4G LTE UART / USB Modem based on Quectel EC20 / EC25

 

Overview

 

The 4G LTE UART / USB  modem, a high quality commercial and industrial grade product from rhydoLABZ, which is professionally designed with impedance matching RF PCB designs and, is built with IoT/M2M-optimized Multi-Band LTE module from Quectel. This Modem based on QUECTEL module, will automatically fallback to  3G UMTS/HSPA+ and  2G mode in the absence of 4G Network , which will enable you to use it across the entire country including remote villages where 4G/3G towers are less populated . Since this modem supports GNSS ,customer can make use of Geo Location identification using  (GPS, GLONASS) Satellite networks.

Note: This EC20CE 4G UART modem is coming with VoLTE support , which will enable you to use JIO sim card on it.
Made in INDIA: The Modem is manufactured in fully automatic SMT production line at our own factory in INDIA. It is not a student grade low quality product or low cost china make products available in the market. It is designed and manufactured for industrial and commercial use .

 

 

What's On Board

 

  1. LDO Voltage Regulator IC
  2. GPS Voltage Regulator IC
  3. Main 4G LTE Antenna SMA Connector
  4. UFL Connector for Main 4G LTE Antenna
  5. UFL Connector for GPS Antenna
  6. N.Mode LED Indicator
  7. Status LED Indicator
  8. Net LED Indicator
  9. Power LED Indicator
  10. USB Micro B Connector for Communication
  11. Power Key (PKEY) Tactile Switch
  12. K4 RMC Power Connector
  13. K5 Serial Comm. RMC Connector
  14. K12 RMC Connector
  1. K10 RMC Connector
  2. K9 RMC Connector
  3. K14 RMC Connector (Serial Port Other Pins)
  4. Digital Audio CODEC interface 
  5. Jumper J10 for USB Boot mode selection
  6. 4G LTE Module
  7. UFL Connector for Diversity Antenna
  8. SMA Connector for Diversity Antenna
  9. Jumper J1 for Enabling GPS Power
  10. Micro SD Card Socket
  11. Micro SIM  Socket
  12. Jumper J3 for enabling automatic Power ON.
  13. Jumper J4 , for enabling Automatic Start on Powering.

 

 

Modem Basic Specifications

 

Communication Module QUECTEL EC20CEFILG-128-SGNS
Communication Network Supported 4G LTE, 3G , 2G, GPRS 
GNSS (GPS) Support Included (External Active Antenna included)
VoLTE Supported  Yes
Power Supply  5V – 13V DC
Current Requirement 300mA Normally (Peak up to 2Amp)
Modem Interfaces Serial UART , USB 
SIM Card Micro SIM (Sliding Type)
SD CARD Micro SD Card
Normal Operation Temperature -40°C ~85°C
Serial UART Baud rate Supported 4800bps  to 921600bps ( 115200bps is Default)

 

Outer Dimension of the Board

 

 

Connectors onboard

 

Connector Name Connector Details
K1 SMA Connector for GPS External Antenna (Active or Passive)
K2 UFL Connector for 4G LTE Main Antenna 
K3 Micro SIM Card Slot
K4 Power Supply Input
K5 USART Serial Communication Interface 
K6 USB Communication Interface
K7 Diversity/Auxiliary Antenna (Optional)
K8 Micro SD Card Slot
K9 Control & Status Interface
K10 Other I/O Pins, Debug Pins & ADC Pins for Advanced User
K11 PCM Digital Audio Pins for Connecting External CODEC if needed.
K12 Other MODEM O/P pins for Advanced User
K14 USART Communication Hardware Handshaking Pins for Advanced user 

 

 

 

Pin Functions

 

Connector PIN  Name I/O Functions
K4
K4 1 VCC Power Positive Power Input (5V-12V) DC Voltage
2 GND Power Negative Power Input (Ground)
K5
K5 1 V-INT Power Pin should be provided with required interfacing Voltage level. (Min 2.5V – Max 5V). Suppose user wants to interface modem with external 5V Microcontroller, then this pin should be supplied with 5V, incase of user want to interface with 3.3V Microcontroller , pin must be supplied with 3V3 , so on…
2 RXD D.Input USART Receive input PIN (Voltage level depends on V-INT Pin)
3 TXD D.Output USART Transmit output PIN (Voltage level depends on V-INT Pin)
4 GND Power Ground Return path for communication interface.
K9
K9
 
