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MOTG-BLUETOOTH provides low-cost and low-energy solutions for all embedded Bluetooth applications. The MOTG-BLUETOOTH carries an RN4870 Bluetooth module, providing a complete solution to implement Bluetooth 4.2 Low energy connectivity.

The MOTG-BLUETOOTH can be dynamically configured easily using ASCII commands using the host microcontroller.


  • RN4870 Bluetooth Module by Microchip with
  • Bluetooth 4.2 Low Energy Stack
  • ASCII Command Interface API over UART
  • Secure AES128 Encryption
  • 3.3V Power supply only
  • Supports 2-Wire 3.3V TTL UART Interface
  • Integrated Ceramic Chip Antenna
  • On-board Status LED
  • Remote configuration Over The Air
  • ISM Band 2.402 GHz to 2.480 GHz Operation
  • Channels: 0-39
  • Receive Sensitivity: -90 dBm (LE)
  • Transmit Power: 0dBm

Before Getting Started

Out of the box, the chipset's UART pins are not connected to the UMI of the MOTG.

MOTG-BLUETOOTH hardware allows the UART pins to be connected to either TX, RX or GPIO1, GPIO2 of the UMI. This is could be achieved by shorting the respective sides of solder bridges SB2 and SB3 using a solder blob and soldering iron. This must be completed by the User.


Unless the designer intends to use two UART MOTGs on a gen4-MOTG-AC2 or gen4-MOTG-AC4 board, the UART pins should be directed to TX, RX of the UMI as shown above.

When two UART MOTGs are being used on a gen4-MOTG-AC2 or gen4-MOTG-AC4 board, the UART pins of one of the MOTGs should be diverted to GPIO1 and GPIO2 of the UMI, as shown below. This prevents both MOTGs from using the same pins of the gen4 display module for UART communication.


Chipset Features

RN4870 Bluetooth Module

The RN4870 module, based on Microchip's IS187x Bluetooth LE ICs, is a leading platform for Bluetooth-related projects or the Internet of Things (IoT).

RN4870 Bluetooth Module

This Bluetooth Low Energy module incorporates Bluetooth 4.2 baseband controller, on-board Bluetooth stack and RF power amplifier.

The data sheet for the RN4870 is available from the Microchip website. In addition, more support has been made available for this module by Microchip.

Pins and Solder Bridges

Pin Description

Pin Description

Pin Symbol Description
1 3.3V 3.3V Input Supply
2 GND Supply Ground
3 RX Asynchronous Serial Receive Pin
4 TX Asynchronous Serial Transmit Pin
5 N/C Not Connected
6 GPIO4 P2_0/MODE Pin
7 GPIO3 Reset pin. An active Low pulse will reset the module
8 GPIO2 RX Bypass Pin
9 GPIO1 TX Bypass Pin
10 N/C Not Connected
11 N/C Not Connected
12 N/C Not Connected
13 N/C Not Connected
14 N/C Not Connected
15 GND Supply Ground
16 N/C Not Connected


The designer can choose if the UART pins of the MOTG should be connected to either TX, RX or GPIO1, GPIO2 of the UMI. This could be achieved by shorting the respective sides of solder bridges SB2 and SB3. This is discussed in detail in Before Getting Started.

Solder Bridge Description

The MOTG-BLUETOOTH has three solder bridges. The functionality of those solder bridges is described in the table below. These are soldered by the User.

Solder Bridge Description

Solder Bridge Description
SB1 Short to use the GPIO4 to change/upgrade firmware
SB2 TX selector
SB3 RX selector

Firmware Programming

The MOTG-BLUETOOTH comes pre-programmed with firmware version 1.18.3. If an updated command set is desired instead, then the default firmware will be lost. The following procedure outlines how to reload the RN4870 with the default firmware. Below are the six pins of the MOTG-BLUETOOTH that will be used when uploading firmware.

