PiFace RTC on Raspberry Pi2: still losing time on reboot!

You may have done this already but...

without any script to talk to the RTC on power up

set the RTC time manually using one of the above commands

read the time back from the RTC... is it correct

now without any automated scripts talking to the RTC reboot the PI, and remember... no scripts should be talking to the RTC during power up either

once booted, again read (Only Read) the time back out of the RTC, it should be correct or very close as you have not powered off the device irrespective of the battery

if this worked, shutdown the pi and dissconnect the power to the PI, wait a few seconds and power up again, now read the RTC again... again no other scripts should be going near the RTC

If this also reads correctly or within a few seconds, then you issue is with your scripts in the auto start up.

If this does not work then you probably have hardware issues

Hi Peter,

a strange thing happens.

I set the date with

sudo date -s ...

I write the RTC with

sudo hwclock -w

Read the time with

sudo hwclock -r

And it gives me the correct time.

Now I shoutdown and I wait for few minutes.

I boot up, I read the RTC with

sudo hwclock -r

and the time is OK.

Now I reboot (without shutting down) with

sudo reboot

Once booted, I read the RTC:

sudo hwclock -r

The correct time doesn't appears, it give me the error message:

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).

How can the RTC be correct after a shoutdown / powerup and not correct after a simple reboot? Who is that set the date to an invalid range value?? There should be somewhere some wrong stuff that is involved at the startup.. really cannot understand where!

Many thanks!

Andrea

Added:

I don't believe this can be the issue (because the i2c is well detected), but I noticed that in the /boot/config.txt I have a dtparam=i2c=on; shouldn't it be dtparam=i2c1=on?

I noticed one thing.

When the RTC is not read well, during the boot I can read an error message on the screen, please see the image provided:

It seems to involve the /etc/rc.local. Perhaps is there an issue in such file?

My /etc/rc.local is below. Is there something wrong inside it?

!/bin/sh -e 
# 
# rc.local 
# 
# This script is executed at the end of each multiuser ru$ 
# Make sure that the script will "" on success or any oth$ 
# value on error. 
# 
# In order to enable or disable this script just change t$ 
# bits. 
# 
# By default this script does nothing. 

# Print the IP address 
_IP=$(hostname -I) || true 
if [ "$_IP" ]; then 
  printf "My IP address is %s\n" "$_IP" 
fi 

# Calibrate the clock (default: 0x47). See datasheet for $ 
i2cset -y 1 0x6f 0x08 0x47 
modprobe i2c:mcp7941x 
echo mcp7941x 0x6f > /sys/class/i2c-dev/i2c-1/device/new_$ 
hwclock -s

Thanks again,

Andrea.

I would not be surprised if the driver takes a second before it has the chip up-and-running. So I would place a "sleep 1"  before the "hwclock -s".

Does that help?

Unfortunately it does not help !

Does 'man hwclock' provide any insight, it appears to have various routes to accessing the RTC.  My Pi returns "Cannot access the hardware clock by any known method" but I'd expect this because I haven't added a system driver.  I do however have an off-board circuit to drive a DS1337 via I2C.  For this I have used Gordon's WiringPi but if the truth were known I haven't yet resolved the time discrepancy with that. Too many things to do...

is there any way of pinging the time off the internet to reset? using the time.windows.com server ?

yes, use the NTP... Network Time Protocol

After reading this and a couple of similar posts, I decided to try hooking up a similar device, the DS 1307, in the same manner. I wrote a blog about it here

Enabling RTC on the Raspberry Pi 2

Mike

Michael Conners ha scritto:

 

After reading this and a couple of similar posts, I decided to try hooking up a similar device, the DS 1307, in the same manner. I wrote a blog about it here

 

Enabling RTC on the Raspberry Pi 2

 

Mike

Thanks Mike, this is very interesting and well described! My rtc device has a MCP7940N onboard. Can I ask you which particular RTC commercial board with the DS1307 did you used in your guide?

laser srl wrote:

 

Thanks Mike, this is very interesting and well described! My rtc device has a MCP7940N onboard. Can I ask you which particular RTC commercial board with the DS1307 did you used in your guide?

I tried to figure out the manufacturer the other day and I can not remember where I purchased it. There is a good chance it's a Chinese board I bought from ebay. Adafruit sells a kit, but I'm not sure where the best source for you would be in Europe.

Mike

Looking at your post above, I noticed one of the lines in your rc.local has

1. echo mcp7941x 0x6f > /sys/class/i2c-dev/i2c-1/device/new_$  

does it really have a $ at the end? Is that valid? The examples I've seen, and a code snippet I found for the I2C driver, said new_device

in fact in my example on my blog post, I had

echo ds1307 0x68 > /sys/class/i2c-adapter/i2c-1/new_device

notice, there is a difference

/sys/class/i2c-adapter

vs

/sys/class/i2c-dev

although I see that both exist on my pi

I'd also consider commenting out the calibrate line in the rc.local

Mike

Looking at your post above, I noticed one of the lines in your rc.local has

1. echo mcp7941x 0x6f > /sys/class/i2c-dev/i2c-1/device/new_$  

does it really have a $ at the end? Is that valid? The examples I've seen, and a code snippet I found for the I2C driver, said new_device

in fact in my example on my blog post, I had

echo ds1307 0x68 > /sys/class/i2c-adapter/i2c-1/new_device

notice, there is a difference

/sys/class/i2c-adapter

vs

/sys/class/i2c-dev

although I see that both exist on my pi

I'd also consider commenting out the calibrate line in the rc.local

Mike