SIM900 GSM / GPRS Shield UART voltage levels

[burespe1]

Hello,

I would like to use SIM900 GSM / GPRS Shield with Raspberry Pi (RPi) and communicate over serial interface UART. Voltage level of UART on RPi 3.3 VDC.

Could I connect RPi directly to SIM900 GSM / GPRS Shield? (I found out that you support UART of SIM900 that has a 2.8 VDC logic and I guess that 5 VDC is implemented as well, may be also needed 3.3V?)
or do I have to use some voltage level converter? (like https://www.sparkfun.com/products/8745)

Thanks in advance

Petr

[techsupport]

Hi,friend
The SIM900 GSM / GPRS Shield is installed the voltage level converter,you can connect SIM900 GSM / GPRS Shield and Raspberry Pi (RPi) from serial interface UART directly .


Yours sincerely
techsupport

[justAq]

Can you please explain furthermore on how to connect between the two?

Raspberry Pi's UART Pins: TX/RX (3.3V) & GND Should be connected to....(SW Serial ? /HW Serial ? /UART (2.8) ? ) ?
How to configure the jumpers for using with Raspberry Pi?

[justAq]

Any response?

[treii28]

How do you get the uart to work? I tried connecting to the tx/rx/gnd using a 3.3v ftdi but couldn't seem to get a response out of an AT even with autobaud set. (I confirmed first the modem is working find with the arduino passthrough sketch)