  • +3.3V (not 5V tolerant)
  • GND
  • RX
  • TX
  • GPIO3 (Reset)
  • GPIO4 (P2_0/MODE)

Firmware Programming

In this case, a gen4-MOTG-AC1 is used to gain access to the essential pins of the MOTG-BLUETOOTH. However, other gen4-MOTG-AC interface boards provided by 4D Systems could be used as well. The gen4-MOTG-AC1 is then interfaced with the gen4-PA, which essentially serves as a breakout board for the UMI pins in this setup.


If you opt to use MOTG-BREADTOOTH instead of the gen4-MOTG-AC1 + gen4-PA combo, the 5V needs to be dropped to 3.3V externally, as MOTG-BREADTOOTH does not facilitate this internally.

Lastly, a programming module is needed to program the MOTG-WiFi-ESP through the gen4-MOTG-AC1 + gen4-PA combo. This process does not necessarily require a 4D Systems programming module - the 4D USB programming cable or the uUSB-PA5. However, these are compatible and could be used to perform this procedure.

Carefully, slide the MOTG-BLUETOOTH on the gen4-MOTG-AC1 board. Connect the 4D programming module to the corresponding pins of the gen4 PA as shown in the image below.


The RN4870 needs to be placed into Test mode. The following procedure will place the Bluetooth module in Test mode.

  • Connect GPIO 9 (P2_0/MODE Pin) of the gen4 PA to the Ground.

Connect GPIO 9

  • While GPIO 9 of the gen4 PA is grounded, connect the GPIO10 (Reset) pin to Ground for a second and disconnect it (Reset) from Ground.


  • Now disconnect GPIO 9 as well from Ground.

Disconnect GPIO 9

Please download the RN4870 firmware files from the MOTG-BLUETOOTH product page on the 4D Systems website. Extract the files to a known location on your hard drive that is easy to access.

Run the ISupdate Programming Utility and set the baud rate to 115200 and the memory type to Flash/Embedded**. Then check the com port of the 4D programming module and change it accordingly in the application.

Com port

Click Connect. If the connection was successful, the application will confirm by printing the following message.


Click the Browse button and navigate to the folder where the firmware package was extracted to. Select all hex files and click Open.


Click Update. Allow a few seconds for the update to complete.


Now you can disconnect and close the ISupdate tool.


The version of the firmware can be verified by opening a CoolTerm connection.

CoolTerm Connection

Ensure the details are correct as per the picture, and set to the following:

  • Baudrate: 115200
  • Data Bits: 8
  • Parity: None
  • Stop Bits: 1
  • Flow Control: None

In addition, the Local Echo has been turned on in the Terminal tab.

Now, enter the Command Mode and Verify Version using the following steps.

  • Press $ to enter Command Mode
  • Press V to display the firmware version.

Command Mode

The above confirms that the Bluetooth module has been updated to version 1.18.3 of the firmware.

Mechanical Views

Mechanical Views

Schematic Details

Schematic Details


Recommended Operating Conditions

Parameter Conditions Min Typ Max Units
Supply Voltage (VCC) Relative to VSS 1.9 3.3 3.6 V
Operating Temperature -20.0 -- 70.0 °C
Storage Temperature -65.0 -- 150.0 °C
Input Low Voltage (VIL) All pins VSS -- 0.3*VCC V
Input High Voltage (VIH) All pins 0.7*VCC -- VCC V

Global Characteristics Based on Operating Conditions

Parameter Conditions Min Typ Max Units
Peak Current TX mode, VCC = 3V, TX = 0 dBm, Buck mode -- -- 13.0 mA
RX mode, VCC = 3V, Buck mode -- -- 13.0 mA
Standby Current 1.9 -- 2.9 uA
Output Low Voltage (VOL) VSS -- 0.2*VCC V
Output High Voltage (VOH) 0.8*VCC -- VCC V

Revision History

Hardware Revision

Revision Number Date Description
1.1 23/09/2016 Initial Public Release version

Datasheet Revision

Revision Number Date Description
1.8 06/01/2023 Modified datasheet for web-based documentation