Oxford CWM Team


A team for the Oxford Engineering Coursework Module

Tiny_RTC

A page collecting stuff relating to the Tiny RTC arduino module.

pcb

This board has two i2c devices on board.. a maximum DS1307 realtime clock and an amtel A24C32 32kb Eeprom. Some apparetnly alos come with a DS18B20 1 wire thermometer as well but most of the ebay variety don't, having three holes in the pcb to wire them to.. if you have one..

/media/uploads/cstevens/ds1307ckt.jpg

The Ds1307 runs at 100kbps whilst the A24C32 an do 400kbps.

Both are on the same bus lines with common pullup resistors on board of 3.3k.

The address for the DS1307 (RTC) is 0x1101000r whilst the A24C32 Eeprom is 0x1010xxxr where xxx are three bits set by address lines A2-A1. r is the read or write bit where r=0 to write to the slave (mbed is the master, peripherals are the slaves) and r=1 to read from it.

On the tiny RTC these address lines are all set to 0 so we have the EEprom address as 0x1010000r where r is the read / write bit determining the operation.

To use this device one needs to connect as follows (pin names for the KL25Z)

Tiny RTC pinmbed pinfunction
DSn/cdata for 1 wire thermometer if present
SCLI2C SCLI2C clock
SDAI2C SDAI2C Data
VCC5Vmust be 5V
GND0Vany gnd

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