Arduinoos

RTC Module (Part 5)

Posted on 25 May 2011, 12:10, by Didier, under Clocks, Hardware.

Part 1, 2, 3, 4, 5, 6, 7

In the previous posts, I described a MAXIM DALLAS DS1306 based module which proved to be easy to set up and to program. However, the DS1306 has one major drawback (and a minor one) which really puzzled me while wiring multiple SPI devices on the same port. Two from the four SPI modes are supported by the DS1306 RTC chip: mode 1 (CPOL=0, CPHA=1) and mode 3 (CPOL=1, CPHA=1). While most SPI devices support mode 0 and 2: too bad. In addition, the chipselect pin works in high true mode, while most SPI devices are wired in ground true logic.

These differences can generate a lot of trouble while writing interlaced SPI controls. Fortunately, MAXIM DALLAS released a fancy tiny (too tiny!) RTC which is similar (with some differences) to the DS1306. Here is a picture of the pair of samples which were very kindly sent by MAXIM DALLAS in less than a week (Thank you again M.D.)

As you can see, the chip fits in μSOP packages, which is a problem for prototyping it! Here is a description of a small and cheap adaptator.

Firstly, prepare a printed circuit: cut it and degrease it. Glue the chip in the middle of the printed circuit:

Solder two headers of 5 pins at the back of the printed circuit, just like this

Now comes the hard time. Solder each pin from the chip to a header tip. For this, a good iron solder (0.5 mm tip) and a spy glass are required. Here comes the result