http://www.waveshare.com/wiki/MISC_CAPE
One of the links turns out to be to two SD card images, one of which is a fully compiled Debian image that has the drivers for the PCF8563 chip built in, however when I downloaded and tried it I found that although the RTC driver seemed to work well there were other issues with the distro that have to be overcome:
http://www.waveshare.com/wiki/MISC_CAPE_Image
There are other links on the same wiki page that I'm still trying to figure out. The "User Manual" link is just to a PDF of the wiki. The Schematic is helpful but really the cape is quite simple and the schematic is a single page. The Test Code link is to a zip file named XXX_CAPE_Angstrom_API.7Z which seems to contain a mix of C programs and compiled programs which don't have anything to do with the PCF8563 and furthermore seem to be for the Angstrom kernel. The section labelled "Kernel" seems to have several different source code trees for both Angstrom and Debian kernels, presumably with driver code but at the moment I still don't know how my way around kernel source code or how to compile kernels although it looks like I'm going to have to learn. The section labeled "Kernel_config" also seems to have to do with compilation so I will have to become smarter to even understand what it is. I have absolutely no idea what the link labelled "Cross-compilation toolchain" is even referring to. Under Source Code there are several links to zip files but some obviously have nothing to do with the RTC chip (like "wifi" and "mjpg-steamer") and the one link labelled "driver" is to a zip file that just has one c file with code that also doesn't seem to have anything to do with the RTC chip. Of the three links under "Documentations" the first one "Porting Drivers" actually mentions the RTC chip but the compilation instructions are like greek to me. The link for "Porting Kernel" mysteriously seems to be about building a Ubuntu kernel, and these instructions are also opaque to me at the moment.
Looking for a shortcut to figuring out the poorly documented materials on the Waveshare wiki, I started looking at the following tutorial, which showed how to interface a different chip that is on Adafruit's RTC stamp to BeagleBone.
https://learn.adafruit.com/downloads/pdf/adding-a-real-time-clock-to-beaglebone-black.pdf
Since I also bought one of those Adafruit RTC stamps, I may yet give following this tutorial as written a try, but I thought that I could adapt the steps shown to the PCF8563. I tried doing the i2cdetect command and it found the PCF8563 at its address of 0x51. I did the command to add it as a new device and that seemed to go okay. There was an rtc0 device in /dev that I was able to write a time to and read from. I went through all the rest of the steps to set up a service to read from the rtc at bootup but whenever I power cycled the BeagleBone it would come up with a default date which was March 1, 2013.
I realized that something was writing time to the rtc, and went through a bunch of research to discover that there is a hwclock.sh script that is being called by several different boot levels in Debian that seems to be setting this default time to rtc0. The hwclock.sh script is at /etc/init.d/; the directories /etc/rcS.d/, /etc/rc0.d/, and /etc/rc6.d/ all seem to have the same script also but these are really just sim links to the one in /etc/init.d/. The other directories are used to define init scripts called at different kernel boot levels. This information is all swirling around inside the following comment thread:
https://www.raspberrypi.org/forums/viewtopic.php?f=44&t=16218
I tried modifying this hwclock script as advised in the thread but didn't have any luck. I began to realize from reading the script and the messages in /var/log that the rtc0 device was some kind of default device and not the PCF8563 chip on my Waveshare cape after all. I tried doing modprobe commands as shown in the link above and in some other links I found and it seems like the rtc-pcf8563 "module" is something that I need and don't have and which should run when I add the chip as a new device on the I2C bus. I found some .ko files on my Debian system under /lib/modules/3.8.13-bone70/kernel/drivers/rtc but none of them are rtc-pcf8563.ko or rtc-ds1307.ko either for that matter.
