GSM 4 Click Board™

Product Code: MIKROE-2388

The GSM 4 Click Board™ is a compact quad-band GSM cellular network communication solution, featuring the quad-band 2.5G GSM/GPRS SARA-G350 module. This module features a full set of options for the cellular networking and communication, such as the network status indication, jamming detection, embedded internet protocols, including TCP/IP, UDP, FTP, PPP, HTTP, SMTP, full GPRS multislot class 10 implementation, and more. Data communication speed is rated up to 42.8 for the uplink and 85.6 kbps for downlink connection. This module offers high quality integrated audio interface, allowing voice communication over the onboard 3.5mm headset connector, and the USB connector. The GSM 4 Click Board™ supports quad-band GSM/GPRS, allowing it to be used worldwide. A wide range of communication protocols and connectivity options, packed in the compact size module, driven by the simple AT command interface via the UART bus, make this click board™ a complete solution for a wide range of M2M applications, such as mobile Internet terminals, automatic meter reading (AMR), remote monitoring automation and control (RMAC), surveillance and security, road pricing, asset tracking, wireless points of service (POS) and similar applications, which rely on a cellular network connection.

How Does The GSM 4 Click Board™ Work? The GSM 4 Click Board™ is equipped with the SARA-G350, a compact, quad-band 2.5G GSM/GPRS module, from u-blox. It covers frequencies of 850/900 MHz and frequencies of 1800/1900 MHz. It is class 10 compliant, featuring 4 download slots / 2 upload slots, supporting 5 slots in total. This module is the main component of the click board and it consists of a number of internal blocks or sections, such as antenna switching section, RF transceiver section, memory, power management, and most importantly - the cellular baseband processor. The module interface consists of several lines used to report the device and the network status, SIM card interface lines, UART interface lines, and device control lines. These lines are routed to the respective elements of the click board. The SARA-G350 module has to be powered by a clean and stable power supply. The voltage needed for the module to work properly is about 4V and it is derived from the 5V mikroBUS™ rail, through the MCP1826, a 1A low drop output (LDO) regulator from Microchip. Although the SARA-G350 is a low power device, the cellular network modules in general, are notorious for their high power consumption, so the 1A LDO had to be used. Digital sections of the SARA-G350 are internally supplied by 1.8V, so it is necessary to condition the communication bus lines which connect the host MCU with the module. SARA-G350 outputs 1.8V output from its internal LDO, providing a needed reference voltage for one side of the TXB0106, a 6bit bidirectional level shifting and voltage translator with automatic direction sensing, from Texas Instruments. The reference voltage for the other side of the level shifter is taken from the onboard SMD jumper, labelled as I/O Level This jumper is used to select between 3.3V and 5V from the mikroBUS™, depending on the used MCU type and its logic voltage level requirements. UART interface supports baud rates from 2400 bps to 115.2 kbps and automatic baud rate detection for up to 115.2 kbps. The automatic baud rate detection mode is set by default. The UART bus of the SARA-G350 module is connected to one side of the level shifter, while the other side (shifted) is connected to the respective mikroBUS™ UART pins (TX and RX). However, the SARA-G350 module is designed as the traditional DCE device (Data Communication Equipment) offering the full UART pin count, including the hardware flow control pins (CTS, RTS). These pins are routed to the mikroBUS™ CS (RTS) and the INT pin (CTS) and are used if the hardware flow control is enabled. The RI pin is the Ring Indicator, and it is routed to the mikroBUS™ PWM pin. GSM 4 click offers USB interface via the micro USB connector, routed to the dedicated USB to UART IC. The FT230X IC is used for this purpose, a well-established USB to UART solution from FTDI Company, used on many MikroElektronika products. Besides to the level shifter IC, the same UART lines from the SARA-G350 are also routed to this USB to UART IC, offering an easy access to the SARA-G350 module via the personal computer and USB connection. The GSM 4 Click Board™ is populated with two pairs of LED indicators, which are used to provide a visual feedback of the Click board™ communication status. One pair of LEDs belongs to the USB section and the USB to UART IC, while the second pair of LED indicators belongs to the SARA-G350 module itself. In addition, one pair of LEDs is labelled with USB, while the second pair of LEDs is labelled with GSM. This makes it easy to understand which LEDs are used for the specific function. GSM LEDs: These LEDs are routed to the GPIO1 and GPIO2 pins of the SARA-G350 module. GPIO 1 pin is routed to a red LED