Would it be possible to use the DS1302 made for Arduino?

Question

I got some spare DS1302 chips that I'd like to connect to my Raspberry Pi to use as a RTC, but I'm not so sure how to. How would I go about it?

Answer 1

Using the guide from hobbytronics as a reference, with this module i got from Cytron

1. Connect it to the RPi's GPIO

RST  (CE)  -> GPIO#17
I/O  (DAT) -> GPIO#18
SCLK (CLK) -> GPIO#21 
GND        -> GND 
VCC        -> 3v

2. compile source

http://pastebin.com/gF09XSFn

cc rtc-pi.c

this is for the rev 1 board, mine was the rev 2 so i had to update the definitions in the source:

http://pastebin.com/YJ22Sayh

#define SCLK_OUTPUT *(gpio+GPIO_SEL2) &= 0xFF1FFFFFL; *(gpio+GPIO_SEL2) |=0x00200000L
#define SCLK_HIGH *(gpio+GPIO_SET) = 0x08000000L
#define SCLK_LOW *(gpio+GPIO_CLR) = 0x08000000L

3. execute the compilation

output from the compilation would be a a.out file, rename it to rtc-pi and set the date with something like this

sudo ./rtc-pi 20131216175500

or to set it from the current time

sudo ./rtc-pi `date +"%Y%m%d%H%M%S"`

this will set the time. now all you need to do is to invoke it during every startup to keep the date

sudo ./rtc-pi

Misc

to quote the guide from hobbytronics

I also found that a pullup resistor is needed between DAT and VCC (= 3.3V). A 10k..30k resistor seems to work fine.

Now i didn't do this at the moment because i don't have any resistors with me, not so sure about the impact of it.