I'm using a SM5100B shield and it works great ON the Arduino. For packaging considerations, I'm trying to move the shield off the Arduino and use jumpers but it's being buggy.
What are the required connections between the Arduino and Shield? So far I have:
5V, all three GNDS, Reset pin, and the TX0/RX0 connections. What am I missing?
Look at the schematic: http://www.sparkfun.com/datasheets/DevTools/Arduino/cellular%20shield-v12.pdf
It uses Vin, not 5V, and has an onboard regulator. I'm surprised it works if the Arduino is running of USB power instead of Vin.
It also has the option to use D2 and D3 instead of RX (D1) and TX (D0).
I currently have the shield stacked on the Arduino with a regulated external 5V, 2.5A power supply going into the 5V and GND pin on the shield.
If I run a 5V and GND rail to the shield the power LED lights up..but the schematic only indicates that Vin is a voltage input..
I'm still having trouble running this shield OFF the board though.
So based on the schematic I need to run a jumper from reset to GND also?
I'm surprised that it works without power on Vin. Perhaps the shield does not match the schematic, in which case all bets are off. Take a careful look at the shield to see if the pins that are connected are the ones shown in the schematic.
If you add a jumper from Reset to Ground it will be like holding down the Reset button and NOTHING will work.
I would try a wire from Vin on the shield to 5V on the Arduino. That should be enough to power the 3.3V regulator.