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I am going to buy A6 GSM module for connecting to my Raspberry PI and making a little research here. Will I be able to power up this module purely from PI or external power source is a must?

A6 data specification says it requires from 4.9 to 9 volts. Can it be powered up, for example, from GPIO port, which seem to be provide 5V? Some sources say about 5V battery, but maybe it's just a a recommendation?

I am totally newbie in electronics and had no experience with PI before. I have Raspberry PI 2 model B revision 1.1.

UPDATE: I found out that module specified in my first link is not actually a SIM900 module so I corrected the title. It is A6 tagged as a replacement of SIM900 and seems to be based on GSM/GPRS A6 chip.

Also in the web I found several modifications tagged both as SIM900 and A6 (1, 2, 3), and all of them have different power consumption (1.3mA, 1.5mA, 2mA). As I have no particular preference in one GSM module over another during the purchase, opinions on any of them are appreciated. Real experience is highly appreciated.

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3 Answers 3

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It all depends on your power supply. The module seems to use about 1A (from the source you linked). If you are powering the Pi from a 2A microUSB connection as recommended, and you don't have any other peripherals (e.g. a Wi-Fi dongle), then yes, it is okay to power it from the 5V pin on the GPIO header. What another user posted about was the generic GPIO pins. These provide ~20 mA @ 3.3V, and can be switched by software. You would not use these, but the dedicated 5V port on the module.

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  • \$\begingroup\$ Thanks for the answer. Have you ever connected such modules to PI without external supply? Did you succeed? \$\endgroup\$
    – Suncatcher
    Apr 29, 2017 at 13:04
  • \$\begingroup\$ I have not. However, I have used devices with it that have similar power requirements (a Wi-Fi dongle) and an ESP8266. The module usually uses around 500mA, with peaks of 2A. Just to be safe, I would throw a capacitor that's at least 470 μF in parallel to it. \$\endgroup\$
    – lights0123
    Apr 29, 2017 at 13:25
  • \$\begingroup\$ Also, for people who say that it needs 3.2V to 4.8V, that is for the chip itself. The module contains a voltage regulator. What Pi are you using and how are you powering it? Do you have any extra peripherals? \$\endgroup\$
    – lights0123
    Apr 29, 2017 at 13:29
  • \$\begingroup\$ My Raspberry model is in question, and I power it from such adapter. I also have WiFi dongle but I do not plan to use them simultaneously. \$\endgroup\$
    – Suncatcher
    Apr 29, 2017 at 15:06
  • \$\begingroup\$ @Suncatcher your power supply does 2A, so you should be fine. Just make sure you disable/unplug the dongle. \$\endgroup\$
    – lights0123
    Apr 29, 2017 at 18:35
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Absolutely not, the maximum current draw for gpio pins is usually in the order of 10-20mA. You will need to use an external power supply for the module

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If you see reference design guide of Sim900 it clearly said

Normal operating voltage is from 3.2V to 4.8V. The peak working current can rise up to 2A during maximum power transmitting period, which will cause a voltage drop. So the power supply must be able to provide sufficient peak current, if not, the voltage may drop lower than 3.1V, and the module will automatically power down see 2.1 Power Supply Design

Now come to your question

SIM900 data specifications says it requires from 4.9 to 9 volts. Can it be powered up, for example, from GPIO port, which seem to be provide 5v?

Answer is no, Raspberry Pi GPIO pin allowed 16mA max current per pin & 2.3 VO with the total current from all pins not exceeding 51mA. See this datasheet

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  • \$\begingroup\$ BTW, how did you get the value of 51mA? \$\endgroup\$
    – Suncatcher
    Apr 29, 2017 at 13:02
  • \$\begingroup\$ If you load each pin with 16mA the total current is 272mA. The 3V3supply will collapse under that!. The raspberry-Pi 3V3 supply was designed with a maximum current of ~3mA per GPIO pin 3X17=51mA. You need to consider both conditions while using GPIO see this doc it describe well: scribd.com/doc/101830961/GPIO-Pads-Control2 \$\endgroup\$ Apr 29, 2017 at 13:36
  • \$\begingroup\$ Please click arrow if you got the answer. \$\endgroup\$ May 8, 2017 at 7:42

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