📱 SIM800C Development Board

This is a custom development board for the SIM800C GSM module. It is designed for ease of use in prototyping and development, offering all the essential interfaces and features in a compact and practical layout.

💡 Features

• On-board USB to Serial Converter (CH340N): Enables direct communication with the SIM800C module via USB Type-C.
• PWRKEY Button: Easily power the module on or off via a dedicated button.
• Micro SIM Card Slot: Convenient slot for inserting a micro SIM card.
• Firmware Upgrade Port: A dedicated USB interface to upgrade the SIM800C firmware directly.
• Audio Interface: Includes a connector for speaker output and microphone input.
• Breakout Pins: All essential SIM800C pins are broken out to a standard 2.54mm header for easy access.

Applications

• IoT (Internet of Things) communication
• SMS / Call-based control systems
• Remote data monitoring
• GSM-based notification systems

Getting Started

1. Insert a micro SIM card into the SIM card holder.
2. Selecting serial communication pins using jumpers.
3. Install the CH340 driver if it's not already installed.
4. Press the PWRKEY button for 1 second to turn on the SIM800C module.
5. There are two ways to communicate with the module :

• Using a on board USB to serial converter for direct communicate with M66 module and Use any serial terminal (like PuTTY or hterm) to communicate with the module via AT commands.
• Using a pin header for communication MCU with M66 module.

Pinout

Pin Name	Description
GND	Ground
+5V	Power
+3V3	Power
MCU RX	The microcontroller's RX pin should be connected to this pin.
MCU TX	The microcontroller's TX pin should be connected to this pin.
DTR	Data Terminal Ready
RING	Incoming Call Indication
PWRKEY	On/Off Module
VRTC	Power supply for RTC
GND	Ground

Notes

• To use the converter, the jumpers must be connected in such a way that TX is connected to cRX and RX is connected to cTX.
• To communicate with the MCU, jumpers must be set so that TX is connected to uRX and RX is connected to uTX.

TX  -> Module Transmit pin
RX  -> Module Receive pin
uRX -> Microcontroller Receive pin
uTX -> Microcontroller Transmit pin
cRX -> CH340n Receive pin
cTX -> CH340n Transmit pin

• The MCURX and MCUTX pins must be connected exactly to the RX and TX pins of the microcontroller and not MCURX to TX and MCUTX to RX.

❌
MCUTX pin --- Microcontroller RX pin
MCURX pin --- Microcontroller TX pin

✅
MCUTX pin --- Microcontroller TX pin
MCURX pin --- Microcontroller RX pin

License

This project is open-source and released under the MIT License.

Author

Designed by Mehrdad Qasemi Taj

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