mcp79410

[DavidCozens]

I want to get the mcp79410 RTC on the UniPi add on board functional with Raspbain Jessie. When I have completed installation and I reboot, the hw clock seems to loose the time - I get the following

sudo hwclock -r
hwclock: The Hardware Clock registers contain values that are either invalid (e.g. 50th day of month) or beyond the range we can handle (e.g. Year 2095).

I have found several useful posts on the issues I'm seeing but nothing that gives a convincing solution. To make it really easy to reproduce I have created a shell script (below) that performs my entire configuration. Following a clean install of the March release of Rasbian Jessie, I run raspi-config and expand the disk image, copy on the script below, run the script as root, reboot.

Code: Select all

#!/bin/bash
# UniPi RTC driver setup

if [ "$EUID" -ne 0 ]
    then echo "This script must be run as root"
    exit
fi

echo Backup files
cp /boot/config.txt /boot/config.txt.bak
echo Enabling I2C bus...

if ! grep -q '^dtparam=i2c_arm=on' /boot/config.txt
    then echo 'dtparam=i2c_arm=on' >> /boot/config.txt
fi

if ! grep -q '^dtparam=i2c_baudrate=400000' /boot/config.txt
    then echo 'dtparam=i2c_baudrate=400000' >> /boot/config.txt
fi
echo Enabling the RTC chip...
if ! grep -q '^dtoverlay=i2c-rtc,mcp7941x' /boot/config.txt
    then echo 'dtoverlay=i2c-rtc,mcp7941x' >> /boot/config.txt
fi

echo Getting i2c development tools
apt-get install -y i2c-tools
if ! grep -q '^i2c-dev' /etc/modules
    then echo 'i2c-dev' >> /etc/modules
fi

echo Removing fake-hwclock...
apt-get purge -y fake-hwclock
update-rc.d -f fake-hwclock remove
apt-get autoremove -y

echo ' '
echo 'CODESYS for UniPi installed.'
echo ' '
echo '!!! REBOOT IS REQUIRED !!!'
echo ' '

read -p "Is it OK to reboot now? [y/N] " -n 1 -r
echo ' '
if [[ $REPLY =~ ^[Yy]$ ]]
then
    reboot
else
  echo 'Reboot to finish configuring drivers'
fi
echo ' '

NOTE: There is a battery fitted - but I see the issue without removing power - sudo reboot is sufficient to loose the time..
NOTE: The hw clock can be seen to be functional - before rebooting I can write and check the clock like this

sudo hwclock -w
sudo hwclock --debug
hwclock from util-linux 2.25.2
Using the /dev interface to the clock.
Last drift adjustment done at 1460323428 seconds after 1969
Last calibration done at 1460323428 seconds after 1969
Hardware clock is on UTC time
Assuming hardware clock is kept in UTC time.
Waiting for clock tick...
/dev/rtc does not have interrupt functions. Waiting in loop for time from /dev/rtc to change
...got clock tick
Time read from Hardware Clock: 2016/04/10 21:23:59
Hw clock time : 2016/04/10 21:23:59 = 1460323439 seconds since 1969
Sun 10 Apr 2016 21:23:59 UTC -0.724333 seconds

Any help is really appreciated. My target is to have all required setup in a single script.