DS1307 W RPI Wheezy Softfloat

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March 22, 2013 at 6:52 pm #22376
pauldy
Participant
I have the OpenSprinkler PI setup at home and tried to get the RTC working. I can see it registered on the i2c bus and the appropriate kernel modules are loaded but I can’t seem to read the clock. Any pointers? I’ve included what I believe to be relevant output to show what I’m able to see here.
```
#i2cdetect -y 0

0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f

00:          -- -- -- -- -- -- -- -- -- -- -- -- --

10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --

20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --

30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --

40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --

50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --

60: -- -- -- -- -- -- -- -- UU -- -- -- -- -- -- --

70: -- -- -- -- -- -- -- --
```
```
#lsmod

Module                  Size  Used by

bnep                   10514  2

rfcomm                 33663  0

bluetooth             157711  10 rfcomm,bnep

binfmt_misc             6888  1

snd_bcm2835            12808  0

snd_pcm                74834  1 snd_bcm2835

snd_seq                52536  0

snd_timer              19698  2 snd_seq,snd_pcm

snd_seq_device          6300  1 snd_seq

snd                    52489  5 snd_seq_device,snd_timer,snd_seq,snd_pcm,snd_bcm2835

snd_page_alloc          4951  1 snd_pcm

rtc_ds1307              6710  0

i2c_dev                 5587  0

spidev                  5136  0

8192cu                485042  0

i2c_bcm2708             3681  0

spi_bcm2708             4401  0
```
```
#hwclock -r

hwclock: ioctl(RTC_RD_TIME) to /dev/rtc0 to read the time failed: Invalid argument
```
```
#cat /sys/class/rtc/rtc0/time

cat: /sys/class/rtc/rtc0/time: Invalid argument
```
March 23, 2013 at 3:50 pm #23445

Ray
Keymaster

A while back Dan in CA sent me some instructions on how to use RTC with RPi. I tried and they seem to work. I’m posting his instructions here, hope these help:

FYI
after a few different iterations, here are the settings I used to access the RTC:

1. added following lines to /etc/modules (sudo nano /etc/modules)
i2c-bcm2708
rtc-ds1307
2. added following line to /etc/rc.local
echo ds1307 0x68 > /sys/class/i2c-adapter/i2c-0/new_device

3. Reboot

must be root or use sudo: hwclock -r to read clock.
set the hardware clock from the current system time: hwclock -w
set the system time from the hardware clock: hwclock -s

Following up on the RTC stuff:

You must ‘sudo -s’ before you can set the RTC.

March 23, 2013 at 3:54 pm #23446

Ray
Keymaster

Another useful resource is the RTC for RPi tutorial by adafruit:
http://learn.adafruit.com/adding-a-real-time-clock-to-raspberry-pi/overview

March 23, 2013 at 4:43 pm #23447
pauldy
Participant
I actually figured it out late last night. According to the man page it doesn’t really make sense the -s is supposed to sync the system clock form the hwclock but the following is form my terminal session and it solved the invalid argument. I really just ran these out of desperation as I had already been poking around reading the NVRAM on the ds1307 and knew it was at least communicating with the device.
```
hwclock: ioctl(RTC_RD_TIME) to /dev/rtc0 to read the time failed: Invalid argument

#hwclock -w

hwclock: ioctl(RTC_RD_TIME) to /dev/rtc0 to read the time failed: Invalid argument

#hwclock -s

#hwclock -r

Sat 22 Mar 2013 11:34:45 PM CDT  -0.925138 seconds

#cat /sys/class/rtc/rtc0/time

4:34:49
```
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