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I'm using a HAT that among other things has a PCF8563 real-time clock on it (fed by a supercap when the Pi is off.)

I can use i2cdetect to see the device on bus 1, but the rtc-pcf8563 module does not see it, and the i2c-rtc dtoverlay does not use it.

pi@crunch:~ $ sudo modprobe rtc-pcf8563
pi@crunch:~ $ lsmod | grep rtc
rtc_pcf8563             7056  0 
pi@crunch:~ $ sudo i2cdetect -y 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: -- 51 -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
70: -- -- -- -- -- -- -- --                         
pi@crunch:~ $ ls /dev/rtc
ls: cannot access /dev/rtc: No such file or directory
pi@crunch:~ $ grep i2c-rtc /boot/config.txt
dtoverlay=i2c-rtc,param=pcf8563
pi@crunch:~ $

I've tried the AdaFruit walkthrough and a few other web searches. From what I can tell, what I'm doing should recognize the chip, and turn it to "UU" (as in, reserved by driver) However, I can't get /dev/rtc to show up.

dmesg | grep 8563

is empty, as is

dmesg | grep -i rtc
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2
  • Aaaand just because I asked the question, the answer immediately appeared. That's why I ask questions, they make me find the answer! The answer is that I needed to "echo pcf8563 0x51 > /sys/class/i2c-adapter/i2c-1/new_device"
    – Jon Watte
    Oct 16, 2017 at 1:34
  • Also, "param=" should not be there in the dtoverlay define.
    – Jon Watte
    Oct 16, 2017 at 1:46

1 Answer 1

Reset to default
1

Change to dtoverlay=i2c-rtc,pcf8563 which is the correct syntax for Device Tree overlays.

Don't go fiddling with modprobe - Device Tree should set that up on boot.

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