1 ON/OFF D.Input This PIN used to turn ON  or turn OFF modem power by Disabling EN pin of the internal Voltage Regulator IC. User can select either Automatic Mode or Manual mode powering option by Jumper J3. By default the PCB jumper J3 is Open and the Modem is in Automatic Powering mode. ie. once powered, Modem turned ON itself. If user wants to control the powering of the Modem manually , then the jumper should be Short and to turn ON the modem, user has to pull down  ON/OFF input. if unused, keep it Short.
2 PKEY D.Input Used to start and stop the modem by External microcontroller. Modem can start /stop automatically on powering or manually using this pin. A PCB jumper (J4) is provided to select this options. By default this jumper is shorted to start the Modem automatically on powering. User can remove the soldered jumper (J4) and control the modem using this pin.
In manual mode, Modem can be started by applying a HIGH level pulse having a width of more than 1 Second on this Pin and later can be stopped by applying again High level pulse having a width of more than 1 Second.if unused, keep it open.
3 RST D.Input Modem can be reset by applying HIGH level pulse having a width of minimum 500 milli second. if unused, keep it open.
4 F.MOD D.Input Flight Mode pin (W_DISABLE) is used to put the modem in to Airplane RF silence mode. Pull down this pin to enter Airplane mode. if unused, keep it open.
5 STS D.Output It is Modem status output. It is internally pulled up to V-INT voltage level using 10k Resistor. if unused, keep it open.
6 N.LIGHT D.Output It is GSM Modules NET-STATUS pin, voltage level inverted by a internal transistor. Indicate network activity status. Collector of this transistor is connected to internal LED (N-LED) and directly shared with this pin to connect external circuitry or LED through a current limiting resistor. if unused, keep it open.
K10
K10
 
1 ADC1 A.Input General purpose analog to digital converter input 1. If unused, keep it open. #1
2 DB-RX D.Input Receive debug data. If unused, keep it open. #1
3 ADC0 A.Input General purpose analog to digital converter input 0. If unused, keep it open. #1
4 DB-TX D.Output Transmit debug data. If unused, keep it open.#1
5 WUPIN D.Input WAKEUP_IN pin of the GSM module, for Sleep mode control. Cannot be pulled up before startup. Low level wakes up the module.  If unused, keep it open. #1
6 VBAT Power Out GSM Module VBAT pin is made out of this pin. Can be used for powering (3v3 – 4V) any other devices like Host microcontroller etc… If unused, keep it open.
7 APRDY D.Output AP_READY pin of the GSM module for application processor sleep state detection. If unused, keep it open.#1
8 GND Power Ground Return path for ADC interface. If unused, keep it open.
K11
K11
 
1 OUT D.Output PCM data output. If unused, keep it open. #1
2 SCL D.I/O PCM clock. If unused, keep it open. #1
3 IN D.Input PCM data input. If unused, keep it open.#1
4 SDA D.I/O I2C serial data. Used for external codec. If unused, keep it open.#1
5 SYNC D.I/O PCM data frame synchronization signal. If unused, keep it open. #1
6 GND Power If PCM Audio unused, keep it open.
7 CLK D.I/O I2C serial clock. Used for external codec.  If unused, keep it open.#1
8 GND Power If PCM Audio unused, keep it open.
K12
K12
 
1 DTR D.Input Data terminal ready, sleep mode control pin of the GSM Module , routed after voltage level conversion. Maximum input voltage HIGH level should be same as V-INT pin voltage. if unused, keep it open.
2 RI D.Output Ring indicator Pin of the GSM Module, routed after voltage level conversion. Maximum output voltage HIGH level will be same as V-INT pin voltage. if unused, keep it open.
3 N.MOD D.Output NET_MODE Indicate GSM module’s network registration mode, voltage level inverted by a internal transistor. Indicate network activity status. Collector of this transistor is connected to internal LED (N-LED) and directly shared with this pin to connect external circuitry or LED through a current limiting resistor. if unused, keep it open.
K14
K14
 
1 DCD D.Output DCD (Data carrier detection) pin of the GSM Module,routed after voltage level conversion.Maximum output voltage HIGH level will be same as V-INT pin voltage. if unused, keep it open.
2 CTS D.Output CTS (Clear to send ) pin of the GSM Module,routed after voltage level conversion.Maximum output voltage HIGH level will be same as V-INT pin voltage. if unused, keep it open.
3 RTS D.Input RTS (Request to send) pin of the GSM Module,routed after voltage level conversion.Maximum input voltage HIGH level should be same as V-INT pin voltage. if unused, keep it open.

