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CMT2300A Module

Technical details

Property Value
Name CMT2300A
Frequency 868MHz
Product Info Link
Datasheet Link


The CMT2300A module is a 868MHz RF module. It is important to get a module which supports SPI communication. Currently only the EBYTE E49-900M20S is supported as a standalone module, or use the OpenDTUFusion integrated PCB instead.

The CMT2300A uses 3-Wire half duplex SPI communication. Due to this fact it currently requires a separate SPI bus. If you want to run the CMT2300A module on the same ESP32 as a NRF24L01+ module or a PCD8544 display make sure you get a ESP which supports 2 SPI busses. Currently the SPI bus host is hardcoded to number 2. This may change in future.

Buy your hardware from a trusted source, at best from a dealer/online shop in your country where you have support and the right to return non-functional hardware. When you want to buy from Amazon, AliExpress, eBay etc., take note that there is a lot of low-quality or fake hardware offered. Read customer comments and ratings carefully!

A heavily incomplete list of shops is:

This list is for your convenience only, the project is not related to any of these shops.


CMT2300a module

CMT2300a module

Pin assignment

The connection pins from the CMT2300A module to the ESP32 module can dynamically configured using Device Profiles (prefered method) or at compile time.

Name in Device Profile Pin Function Description Possible name(s) on PCB
sdio Digital Input/Output SPI Data Input/Output SDIO
clk Digital Input SPI Clock SCLK
cs Digital Input SPI register accesser CSB
fcs Digital Input SPI FIFO accesser FCSB
gpio2 Digital Output Interrupt pin GPIO2
gpio3 Digital Output Interrupt pin GPIO3
Power Power Supply (1,8V - 3.6V) VDD, VCC
Power Ground VSS, GND