DMR818S and External MCU Connection Instructions

Before discussing how to successfully connect the DMR818S radio module with an external MCU (Microcontroller Unit), let's briefly understand these two products.

The DMR818S is a powerful radio module that supports both digital and analog communication. It features long-distance transmission, high reception sensitivity, and SMS functionality, making it ideal for scenarios requiring efficient communication. The MCU, as the core of an embedded system, is responsible for control, data processing, and interaction with external devices.

To understand the connection between the DMR818S and an external MCU, it is essential to carefully review the DMR818S datasheet and circuit diagram to determine the function of each pin. Typically, a radio module includes power pins, communication pins, control pins, and an antenna interface.

The specific process for connecting the DMR818S with an external MCU is as follows:

1.Pin Definition and Matching
Based on your MCU model and datasheet, identify the corresponding pins. Ensure that the power pins, communication pins, and control pins are correctly aligned. The DMR818S module pin diagram is as follows:

2.Power Connection
DMR818S and MCU Connection Diagram

Taking the connection between the DMR818S and the U1 R8C1A (MCU) as an example, first, power the DMR818S module with an external 4.2V power supply (pins 8, 9, and 10 connected to ground). Then, connect the module's voltage output pin to the MCU's power pin.

Pay close attention to the MCU's voltage requirements, as the external power supply of the module may exceed the MCU's operating voltage. The module needs to provide a stable VDD voltage that matches the MCU's operating voltage. According to the pin definition table and the MCU connection diagram, pin 15 of the DMR818S module can output a stable 3.3V voltage, which matches the MCU's 3.3V operating voltage. Therefore, pin 15 (voltage output) of the DMR818S module should be connected to pin 7 (VCC) of the MCU, allowing the MCU to obtain the required VDD voltage from the module's stable output.

Additionally, the module's ground (GND) pin must be connected to the MCU's ground pin. This ensures the two share the same electrical potential, forming a complete power circuit.

3.Communication Interface Connection
The DMR818S supports a UART communication interface. Choose the appropriate communication interface based on the MCU and application requirements. When connecting to the U1 R8C1A, connect pin 2 (UART-TX) and pin 3 (UART-RX) of the DMR818S module to pins 2 and 9 of the MCU, respectively.

Note that UART communication is bidirectional. When connecting, the TX pin of the module should be connected to the RX pin of the MCU, and the RX pin of the module should be connected to the TX pin of the MCU. This is essential for enabling two-way communication.

4.Control Pin Connection
Pin 13 (CS) of the DMR818S is the sleep enable pin, and pin 14 (PTT) is the transmit/receive control pin.

 Connect the control pins (CS, PTT) of the DMR818S to available GPIO pins on the MCU. In this case, the MCU uses pin 13 and pin 14 to connect to pin 13 and pin 14 of the DMR818S, respectively. In the MCU software configuration, ensure that pin 13 is set as an output to control the CS pin’s high/low state. Similarly, pin 14 should be configured via software to generate the necessary signals for transmit and receive control through the PTT pin.

5.Antenna Connection
Ensure that the antenna interface of the DMR818S is properly connected to an external antenna (connected to pin 7) to maintain communication quality.

During the connection process, always follow the pin definitions and connection methods specified in the datasheet to avoid incorrect wiring that could damage the device. Pay attention to signal direction and voltage level matching to ensure stable and reliable communication. By following these steps, you should be able to successfully connect the DMR818S radio module to an external MCU and achieve the intended communication functionality.

If you need further assistance or have any questions, please refer to the relevant documentation or contact NiceRF technical support.