 

#1: This pin is directly connected to the GSM Module, not used any voltage level conversion or current limiting in between and input/output voltage HIGH level is 1.8V. Care must be taken while using this pin to avoid damage to the GSM Module. If unused, keep it open

 

  • It is prohibited to supply any voltage to ADC pins when VCC or Modem Power is removed / Turned OFF.
  • It is recommended to use resistor divider circuit for ADC application.
  • It is recommended to use RESET only when failing to turn off the module by AT+QPOWD command or PKEY pin.
  • Ensure that there is no large capacitance on PKEY and RESET pins
  • ​In order to avoid damaging internal flash, please do not switch off the power supply when the module works normally. Only after the module is shut down by PWRKEY or AT command, the power supply can be cut off

 

 

Jumpers Onboard

 

Jumper  Type Default Function
J1 PCB Jumper Short Used to connect and disconnect 3V3 DC Voltage to GPS antenna connectors. For GPS active antenna this jumper should be shorted and for passive patch antenna it should be kept open.
J3 PCB Jumper Open Jumper 3 is used to select manual or automatic power controlling of the modem. By default it is open and in automatic mode ON Mode,which enable the modem to turn ON instantly upon applying the power to VCC pin. Even in this Automatic ON mode , you can control the Modem VBAT power by ON/OFF Pin on K9 connector. 

 

In order to turn ON/OFF modem manually by external microcontroller/circuit keep this jumper short. If the jumper is shorted , modem power will be OFF , until the your microcontroller boots ,starts your application  and pulling down the pin ON/OFF of K9 connector.

J4 PCB Jumper Short It is used to ground the PKEY pin of the EC20 module permanently, which wil enable automatic starting of the modem on powering. If user would like to control the modem by manually ,either by provided SMD Tactile switch SW1 or by host microcontroller via GPIO pin, this jumper should be kept open. 
J10 Hardware Jumper Open Used to put the gsm module in USB Boot mode.

 

 

Network Connection Status/Activity LED Indicator

 

Name Logic Level Changes Status
NMODE (NET_MODE) Always high Registered on LTE network
Always low Others
NLED (NET_STATUS) Flicker slowly (200ms high/1800ms low) Network searching
Flicker slowly (1800ms high/200ms low) Idle
Flicker quickly (125ms high/125ms low) Data transfer is ongoing
Always high Voice calling
PWR (Power ON LED) Always high Power LED will ON once the MODEM Power Turned ON.  
STS (Status)  Always high Once modem starts this LED will be ON
SW1 (PKey Switch)   Used to start / stop the modem manually. User has to press for more than 1 Second to start / stop the modem.

 

 

 

Getting  Started


 

Test the Modem out of box using MODEM USB port.
  1. Insert Micro SIM card to SIM card holder provided on bottom of the Board. Please ensure the direction of SIM Notch is same as the image shown nearby.
  2. Connect Provided LTE Antenna to the SMA Connector marked "MAIN" on the modem. #2
  3. Connect GPS Antenna to the connector marked K1.
  4. Install Required Quectel USB Driver software from the download link provided.(Device Manager view, before and after installations of USB Driver as below) 

    Before Installing Quectel USB Driver

    Device Manager AfterInstalling Driver

    After Installing Quectel USB Driver

  5. Connect Micro-B USB cable to the modem (K6) from Computer.
  6. Connect DC Power supply to the connector K1.(Ensure Polarity)
  7. When the modem is successfully powered-up, the PWR LED (Red) on the modem will be ON, the STS LED(GREEN) will light after 1-2 seconds, N.MODE LED (Yellow) will turn ON  and the NET LED(BLUE) will blink every second. After the Modem registers in the network (takes between 10-60 seconds), this LED will blink in step of 3 seconds.
  8. Open Serial Monitor Software and select respective COM Port (AT Port) and other settings on Computer as below. #3
    Default Setting are Baud rate :115200, Data bits:8 , Stop bit:1 and Parity:None
  9. ​AT<CR><LF>
    Now type and send simple attention command, "AT" followed by Carriage Return("/r") and New line ("/n") Character by expecting "OK" from the modem.
    Some of the Serial Monitor software will automatically append this Carriage Return/New line Character automatically or you have to add it asap.
    Once you got "OK" from the modem, all set and we can proceed with other commands…
  10. ATE0<CR><LF>
    To Turn OFF the Echo send by modem , we can issue "ATE0" followed by CR and LF.
  11. AT+CREG​?<CR><LF>
    Now we have to check whether the Modem is registered successfully with the SIM Provider Network by sending AT+CREG? followed by CR and LF. 
#2: Never use modem without connecting Main Antenna. This may damage the 4G Module.
#3: User can use any available Serial Port Software like DOCKLIGHT, REAL TERM, HYPER TERMINAL or QCOM from Quectel (included in the same downloaded Driver zip file)

