DS1307 not detected by i2cdetect

balenaFin
1

I have the following setup:

  • BalenaFin v1.1 with CM3+ lite attached
  • RTC battery (fresh, measured 3.24V) placed in its socket
  • flashed Raspbian Stretch (using Balena Etcher)
  • I2C activated in raspi-config -> Interfacing Options -> I2C
  • last line of /boot/config.txt is “dtoverlay=i2c-rtc,ds1307”

However, the output of “sudo i2cdetect -y 1” still shows that there is no I2C device.
Other I2C devices (for example an ADS1115 a/d-converter) are seen by i2cdetect (after connected to the I2C pins), so I guess the I2C bus itself is working.

I also tried flashing the following operating systems and got the same result:
Raspbian Jessie
Raspbian Buster
Raspbian (balena version from https://www.balena.io/fin/1.1/docs/downloads/)

Am I missing something?
Is there any way to tell if the RTC module is working/broken?

Any help would be appreciated.

// Philipp

5

Hi and welcome to the forums!
You could try using the timedatectl utility: if that shows the RTC output, then RTC is working.
More info on that here
Tell us if this solves your issue or if you need anything else!

7

Hi,
the ouput of timedatectl on Raspbian Stretch says RTC time: n/a.

If I flash the balena-preconfigured Raspbian, timedatectl says RTC time: Wed 2019-07-17 05:17:47.
The command i2cdetect -y 1 still indicates that no I2C device is found, but the RTC seems to work.

This would mean that some configuration step is missing on Raspbian Stretch apart from these:

  • I2C activated in raspi-config -> Interfacing Options -> I2C
  • last line of /boot/config.txt is “dtoverlay=i2c-rtc,ds1307”

Can anyone give me a hint what I am missing?

8

Hi,
just made it work. Here is my setup now:

  • BalenaFin v1.1 with CM3+ lite attached
  • RTC battery (fresh, measured 3.24V) placed in its socket
  • flashed Raspbian Stretch (using Balena Etcher)
  • I2C activated in raspi-config -> Interfacing Options -> I2C
  • added to /boot/config.txt: “dtoverlay=balena-fin”
  • added to /etc/modules: “rtc_ds1307”

Why it didn’t work:

  • I assumed that the DS1307 was on i2c-1 (as described on https://learn.adafruit.com/adding-a-real-time-clock-to-raspberry-pi/set-rtc-time). Instead, the RTC is on i2c-3, which is not available without using “dtoverlay=balena-fin”.
  • Adding “dtoverlay=i2c-rtc,ds1307” does not load the module “rtc_ds1307”. Without that, “timedatectl” does not give an RTC output. I had to load the module explicitly in /etc/modules

Thanks for the hint with timedatectl, that led me on the right track.

Greetings

// Philipp