I am currently working on a device that logs incoming phone calls, and sends data to me via text message. I am using a Seeeduino Stalker v2.3 and a SIM 900 GPRS Shield v1.4.
One of the reasons I use the Stalker is because of it's nifty onboard Real Time Clock, which works great. I've also mastered controlling the GPRS Shield pretty well.
Yesterday I was unpleasantly surprised when I tried to use the two simultaneously. The GPRS Shield somehow prevents I2C communication with the RTC.
Here they claim I can simply cut the SDA and SCL pins, and it will sort out the problem. Apparently the shield doesn't use these pins at all. Is this true?
Before I perform irreversible surgery on my GPRS Shield, I'd like to have some more experienced opinions.
My Stalker and Shield are both newer versions than mentioned in the above website.
Note: A4 and A5 are connected to the I2C pins on the SIM900. The SIM900 however cannot be accessed via the I2C .
Yes, it would make sense to me that you would disconnect those pins. I would suggest that instead of cutting any traces that you simply cut/desolder/remove the A4/A5 pins from the GPRS shield. Two little snips and you're done, and if for some unknown reason you need them back you can replace them.
Before I bent away these pins, I used them to check if the shield was on. I don't know why it worked, but it did. Now I need a new way to check if the shield is on. Any suggestions?
I have connected pin 17 ( D17(A3) ) to the Uart pin R1 (or RI? I can't see) with a 10k resistor. Now I can read pin 17 for a power status (the pin goes high when the shield comes on).