A frequent hit that I keep getting while googling for the problems I am having installing this cape is the following site in what seems to be Hebrew or something. Without using Google Translate, I can tell that he's going through all the same steps that I did, using i2cdetect, adding it as a new device, and creating a service to load the system time from it a bootup. However, when he uses dmesg to check his log files after adding the device, he sees the "chip found" message that I'm not getting. I need to look at this site more carefully to understand what OS and distro he is using; if there's a chance he's using Debian it might give me a clue:
http://www.boonsanti.com/setting-a-real-time-clock-to-beaglebone-black-with-rtc-pcf8563/
Here's a listing for a Debian distribution that shows an rtc-pcf8563.ko file in the right place, but clearly this isn't my distribution. I need to find out the chances are that I can just find one of these .ko files and copy it onto my system (probably not great):
https://packages.debian.org/squeeze/armel/linux-image-2.6.32-5-versatile/filelist
Along the way as I did this research, I've learned that there is something called "fake-hwclock" which maintains current time in nonvolatile memory and reloads it during bootup, but I don't have that on my system. Here's a link with some info:
http://unix.stackexchange.com/questions/187261/automatically-update-hwclock-at-boot
I learned that Debian has a very nice editor called "nano" that has keyword color support and is easy to use (though not as easy as vi of course)
To edit system files, I had to change from the default login of user 'debian' to root, but when I tried "su root" it asked for a password. Various sites said that this distro had no password for root, but just hitting return on the password prompt wasn't working. I learned from the following page that I need to do "sudo su" to become root on this system:
http://www.element14.com/community/thread/32106/l/beagleboardorg-releases-debian-for-beaglebone-black?displayFullThread=true
I think that my system is using systemd instead of init. Here is what looks like nice info on systemd:
https://denibertovic.com/posts/setting-up-systemd-on-debian-in-10-minutes/
There's a book called "BeagleBone For Secret Agents" that had a google books excerpt that helped me better understand that rtc0 was not my cape, that it's an rtc inside the processor that doesn't retain time when powered off. It showed messages from a process named omap_rtc that was loading the default time and I was able to find those same messages on my system showing it setting the default clock to March 1, 2013. Here's the link to the google books excerpt:
https://books.google.com/books?id=i2OZBAAAQBAJ&pg=PT130&lpg=PT130&dq=omap_rtc+setting+system+time&source=bl&ots=9hLmjeWaPe&sig=j3ScuHRzYYN2Un2ljn_0gbsglgs&hl=en&sa=X&ved=0ahUKEwie9MXq5anKAhUIPT4KHZ6XB60Q6AEIJjAB#v=onepage&q=omap_rtc%20setting%20system%20time&f=false
Here's a blog by a guy who had a problem very similar to mine. He had an RTC chip that there was no module for in the distribution of Raspian that he had. He found drivers and compiled them and verified that the resulting module detected his chip. I need to carefully study this link to understand all of his steps and maybe try the same thing for my kernel and chip:
http://blog.remibergsma.com/2013/05/08/adding-a-hardware-clock-rtc-to-the-raspberry-pi/
When I google for drivers for the PCF8563, I usually get the following link, which interestingly is from a BeagleBone site so it seems that compiling this for BeagleBone is something that is done, although there don't seem to be any instructions or compiled module files at this link:
https://github.com/jeffegg/beaglebone/blob/master/drivers/rtc/rtc-pcf8563.c
Here's a guy interfacing a PCF8563 to a raspberry pi, and for some reason his kernel has the driver module already there. He does a modprobe command on rtc-pcf8563 and it works, so he goes merrily along with the rest of his installation steps.
http://www.susa.net/wordpress/2012/06/raspberry-pi-pcf8563-real-time-clock-rtc/
Some links to stuff that I found which didn't directly help but I'm saving just in case:
Here's a hackaday article on the PCF8563 which goes into accessing its registers and stuff without showing any kind of finished code. Interesting, but I hope I never have to use it: http://hackaday.com/2009/06/26/parts-i2c-real-time-clock-calendar-pcf8563/
Here's a raspberry pi forum where some people are digging into the source code to find out why the rtc interface for the PCF8563 doesn't work for the PI2. Not useful to me but crazy smart: https://www.raspberrypi.org/forums/viewtopic.php?f=28&t=100132
Here's setup documentation for an expansion board for the pi that uses the PCF8563. It shows the "chip found" message that I should be seeing in my logs but am not. I wish my RTC cape had this kind of documentation: https://ludwig.im/en/projects/raspberry-pi/raspberry-pi-arpi600
It turns out that Waveshare makes another RTC board with a PCF8563 for a different kind of stamp computer development system. This information wasn't helpful however because the documentation for this other RTC board included no drivers compatible with the BeagleBone: http://www.waveshare.com/pcf8563-rtc-board.htm