 

 

Test the Modem using USB to Serial Converter board.
  1. Insert Micro SIM card to SIM card holder provided on bottom of the Board. Please ensure the direction of SIM Notch is same as the image shown nearby.
  2. Connect Provided LTE Antenna to the SMA Connector marked "MAIN" on the modem. #2
  3. Connect GPS Antenna to the connector marked K1.
  4. Connect UART Connector K5 to the USB to Serial Converter board using provided RMC Connector Cable as per below image.
  5. Connect the USB Converter to the Computer and Install the required USB Driver for the Converter board ( if not installed)
  6. Connect DC Power supply to the connector K1.(Ensure Polarity).
    You may be able to power the modem from USB to Serial Converter board's VCC Out pin also. But this entirely depends on the Computer's USB port capability.(Not guaranteed and Recommended)
  7. When the modem is successfully powered-up, the PWR LED (Red) on the modem will be ON, the STS LED(GREEN) will light after 1-2 seconds, N.MODE LED (Yellow) will turn ON  and the NET LED(BLUE) will blink every second. After the Modem registers in the network (takes between 10-60 seconds), this LED will blink in step of 3 seconds.
  8. Open Serial Monitor Software and select respective COM Port (AT Port) and other settings on Computer as below. #3
    Default Setting are Baud rate :115200, Data bits:8 , Stop bit:1 and Parity:None
  9. ​AT<CR><LF>
    Now type and send simple attention command, "AT" followed by Carriage Return("/r") and New line ("/n") Character by expecting "OK" from the modem.
    Some of the Serial Monitor software will automatically append this Carriage Return/New line Character automatically or you have to add it asap.
    Once you got "OK" from the modem, all set and we can proceed with other commands…
  10. AT+QURCCFG="URCPORT","UART1"<CR><LF>
    For redirecting the modem replies to the UART1 Port as well.
  11. ATE0<CR><LF>
    To Turn OFF the Echo send by modem , we can issue "ATE0" followed by CR and LF.
  12. AT+CREG​?<CR><LF>
    Now we have to check whether the Modem is registered successfully with the SIM Provider Network by sending AT+CREG? followed by CR and LF. 
#2: Never use modem without connecting Main Antenna. This may damage the 4G Module.
#3: User can use any available Serial Port Software like DOCKLIGHT, REAL TERM, HYPER TERMINAL or QCOM from Quectel (included in the same downloaded Driver zip file)

 

 

Test the Modem using Arduino UNO Board. (Basic/Simple 4 wire Connection)
  1. Insert Micro SIM card to SIM card holder provided on bottom of the Board. Please ensure the direction of SIM Notch is same as the image shown nearby.
  2. Connect Provided LTE Antenna to the SMA Connector marked "MAIN" on the modem. #1
  3. Connect GPS Antenna to the connector marked K1.
  4. Connect UART Connector K5 to the Arduino board using provided RMC Cable as per below image.
  5. Connect DC Power supply to the connector K1.(Ensure Polarity).
    You may be able to power the modem from ARDUINO Board VCC pin (5V-12V) also. But this entirely depends on your power supply/Arduino Board Voltage Regulator capability.(Not guaranteed by us)
  6. When the modem is successfully powered-up, the PWR LED (Red) on the modem will be ON, the STS LED(GREEN) will light after 1-2 seconds, N.MODE LED (Yellow) will turn ON  and the NET LED(BLUE) will blink every second. After the Modem registers in the network (takes between 10-60 seconds), this LED will blink in step of 3 seconds.
  7. Load the sample code provided to Arduino board and check the response on Arduino Serial Port Monitor window.
    Default Setting are Baud rate :115200, Data bits:8 , Stop bit:1 and Parity:None
  8. Once you got "OK" from the modem, all set and you can proceed with your required commands…
  9. ATE0<CR><LF>
    To Turn OFF the Echo send by modem , we can issue "ATE0" followed by CR and LF.

     

 

Test the Modem using Arduino UNO Board. (Advanced Mode)


Users those who wishes to control the modem Power, Start/Stop modem manually  or check the status of the modem periodically by hardware can opt the this advanced mode circuit connections as below .others can use above simple connection method.

