Hi guys, trying to make a clock from this shield.
https://www.sparkfun.com/products/11849
I also have RTC Module: https://www.sparkfun.com/products/retired/99 - which has in the schematics use for pins Analog 4/5 - but I am almost sure these are already taken for the 7 Segment shield.
Which ports are free on that 7-segment shield so I can connect the RTC module.
Thanks 
The RTC is an I2C peripheral. Unless you want to write your own I2C routines, SDA and SCL on the RTC must connect to SDA and SCL on the processor. Looking at the schematic for the shield, SDA and SCL connect to pins A4 and A5 on the shield connector, and are not otherwise used on the shield. So connect the two and you will be fine. You will have to change the code on the onboard processor. Alternatively, plop the shield on an arduino, wire the RTC to SDA and SCL as well, and run your code on the arduino.
/mike
n1ist:
…Looking at the schematic for the shield, SDA and SCL connect to pins A4 and A5 on the shield connector, and are not otherwise used on the shield…
This shield can communicate via TTL serial, I2C or SPI to the host Arduino board. SDA/SCL are connected to pins 27+28 on the processor, apparently for the purpose of I2C communication with the host board.
As long as the RTC and Shield have different I2C bus addresses (likely so) they should be able to coexist on the same I2C bus. Otherwise, you’ll have to bit-bang an I2C interface on some other digital pins, as n1ist stated. There are a few software I2C libraries out there for this purpose.
[edit]
My assumtion above is that the Arduino Host is the I2C master and the shield is configured as an I2C slave device.
Thank you guys, so I will give it a try to connect RTC to A4-A5 anyway and try the code. I was wondering why the 7-Segment has 3 ways to communicate SPI , Serial and IC2 - this way I am wondering which one is best to use. But I guess in my case there is no matter.
Will test it now and report later.
Just finished the tests - ALL WORKS FINE !
A4 and A5 are connected to RTC module. I am using Serial communication to 7-Segment because only there I found way to control the dots.
So far I have working clock + Temperature and Humidity sensor attached on digital pin 5 [RHT03.
I guess I can write details in new thread for the whole build.
Thanks again for the help :doh:](Humidity and Temperature Sensor - DHT20 - SEN-18364 - SparkFun Electronics)
Glad to hear it worked.
Leave a bread crumb here for others. Post a link here when you do your build thread.