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4G, 3G, 2G GSM shields frequent ask question (FAQ) section

4G, 3G, 2G GSM shields FAQ :: UART INTERFACING AVOID COMMON ERRORS



Serial [UART] wiring info related

UART signals for 4G, 3G, 2G GSM shields

Step 1:
All itbrainpower.net modular modem shield type (c-uGSM, h-nanoGSM, d-u3G or l-LTE) share the same ITBP interface. First of all, identify on your itbrainpower.net modular modem following signal pads:
- RX(TXD) - named bellow MDM-TXD
- TX(RXD) - named bellow MDM-RXD
and
- GND - named bellow MDM-GND

Right image - c-uGSM shield.

 

Step 2:
Identify on your micro-controller (or, let's say USB UART adapter, if you connect it with third USB UART adapter) the following pins:
- TX - named bellow uCTRL-TX
- RX - named bellow uCTRL-RX
and
- GND - named bellow uCTRL-GND

 

Step 3:
Cable the wire as described bellow:
- MDM-TXD goes to uCTRL-RX
- MDM-RXD goes to uCTRL-TX
and
- MDM-GND goes to uCTRL-GND

DONE!

 

Serial [UART] supported interfacing voltages. It is Arduino 3.3V only shields direct interfacing possible?

UART and other CONTROL [POWER and RESET] and STATUS signals on itbrainpower modems supports:
- a-gsm, a-gsmII, b-gsmgnss, c-uGSM and h-nanoGSM - 2.8V up to 5V, auto select
- d-u3G and l-LTE - 3.3V up to 5V, auto select

YES, interfacing of any itbrainpower.net modems [full-size or modular] with 3.3V only Arduino shields [same as Teensy or Raspberry PI or Beagle Bone Black boards, others..] can be made WITHOUT need for level convertor boards.

 

Serial [UART] speed info related. Choose the proper UART speed.

Our full size modems are shipped with following default speeds [in brackets, supported speeds]:
- a-gsm - autobaud, 8N1 [4800, 9600, 19200, 38400, 57600 and 115200]
- a-gsmII - autobaud, 8N1 [4800, 9600, 19200, 38400, 57600 and 115200]
- b-gsmgnss - autobaud, 8N1 [4800, 9600, 19200, 38400, 57600 and 115200]

Our modular modems are shipped with following default speeds [in brackets, supported speeds]:
- c-uGSM - autobaud, 8N1 [4800, 9600, 19200, 38400, 57600 and 115200]
- h-nanoGSM - autobaud, 8N1 [4800, 9600, 19200, 38400, 57600 and 115200]
- d-u3G - autobaud, 8N1 [4800, 9600, 19200, 38400, 57600 and 115200 + 230400, 460800, 921600]
- l-LTE - 115200bps, 8N1 [4800, 9600, 19200, 38400, 57600, 115200, 230400, 460800, 921600 and 3000000bps]

Recommended speed for Arduino (and other slow ucontrollers) / RPI, BBB or fast ucontrollers / PPP:
- a-gsm, a-gsmII, b-gsmgnss, c-uGSM and h-nanoGSM - 9600 bps, 19200 bps / 115200 bps
- d-u3G - 9600 bps, 19200 bps / 921600 bps
- l-LTE - 9600 bps, 19200 bps / 921600 bps

 

Settings in Arduino demo software related to serial [UART].

Check for "usejLader" define in our published Arduino demo software .

If you connect your modular modem using "j-328GSM3GLader - Arduino Micro / Arduino Mini / Arduino Nano adapter board" be sure the: #define usejLader
compiling directive it is NOT COMMENTED.
If you do not use "j-328GSM3GLader adapter" make sure the:
#define usejLader
compiling it is COMMENTED.

 

 

 

 

this tutorial was written by Dragos Iosub.

 

document version 0.9 / 2018-02-12 © R&D Software Solutions srl