  1. Remove the short on jumper J4 and keep it open.
  2. Ensure Jumper J3 shorted . 
  3. Insert Micro SIM card to SIM card holder provided on bottom of the Board. Please ensure the direction of SIM Notch is same as the image shown nearby.
  4. Connect Provided LTE Antenna to the SMA Connector marked "MAIN" on the modem. #1
  5. Connect GPS Antenna to the connector marked K1.
  6. Connect UART Connector K5 to the Arduino board using provided RMC Cable as per below image.
  7. Connect DC Power supply to the connector K1.(Ensure Polarity).
    You may be able to power the modem from ARDUINO Board VCC pin (5V-12V) also. But this entirely depends on your power supply/Arduino Board Voltage Regulator capability.(Not guaranteed by us)
  8. When the modem is successfully powered-up, the PWR LED (Red) on the modem will be ON, the STS LED(GREEN) will light after 1-2 seconds, N.MODE LED (Yellow) will turn ON  and the NET LED(BLUE) will blink every second. After the Modem registers in the network (takes between 10-60 seconds), this LED will blink in step of 3 seconds.
  9. Load the sample code provided to Arduino board and check the response on Arduino Serial Port Monitor window.
    Default Setting are Baud rate :115200, Data bits:8 , Stop bit:1 and Parity:None
  10. Once you got "OK" from the modem, all set and you can proceed with your required commands…
  11. ATE0<CR><LF>
    To Turn OFF the Echo send by modem , we can issue "ATE0" followed by CR and LF.

     

 

 

Examples


 

Sending SMS using USB From Computer 
  1. Connect Modem to Computer using either on board USB Port or using External USB to Serial converter board.
  2. Open Serial port software and enter the below command to send SMS.

    • AT<CR><LF> 
      Attention Command,  this signifies that our Modem is working properly. 
      Answer Expected : OK

    • ATE0<CR><LF> 
      This Command is being sent to stop the echo.
      Answer Expected : OK

    • AT+CREG?<CR><LF> 
      It is being used to check whether the SIM got registered with the Network.
      Answer Expected : +CREG: 0,1  or +CREG: 0,5

    • AT+CMGF=1<CR><LF> 
      Configuring Text mode for sending SMS
      Answer Expected : OK

    • AT+CMGS="Mobile Number"<CR><LF> 
      Set the destination mobile number enclosed in the DOUBLE QUOTES.
      Answer Expected : >

    • "Hi, How are you?"<SUB>
      Here we enter our message body followed by CONTROL-Z (<SUB>) 
      Answer Expected : SMS confirmation starting with "+CMGS"

  3. SerialMonitor Software Command/Response View for Sending SMS.
    SerialMonitor Software Command/Response View for Sending SMS.

 

Sending SMS using ARDUINO via UART 
  • Arduino Code using Software Serial port download 

     

  • Since Arduino UNO is sharing its serial port with USB IC via 1K Ohm series resistor , you may face difficulty to use normal serial port along with this modem. So above arduino codes are based on  Software serial interface . 
  • Arduino PIN 2 and PIN3 are used as RX and TX respectively for interfacing with Modem TX and RX.
     
Reading SMS using Quectel EC20/EC25 4G LTE Modem 
  • AT<CR><LF> 
    Attention Command,  this signifies that our Modem is working properly. 
    Answer Expected : OK
  • ATE0<CR><LF> 
    This Command is being sent to stop the echo.
    Answer Expected : OK
  • AT+CREG?<CR><LF> 
    It is being used to check whether the SIM got registered with the Network.
    Answer Expected : +CREG: 0,1  or +CREG: 0,5
  • AT+CMGF=1<CR><LF> 
    Configuring Text mode for SMS
    Answer Expected : OK
  • AT+QURCCFG="URCPORT","UART1"<CR><LF>
    For redirecting the modem replies to the UART1 Port as well.
  • AT+CNMI=2,1,0,0,0<CR><LF>
    Configure Modem to notify on incoming SMS reciept. Modem will inform the SMS reciept by "+CMTI:<Message index Number> "
  • AT+CMGR=<Message index Number>
    Now Read SMS using <Message index Number> received.

 

 

How to get GPS Location using Quectel EC20/EC25 4G LTE Modem
  • AT<CR><LF> 
    Attention Command,  this signifies that our Modem is working properly. 
    Answer Expected : OK
  • ATE0<CR><LF> 
    This Command is being sent to stop the echo.
    Answer Expected : OK
  • AT+QGPS=1<CR><LF> 
    Turn ON the GPS Function .
    Answer Expected : OK
  • AT+QGPSLOC?<CR><LF> 
    Initially we have to wait atleast 30 Seconds and issue this command to read the GPS location details
    Answer Expected : GPS Data starting  with "+QGPSLOC:"
  • AT+QGPSEND<CR><LF> 
    Turn OFF the GPS Function before exiting.
    Answer Expected : OK

 

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