3G SARA click

Fully functional 3G transceiver

To start using 3G SARA click you will need a SIM card and an SMA antenna (sold separately), plus a mic/earphone headset if you want to send and receive calls. Everything else is already on the board.

Apart from the SIM card slot, SMA antenna connector, audio jack and audio codec IC, 3G SARA click also has a Micro USB port to connect the module to a PC.

u-blox provides a free PC app for sending and receiving messages and calls from your computer. Developers can also write their own custom applications using the USB-UART communication line.

The mikroBUS™ UART pins are used to connect the module to a target board MCU. Separate pins provide network status reporting and incoming call detection.

SARA’s award-winning flexibility

M2M Evolution Magazine named SARA-U2 modules “Product of the Year” in 2014. Several standout features make it desirable for professional developers.

All SARA modules share the same form factor. You can replace one SARA module with another on the same PCB design and preserve almost all the functionality – allowing you to design hardware that is easy to adjust and upgrade.

This makes 3G SARA click a great prototyping tool, whether you are designing consumer electronics or adding M2M communications to industrial devices.

Read more about the module in the vendor’s data sheet.

What makes 3G so convenient?

3G modems allow you to take advantage of the vast cellular network infrastructure that spans the entire globe. It's the most convenient solution for long-range wireless data transmission — especially with the increased bandwidth that 3G provides compared to 2G GSM.

3G is short for third generation. The U201 module is specified as 3.75G, which simply means it is compatible with HSPA+ (in addition to previous generation UMTS, GPRS and EDGE networks)

If you are not familiar with cellular network standards and protocols and are not sure whether you need GSM or 3G, read our learn.mikroe.com article about 2G/3G/4G to get a better understanding.

Another article, about AT commands and parsers will also help you understand how to program GSM/3G modems in general.

Applications

• Mobile internet terminals
• Automatic meter reading
• Remote monitoring and control
• Surveillance and security
• Point of Sales terminals in retail
• Smartphone-enabled automation (garage door opener, A/C activator, electric door lock control and so on)

Specifications

Pinout diagram

This table shows how the pinout on 3G SARA click corresponds to the pinout on the mikroBUS™ socket (the latter shown in the two middle columns).

Notes	Pin					Pin	Notes
Network Status	STAT	1	AN	PWM	16	RI	Incoming ring detection
Power ON/OFF	PWRKEY	2	RST	INT	15	CTS	UART Clear To Send
UART Request to Send	RTS	3	CS	TX	14	TXD	UART Data Transmit
	NC	4	SCK	RX	13	RXD	UART Data Receive
	NC	5	MISO	SCL	12	NC
	NC	6	MOSI	SDA	11	NC
Power supply	+3.3V	7	3.3V	5V	10	+5V	Power supply
Ground	GND	8	GND	GND	9	GND	Ground

STAT pin (#1) shows the network status. The pin configured to provide the “Network status indication” function is set as:

• Continuous Low: if no service (no network coverage or not registered)
• Cyclically High for 100 ms, Low for 2 s: if registered home 2G network
• Cyclically High for 50 ms, Low for 50 ms, High for 50 ms, Low for 2 s: if registered home 3G network
• Cyclically High for 100 ms, Low for 100 ms, High for 100 ms, Low for 2 s: if registered visitor 2G network (roaming)
• Cyclically High for 50 ms, Low for 50 ms, High for 50 ms, Low for 100 ms: if registered visitor 3G network (roaming)
• Continuous High: if voice or data 2G/3G call enabled

3G SARA click can run on either a 3.3V or a 5V power supply. 3.3V is selected by default. To switch to 5V, use the onboard jumpers (zero ohm resistors).

Programming

Code examples for 3G SARA click, written for MikroElektronika hardware and compilers are available on Libstock.

The code example we provide requires you to provide PIN definitions inside your project, to match the mikroBUS™ socket where the click is placed. You will also need to edit the interrupt routine inside “dev_hal.c” file if needed – depending on the UART BUS used.

The idea of the demo is to make a remote lock for a gate which locks on unlocks the gate using relay click by calling the phone number which is inserted to 3G Sara click board. Only phone numbers stored in “approved” variable inside the “3G_sara_gate.c” file can toggle the relay. User can also edit “platoform.pld” file to have everything logged on UART bus for debug.

Code snippet

This routine checks caller ID and compares it to the numbers stored in “approved” variable. If the same number exists this function toggles the relay and sends confirmation message about the relay state.

 1 void reply_info_to_caller( void )
2 {
3   int check;
4   char tmp_cmd[ 50 ] = { 0 };
5
6   for( check = 0; check < SUBSCRIBERS; check++ ){       // Check caller ID
7     if( !strcmp( tmp_num, approved[check] ) ){
8
9       strcpy( tmp_cmd, "AT+CMGS=" );                    // Compose sting for new SMS with caller ID
10       strcat( tmp_cmd, tmp_num );
11       at_cmd( tmp_cmd );
12
13       if( !RELAY_1 )
14         at_cmd_addition( "Access granted!" );
15       else
16         at_cmd_addition( "Gate locked!" );
17
18       RELAY_1 = ~RELAY_1;                               // Toggle relay
19     }
20   }
21 }