ds3231 clock temperature sensor access?

[darkbibble]

according to the spec sheet for the ds3231 clock it has a internal temprature sensor. is there any way to access this via the i2c??

[DougieLawson]

What does i2cdetect -y 1 show?
What does ls -la /sys/bus/i2c/devices/1-0068/* show? There might be a pseudo filesystem file there for the temperature sensor registers.

[darkbibble]

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 pi@pi-top:~ $ i2cdetect -y 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- 0b -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
60: -- -- -- -- -- -- -- -- UU -- -- -- -- -- -- -- 
70: -- -- -- 73 -- -- -- --                         
pi@pi-top:~ $ ls -la /sys/bus/i2c/devices/1-0068/*
lrwxrwxrwx 1 root root    0 Mar 27 15:32 /sys/bus/i2c/devices/1-0068/driver -> ../../../../../../bus/i2c/drivers/rtc-ds1307
-r--r--r-- 1 root root 4096 Mar 27 15:32 /sys/bus/i2c/devices/1-0068/modalias
-r--r--r-- 1 root root 4096 Mar 27 15:32 /sys/bus/i2c/devices/1-0068/name
lrwxrwxrwx 1 root root    0 Mar 27 15:32 /sys/bus/i2c/devices/1-0068/of_node -> ../../../../../../firmware/devicetree/base/soc/i2c@7e804000/ds3231@68
lrwxrwxrwx 1 root root    0 Mar 27 14:09 /sys/bus/i2c/devices/1-0068/subsystem -> ../../../../../../bus/i2c
-rw-r--r-- 1 root root 4096 Mar 27 14:09 /sys/bus/i2c/devices/1-0068/uevent

/sys/bus/i2c/devices/1-0068/power:
total 0
drwxr-xr-x 2 root root    0 Mar 27 15:32 .
drwxr-xr-x 4 root root    0 Mar 27 14:09 ..
-rw-r--r-- 1 root root 4096 Mar 27 15:32 autosuspend_delay_ms
-rw-r--r-- 1 root root 4096 Mar 27 15:32 control
-r--r--r-- 1 root root 4096 Mar 27 15:32 runtime_active_time
-r--r--r-- 1 root root 4096 Mar 27 15:32 runtime_status
-r--r--r-- 1 root root 4096 Mar 27 15:32 runtime_suspended_time

/sys/bus/i2c/devices/1-0068/rtc:
total 0
drwxr-xr-x 3 root root 0 Mar 27 15:32 .
drwxr-xr-x 4 root root 0 Mar 27 15:32 ..
drwxr-xr-x 3 root root 0 Mar 27 14:09 rtc0
 

[DougieLawson]

What did you add to /boot/config.txt for your RTC?

Anything more in /sys/bus/i2c/drivers/rtc-ds1307/*

[gregeric]

DS3231 temperature sensor readout is in kernels >=4.6 AFAICR

[darkbibble]

Code: Select all

 # turn real time clock on
dtoverlay=i2c-rtc,ds3231
gpu_mem_256=128
gpu_mem_512=256
gpu_mem_1024=256
overscan_scale=1
dtparam=i2c1=on
dtparam=i2c1_baudrate=50000
 

pi@pi-top:/sys/bus/i2c/drivers/rtc-ds1307 $ ls
1-0068 bind module uevent unbind

[DougieLawson]

OK, so it looks like the kernel driver in the RPF kernel doesn't support reading the temperature registers from your ds3231.

Sorry, I can't fix it for sure. I don't have a ds3231 handy. Try sudo rpi-update to get the 4.9 kernel.

[gregeric]

Or, cherry pick the newer rtc-ds1307.c source and build & replace rtc-ds1307.ko. That's what i did. Let me know if you need a quick run down on that.

[DougieLawson]

Or, cherry pick the newer rtc-ds1307.c source and build & replace rtc-ds1307.ko. That's what i did. Let me know if you need a quick run down on that.

rpi-update to 4.9.17 is probably safer for a general user in this case, building kernels isn't for the faint hearted. I know we don't usually recommend rpi-update but this is one case where jumping from 4.4.50 to 4.9.17 may solve the OP's problems.

Twelve out of fourteen of my raspberries are running 4.9.17 so we can assume it's relatively safe and won't turn the OP's RPi into a brain-dead corpse that won't boot.

[gregeric]

Build the module alone, not the entire kernel. I have a simple recipe for that, will post it later.

[gregeric]

So, to build only the required rtc-ds1307.ko to get DS3231 temperature support in kernels <4.6.

Firstly, get kernel header files:

Code: Select all

sudo apt-get update && sudo apt-get dist-upgrade
sudo apt-get install -y raspberrypi-kernel-headers
sudo reboot

After reboot,

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mkdir ds1307
cd ds1307
wget https://raw.githubusercontent.com/raspberrypi/linux/rpi-4.9.y/drivers/rtc/rtc-ds1307.c
nano Makefile

Makefile contents (indent is a single <tab>, not spaces):

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obj-m := rtc-ds1307.o
ccflags-y += -DCONFIG_RTC_DRV_DS1307_HWMON

all:
	make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules

clean:
	make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

install:
	sudo cp rtc-ds1307.ko /lib/modules/$(shell uname -r)/kernel/drivers/rtc/
	sudo depmod -a

Backup old module, build & install:

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sudo cp /lib/modules/$(uname -r)/kernel/drivers/rtc/rtc-ds1307.ko /lib/modules/$(uname -r)/kernel/drivers/rtc/rtc-ds1307.ko.bak
make clean all install
sudo reboot

Test the sensor:

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sudo apt-get install -y lm-sensors
sensors

Output should be something like this:

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ds3231-i2c-1-68
Adapter: 20804000.i2c
temp1:        +20.8°C

[darkbibble]

thanks, i did "sudo rpi-update" to update kernal, then installed the sensor module,

works great