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I have a Raspberry Pi 2B and a SM900 module and I want to make a UART connect with jumpers using raspberry GPIO and the shield pins.

My problem is how could I make it? How to power up the SM900? I have a desk external energy supply, but the shield doesn't clearly identify the pins. I read that if a wrong connection is make, it damages the shield and I don't have another one to use.

My Pi uses Raspbian Jessie and I want to use Python, because in future I make a REST service with Python too.

  • Beware that many of these things work on an odd voltage, unless you are a cellphone (3.4-3.7 V). Make sure you are certain one way or another what supply voltage it wants and what logic level it uses (they may not be the same). If it is all 3.7 V, you will need a step down converter for power and a level shifter for logic. Don't try and connect anything until you know the answers to those questions. – goldilocks Dec 12 '16 at 21:32
  • I readed that SM900 works on 3.2V to 4.8V, and RPi works on 5V, but the SM900 needs to 1A, just for him, that's what worries me. – Kross Dec 12 '16 at 23:06
  • Yeah that's probably pushing it -- although if you have no other devices, including USB, running, you might get away with it. Have a look at figure 2 here: raspberrypise.tumblr.com/post/144555785379/… ...Note the 5V rail will probably drop under that load, which may be a complication for your step down. I have a SIM800L in a drawer right now that's had me thinking about this; my plan is to power it independently, or try a clean, 3+ amp 5V source to cover both the pi and the step down. – goldilocks Dec 12 '16 at 23:22

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