run jumper cables from the appropriate power line to SDA and SCL.

Then take one of the resistors, and plug one end into the row A4/SCL/18 is on, and plug the other end into the 3.3v power line (red). Do the same for the A5/SDA/19 row. This is what is called a pull-up resistor (one end is plugged into the power source, and the other end is plugged into the data pin).

The other type of resistor setup is called a pull-down resistor, where you plug the resistor between ground (black) and the data pin. You don't use that in this example.

In this picture from the DS1307RTC library page:

You can see the two resistors being connected from pins 18 and 19 to the power port, and two white wires also connecting 18/19 to the SCL/SDA pins of the chip.

 

[Vincefarq]

Wow. I totally saw that in the thread but it didn't register. Thank you so much!

It works. Posting my wiring so future ppl may benefit from my issues.



-Vince