This document shows the documentation for the rhomb GPS/GPRS SIM868 Module.


The GPS/GPRS SIM868 Module is a certified rhomb module that allows GNSS possitionining and GPRS low speed communication. Even more, it has an optional Bluetooth communication interface.

The GNSS part has a low power consumption performance (22~24 mA) and supports various location applications including GPS, GLONASS, BEIDOU, QZSS, SBAS (WAAS, EGNOS, GAGAN, and MSAS) and A-GPS.

The GPRS part, it is quad-band 850/900/1800/1900MHz GSM/GPRS, with maximun speed of 85.6 kbps, available in eSIM and MicroSIM versions.

And about the optional part, it is Bluetooth 3.0 compliant (firmware upgrade required).

All three parts has a 50Ω UMCC antenna conector for each one.

The next figure show a 3D view for the GPS/GPRS SIM868 Module.

GPS-GPRS Module based on SIM868 TOP.png GPS-GPRS Module based on SIM868 BOTTOM.png


  • Tracking
  • Telemetry
  • Remote location
  • Remote control

Module specification

This module has been build around the SIM868 chipset from SIMCOM Technology that integrates GNSS location, GSM/GPRS and Bluetooth 3.0. It can be controlled using the two UART connections or through a high-speed USB interface thanks to the integrated USB controller CP2105. All three parts can be controlled using AT commands in Main UART interface, although it is recommended to use the secondary interface for GPS data because of the amount of frames required.

The following figure identifies the main Integrated Circuits (IC) onboard.

GPS-GPRS Module based on SIM868 TOP Indicaciones.jpg GPS-GPRS Module based on SIM868 BOTTOM Indicaciones.jpg

The next figure shows the Block Diagram for the SIM868 Module.

GPS-GPRS Module based on SIM868 Diagram.png

GPS part features
Channels 33 tracking / 99 acquisition
Time to First Fix (Cold starts) 28 s
(Warm starts) 26 s
(Hot starts) < 1 s
Accuracy Horizontal position: < 2.5 m CEP
Speed: 0.1 m/s
GPRS part features
Frequency: 860/900/1800/1900 MHz
GPRS class 12: 85.6 kbps (downlink/uplink)
Coding schemes: CS 1, 2, 3, 4
Enlace PPP-stack

User interfaces

There are some Solder Jumpers (smd 0402 compatible) to select some functionality:

1 - GPS can be powered using line BUCK8 (3V3) or the main power supply (VSYS & VBAT).

2 - GPS/GPRS module has different communication possibilities:

  • GSM UART <--> UART1 rhomb || USB UART1
  • GPS UART <--> UART3 rhomb || USB UART2 || AT commands on GSM UART.

3- USB controller (CP2105) power supply. It can be disconnected if not used.

If we are using a powerfull rhomb core you can use USB interface for GPRS & GPS communication. If we are using a uC with more than one UART (Duino Mega, for example, that is based on Arduino Mega), we can use both chipset UARTs, GSM & GPS. If we are using a uC with just one UART (Duino UNO) we have to use AT commands on GSM UART to control GPS. In this case, GPS UART should be connected to an auxiliary UART in SIM868 chipset.



The following table summarizes the GPIOs used on the GPS/GPRS module. Note that ZZ of them should be configured as interrupt sources.

rhomb pinout Signal (module) Device Interruption
GPIO0 GSM.PWR_EN Power Switch No
GPIO2 GPS.EN Main IC (SIM868) No
GPIO4 GSM.RI Main IC (SIM868) Yes/No
GPIO5 GPS.1PPS Main IC (SIM868) Yes/No

For more details, look at the module specifications for the rhomb standard.

Serial interfaces

The following table indicates the available serial interfaces on the rhomb standard and its been indicated the used ones. The table also shows the nomenclature used on the rhomb standard and its corresponding on the schematic.

Signal (rhomb) Signal (module) Used by Signal (rhomb) Signal (module) Used by
I2C_SDA Unused SPI_MISO Unused
I2C_SCL Unused SPI_MOSI Unused
I2C_INT Unused SPI_CLK Unused
Main UART SPI_CSn Unused
Secondary UART
UART3_RXD Secondary UART RX SIM868
UART3_TXD Secondary UART TX SIM868

As it has been explained in the "Module specifications" section, GPS/GPRS module can be controlled trough UART or USB. For more details, look at the module specifications for the rhomb standard.


The Secure Digital Input Output (SDIO) interfaces are not used on the GPS/GPRS SIM868.


As per the supply lines used on the board, there is a summary on the next table.

Signal (rhomb) Signal (module) Voltage (V) Used
1V8 150mA 1.8 No
2V8 150mA 2.8 No
VBAT 5 Yes
VSYS 3 - 5.5 Yes
Buck8 3.3 Yes
Buck9 3.3 No

For more details, look at the module specifications for the rhomb standard.

Other signals

The CLK_32KH, AD_OUT and PWM_INT signals are not used on the GPS/GPRS. More information regarding these signals can be found at the specifications for the rhomb standard.

For more details, look at the module specifications for the rhomb standard.


Click the image below to download the schematic files.

Bill of materials

The BOM for different versions are here:

SIM868 (SIM Holder)

SIM868 (eSIM)

Fabrication files

Click the image below to download the fabrication files.

Mechanical specifications


Expansion Dimensions v2.JPG


  • Precaution against Electrostatic Discharge. When handling products, ensure that the environment is protected against static electricity. Follow the next recommendations:
  1. The users should wear anti-static clothing and use earth band when manipulating the device.
  2. All objects that come in direct contact with devices should be made of materials that do not produce static electricity that would cause damage.
  3. Equipment and work table must be earthed.
  4. Ionizer is recommended to remove electron charge.
  • Contamination. Be sure to use semiconductor products in the environment that may not be exposed to dust or dirt adhesion.
  • Temperature/Humidity. Semiconductor devices are sensitive to environment temperature and humidity. High temperature or humidity may deteriorate semiconductor devices characteristics. Therefore avoid storage or usage in such conditions.
  • Mechanical Shock. Care should be exercised not to apply excessive mechanical shock or force on the connectors and semiconductors devices.
  • Chemical. Do not expose semiconductor device to chemical because reaction to chemical may cause deterioration of device characteristics.
  • Light Protection. In case of non-EMC (Epoxy Molding Compound) package, do not expose semiconductor IC to strong light. It may cause devices malfunction. Some special products which utilize the light or have security function are excepted from this specification.
  • Radioactive, Cosmic and X-ray. Semiconductor devices can be influenced by radioactive, cosmic ray or X-ray. Radioactive, cosmic and X-ray may cause soft error during device operation. Therefore semiconductor devices must be shielded under environment that may be exposed to radioactive, cosmic ray or X-ray.
  • EMS (Electromagnetic Susceptibility). Note that semiconductor devices characteristics may be affected by strong electromagnetic waves or magnetic field during operation.

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