--- title: M66 Mini DB description: "## Basic Overview The M66 Mini DB is a compact and portable board designed specifically for breadboard. The main equipped modules are the M66 Mini DB series wireless communication modules. ## Feature List ### Module Features - Quad-band: 850/900/1800/1900MHz -…" url: "https://eicut.com/wiki/development-boards/introduction-to-m66-mini-db/" updated: "2026-02-15" category: Development Boards --- # M66 Mini DB ## Basic Overview The M66 Mini DB is a compact and portable board designed specifically for breadboard. The main equipped modules are the M66 Mini DB series wireless communication modules. ## Feature List ### Module Features - Quad-band: 850/900/1800/1900MHz - AT Commands: GSM 07.07, 07.05 and Enhanced AT Commands - TCP/UDP/HTTP/FTP/PPP - Jamming Detection - Audio - FOTA - OpenCPU - QuecFastFix ### MiniDB Features - Compatible with BreadBoard - On Board 2A Switching Regulator - On Board NanoSIM(4FF) socket - Wi-Fi BT - GNSS active antenna circuit   ## Development Board Resources ### Function Description The detailed assignment of the peripheral interfaces on the Development board is as follows:   ![M66 Mini DB — top and bottom view](https://eicut.com/wp-content/uploads/2025/10/image1-1-2-695x1024.webp) **Labeled layout**   | NO. | Name | Silkscreen | Comment | | --- | --- | --- | --- | | **1** | Sim card case | J1 | 4FF SIM Card 12.3 × 8 mm | | **2** | External Bluetooth Antenna | BT ANT | Johanson Bluetooth Antenna | | **3** | External GSM Antenna | GSM ANT | UFL ANTENNA | | **4** | 10pin | P1-P2 | Header 2.54 mm | The Development board has 2 functional indication LEDs, as follows: - **D1**: NETLIGHT - **D2**: Power indication LED.   ### Development Board Interfaces The main pin placement of the Development board is shown in the following figure: ![Annotated pin map of the EICUT M66 Mini DB](https://eicut.com/wp-content/uploads/2025/10/image3-1-2-1024x724.webp) **Pins labeled** | NO. | Name | Silkscreen | Comment | | --- | --- | --- | --- | | **P1-1** | Request to send | RTS | You can use it as an output and input. | | **P1-2** | VRTC | VRTC | Power supply for RTC when VBAT is not supplied for the system. Charging for backup battery or golden capacitor when the VBAT is applied. For the allowed voltage and current values for this pin, see the bottom of the table. | | **P1-3** | RXD | RX | Receive data | | **P1-4** | TXD | TX | Transmit data | | **P1-5** | DCD | DCD | Digital output | | **P1-6** | DTR | DTR | Digital input | | **P1-7** | DBG-TXD | DBGTX | Transmit data | | **P1-8** | DBG-RXD | DBGRX | Receive data | | **P1-9** | TXD-AUX | AUXTX | Transmit data | | **P1-10** | RXD-AUX | AUXRX | Receive data | | **P2-1** | Ground | GND | – | | **P2-2** | CTS | CTS | Clear to send | | **P2-3** | RI | RI | Ring indication | | **P2-4** | ADC0 | ADC | General purpose analog to digital converter. Vmax=2.8V, Vmin=0V | | **P2-5** | SPK1P | SPP | Channel 1 positive voice output | | **P2-6** | SPK1N | SPN | Channel 1 negative voice output | | **P2-7** | MICN | MICN | Negative voice input | | **P2-8** | MICP | MICP | Positive voice input | | **P2-9** | Ground | GND | – | | **P2-10** | Power | +5 | Main power supply of module. Make sure that supply sufficient current in a transmitting burst typically rises to 1.6A. Vmax=4.8V, Vmin=5.5V | VRTC pin voltage: VImax=3.3V, VImin=1.5V, VInorm=2.8V VOmax=3V, VOmin=2V, VOnorm=2.8V IOmax=2mA Iin≈10uA ### Development Board Dimensions ![EICUT M66 Mini DB mechanical dimensions](https://eicut.com/wp-content/uploads/2025/10/image2-1-2-599x1024.webp) **Dimensioned top view in millimeters: 32.6×26 mm**   ## Getting Started Preparation **Step 1**: Install Qnavigator software. 🔗Qnavigator software Click here to [**Download** **QNavigator Software**](https://www.quectel.com/download/qnavigator_v1-5/) **Step 2**: After installation Act like a software wizard. **Step 3**: Connect the Development Board by USB to UART converter to the computer.(pin p1-3, p1-4) Download your driver type according to the USB-to-serial IC model **Step 4**: select your board in the port section, set the baudrate to 115200, and click Connect. **Step 5**: Click on the gear and see if the module is connected. **Step 6**: By entering AT Command, you can use different parts of the module. 🔗Hint Make sure the power supply voltage is stable. The board to power up and turn on automatically without the need for a turn-off function. ## Resource Download - [M66 mini DB schemaic](https://eicut.com/wp-content/uploads/2025/10/M66-mini-DB-schemaic-2.pdf) - [Quectel_M66_GSM_Specification_V1.4.pdf](https://eicut.com/wp-content/uploads/2025/05/Quectel_M66_GSM_Specification_V1.4.pdf) - [Quectel_M66_Hardware_Design_V1.2](https://eicut.com/wp-content/uploads/2025/10/Quectel_M66_Hardware_Design_V1.2.pdf) ## FAQ What is the M66 Mini DB? The **M66 Mini DB** is a compact, breadboard-friendly breakout board for the ultra-small **Quectel M66** module — the world’s smallest Quad-band 2G GSM/GPRS engine with **OpenCPU** and optional **Bluetooth** support. Which frequency bands does it support? Full **Quad-Band**: **850 / 900 / 1800 / 1900 MHz** — global 2G coverage. Does the M66 support Bluetooth and GNSS? **Bluetooth** is supported (with onboard Johanson chip antenna). **GNSS** is not built-in — the board provides a circuit for an external active GNSS antenna if you use a custom M66 variant with GNSS. How to power the M66 Mini DB? Supply **5 V** via the **+5 pin** (P2-10). Onboard **2 A switching regulator** converts it to the required 3.8–4.2 V. Peak current during TX bursts can reach **~1.6–2 A**. Is an external GSM antenna required? Yes — connect a 2G antenna to the **GSM ANT U.FL connector**. No onboard GSM antenna is included. How many UARTs are available? Three UARTs are exposed: • Main UART (TX/RX) • AUX UART (AUXTX/AUXRX) • DBG UART (DBGTX/DBGRX) — useful for firmware debugging and OpenCPU development. Does it support OpenCPU (running code directly on module)? Yes — the M66 is one of the few 2G modules that supports **Quectel OpenCPU**, allowing you to run your own C code directly on the module without an external MCU. What do the LEDs indicate? • **D1 (NETLIGHT)**: Network status (blinking patterns show searching/registered/idle) • **D2**: Power indication (ON when module is powered) What are the board dimensions? Ultra-compact: **32.6 × 26 mm** — ideal for breadboard use and final product integration. How to communicate with the module? Connect via **main UART (TX/RX)** at **115200 bps** using any USB-to-UART adapter or use **QNavigator** / QCOM tools. Full AT command set + Quectel enhanced commands are supported. [![M66 mini Development Board Supporting Quad-band GSM/GPRS/Voice/Bluetooth/QuecFOTATM](https://eicut.com/wp-content/uploads/2025/10/Frame-31_11zon-273x300.webp)](https://eicut.com/product/m66-mini-development-board/)